WEBVTT 00:00:00.080 --> 00:00:01.670 The following content is provided 00:00:01.670 --> 00:00:03.810 under a Creative Commons license. 00:00:03.810 --> 00:00:06.540 Your support will help MIT OpenCourseWare continue 00:00:06.540 --> 00:00:10.150 to offer high quality educational resources for free. 00:00:10.150 --> 00:00:12.690 To make a donation or to view additional materials 00:00:12.690 --> 00:00:16.600 from hundreds of MIT courses, visit MIT OpenCourseWare 00:00:16.600 --> 00:00:21.628 at ocw.mit.edu 00:00:21.628 --> 00:00:23.503 PROFESSOR: All right good afternoon everyone. 00:00:27.830 --> 00:00:31.200 What I have on the board here is what we're going to cover today 00:00:31.200 --> 00:00:33.400 and what we had covered the last time. 00:00:34.830 --> 00:00:38.220 Those in blue here are the ones we have covered the last time 00:00:38.220 --> 00:00:40.810 and the rest of them, five through nine, 00:00:40.810 --> 00:00:43.270 are the ones we are going to cover today. 00:00:43.270 --> 00:00:47.740 Actually the last time I didn't have this last step here, 00:00:47.740 --> 00:00:50.410 dreaming and rapid eye-movement sleep, 00:00:50.410 --> 00:00:53.800 if there is time I want to say a few words about that 00:00:53.800 --> 00:00:56.250 because that's a very interesting topic 00:00:56.250 --> 00:01:01.780 and brings us to make a few comments about Freudian theory. 00:01:06.980 --> 00:01:10.280 All right then so we are going to then start 00:01:10.280 --> 00:01:12.550 with a description of the cortical structures 00:01:12.550 --> 00:01:15.135 that are involved in eye-movement control. 00:01:20.010 --> 00:01:22.160 Now the first thing I want to do is 00:01:22.160 --> 00:01:24.275 to show you once again the monkey brain. 00:01:26.770 --> 00:01:30.400 You're already familiar with those items which are on here. 00:01:30.400 --> 00:01:34.580 Here's V1, here's V4, here's the superior temporal sulcus 00:01:34.580 --> 00:01:38.590 that contains areas MT and MST and of course 00:01:38.590 --> 00:01:41.620 here's the central sulcus, principalis, and the arcuate. 00:01:41.620 --> 00:01:44.810 Another structure involved in eye-movement control 00:01:44.810 --> 00:01:48.930 is the lateral intraparietal sulcus which is in here, 00:01:48.930 --> 00:01:52.600 and then another one is the medial intraparietal sulcus 00:01:52.600 --> 00:01:55.960 but those two perform service similar tasks 00:01:55.960 --> 00:01:59.090 and so I'm not going to talk about the MIP 00:01:59.090 --> 00:02:00.730 separately from LIP. 00:02:00.730 --> 00:02:02.690 And then here in the frontal lobe 00:02:02.690 --> 00:02:06.760 we have the frontal eye fields as the name implies of course, 00:02:06.760 --> 00:02:09.330 it has a lot to do with eye-movement control 00:02:09.330 --> 00:02:11.840 and then here very close to the midline 00:02:11.840 --> 00:02:14.760 we have the medial eye fields which 00:02:14.760 --> 00:02:17.210 also play a role in eye movement control. 00:02:17.210 --> 00:02:19.380 So now we have all these structures 00:02:19.380 --> 00:02:23.170 and this is not by any means totally complete, 00:02:23.170 --> 00:02:26.780 because these deal mostly with saccadic eye movements 00:02:26.780 --> 00:02:29.170 and to a lesser degree with pursuit eye movements 00:02:29.170 --> 00:02:32.650 but the fact is it that all these areas that 00:02:32.650 --> 00:02:35.500 play a significant role in eye-movement control 00:02:35.500 --> 00:02:38.370 and of course, those people who want to understand 00:02:38.370 --> 00:02:41.000 eye-movement control need to figure out 00:02:41.000 --> 00:02:45.790 what these various structures do for you to enable you to look 00:02:45.790 --> 00:02:49.380 around with the great ease that you can look around 00:02:49.380 --> 00:02:50.620 with actually. 00:02:50.620 --> 00:02:55.660 So anyway let's try a number of views 00:02:55.660 --> 00:02:59.680 of how to go about finding out the operational characteristics 00:02:59.680 --> 00:03:02.970 of these areas and furthermore also to find out 00:03:02.970 --> 00:03:03.886 how they interconnect. 00:03:05.400 --> 00:03:10.930 Now one approach that has been very useful in delineating 00:03:10.930 --> 00:03:16.090 the areas in the visual cortex and even in subcortical areas 00:03:16.090 --> 00:03:18.630 is to use electrical stimulation. 00:03:18.630 --> 00:03:21.400 Because it has been found as, as we had discussed 00:03:21.400 --> 00:03:25.200 like the last time that when you electrically stimulate 00:03:25.200 --> 00:03:27.250 some structures heavily involved in eye movement 00:03:27.250 --> 00:03:31.910 control of like the colliculus, at low current levels 00:03:31.910 --> 00:03:35.260 electrical stimulation can elicit a saccade 00:03:35.260 --> 00:03:38.200 and by looking at the characteristics of that 00:03:38.200 --> 00:03:42.100 as we had in the colliculus, you can gain further insight 00:03:42.100 --> 00:03:45.150 about what the roles are of these various areas. 00:03:45.150 --> 00:03:48.130 And of course people have done electrical stimulation 00:03:48.130 --> 00:03:51.580 all over creation in the visual cortex 00:03:51.580 --> 00:03:55.110 as well as in other cortical areas, 00:03:55.110 --> 00:03:58.360 thereby trying to determine whether or not 00:03:58.360 --> 00:04:01.500 the electrical stimulation elicits a motor response 00:04:01.500 --> 00:04:03.910 and of course if you do this in motor cortex 00:04:03.910 --> 00:04:06.830 then you get a motor response and if you do 00:04:06.830 --> 00:04:09.680 do it in areas which is specifically connected 00:04:09.680 --> 00:04:13.060 with eye-movement control you get eye movement. 00:04:13.060 --> 00:04:17.029 So here is an example of the kinds of things we can do. 00:04:17.029 --> 00:04:20.320 Here is a monkey brain and of course 00:04:20.320 --> 00:04:23.080 as we have discussed already, from the brain stem 00:04:23.080 --> 00:04:27.500 the signal is sent to the eye muscles which provides 00:04:27.500 --> 00:04:30.060 the so-called rate code and then above that 00:04:30.060 --> 00:04:33.840 via the superior colliculus and then in the back 00:04:33.840 --> 00:04:38.070 we have V1 that you're already familiar with V2, LIP, 00:04:38.070 --> 00:04:40.460 frontal eye fields, and the medial eye fields. 00:04:40.460 --> 00:04:42.410 So now let's ask the question, what 00:04:42.410 --> 00:04:45.940 happens when you electrically stimulate these cortical areas? 00:04:45.940 --> 00:04:47.580 And also to compare that with what 00:04:47.580 --> 00:04:51.700 happens when you stimulate in the superior colliculus. 00:04:51.700 --> 00:04:56.630 So we already know that when you stimulate the colliculus what 00:04:56.630 --> 00:05:00.040 you get is wherever you put the electrodes in the colliculus 00:05:00.040 --> 00:05:03.670 and you find out where the receptive field is of the cells 00:05:03.670 --> 00:05:06.910 that you will be stimulating, that when you then convert 00:05:06.910 --> 00:05:09.880 and stimulate you get a saccade that brings 00:05:09.880 --> 00:05:14.770 the fovea into the center of the receptive fields of the neurons 00:05:14.770 --> 00:05:17.600 that you are stimulating and that is laid out 00:05:17.600 --> 00:05:22.110 in a nice topographic fashion and that is shown here 00:05:22.110 --> 00:05:24.040 in a schematic fashion. 00:05:24.040 --> 00:05:28.060 So that no matter where the eye starts, at any given point, 00:05:28.060 --> 00:05:29.520 if you electrically stimulate you 00:05:29.520 --> 00:05:33.560 get the same vector saccade in the superior colliculus. 00:05:34.670 --> 00:05:37.360 So you have what is called the vector code which 00:05:37.360 --> 00:05:39.800 if you remember, is quite different from the code 00:05:39.800 --> 00:05:43.860 that you have in the brain stem where you have a rate code. 00:05:43.860 --> 00:05:46.330 So now the question is suppose we now 00:05:46.330 --> 00:05:48.860 start stimulating these other cortical areas 00:05:48.860 --> 00:05:51.860 that I had designated in the previous slide 00:05:51.860 --> 00:05:55.220 and ask the question what happens in those places? 00:05:55.220 --> 00:05:58.840 All right so if you stimulate the visual cortex in this case 00:05:58.840 --> 00:06:03.810 V1 for example, you get the same kind of coding operation, 00:06:03.810 --> 00:06:07.080 you get vector saccades OK, constant vector saccades. 00:06:08.270 --> 00:06:11.210 Then if you do the same thing in LIP 00:06:11.210 --> 00:06:13.940 you also get a constant vector saccade 00:06:13.940 --> 00:06:16.130 and if you do that in the frontal eye fields 00:06:16.130 --> 00:06:17.410 you still get the same thing. 00:06:18.420 --> 00:06:23.490 So all of these areas seem to be coding saccadic vectors 00:06:23.490 --> 00:06:26.970 but now when you stimulate in the medial eye fields 00:06:26.970 --> 00:06:29.590 you get a very different kind of effect. 00:06:29.590 --> 00:06:32.370 Very interesting what you get here 00:06:32.370 --> 00:06:37.990 is what is called a place code, meaning that when you stimulate 00:06:37.990 --> 00:06:41.610 in various regions of the medial eye fields, the eye 00:06:41.610 --> 00:06:45.860 wherever it starts, converges on a particular point which you, 00:06:45.860 --> 00:06:49.480 we'll call the motor field, OK? 00:06:49.480 --> 00:06:53.250 And different regions in the medial eye fields 00:06:53.250 --> 00:06:59.300 have motor fields that generate different locations to which 00:06:59.300 --> 00:07:02.860 the eye will saccade when you stimulate there. 00:07:02.860 --> 00:07:05.545 So that's a very different kind of code from all the others. 00:07:08.190 --> 00:07:11.800 So now the next question is that you're going to pose is, 00:07:11.800 --> 00:07:15.140 how do the signals from all these cortical areas 00:07:15.140 --> 00:07:16.730 get down to the brain stem? 00:07:17.970 --> 00:07:19.510 So what kind of experiment do you 00:07:19.510 --> 00:07:23.470 think you would want to do to get some easy answers to that? 00:07:24.990 --> 00:07:31.870 So to, to perhaps highlight that some people thought, 00:07:31.870 --> 00:07:35.510 that the signals from all of these areas 00:07:35.510 --> 00:07:39.330 go down to the colliculus and then the colliculus sends 00:07:39.330 --> 00:07:42.150 its signals down to the brain stem. 00:07:42.150 --> 00:07:43.970 So if that's the case, what would you, 00:07:43.970 --> 00:07:45.250 what experiment would you do? 00:07:47.790 --> 00:07:49.550 Well the experiment you would do is 00:07:49.550 --> 00:07:52.980 you would remove the superior colliculus OK? 00:07:52.980 --> 00:07:55.110 And then again stimulate all of these areas. 00:07:57.040 --> 00:08:01.600 If that hypothesis, that all these areas send their signals 00:08:01.600 --> 00:08:05.030 through the superior colliculus of the brain stem is correct, 00:08:05.030 --> 00:08:08.950 then you would no longer get any saccades when you electrically 00:08:08.950 --> 00:08:12.680 stimulate in the cortex at any of these sites. 00:08:12.680 --> 00:08:13.740 Got it? 00:08:13.740 --> 00:08:17.790 All right now, let's see if an experiment like that 00:08:17.790 --> 00:08:21.200 had been done and yes, yes it has been. 00:08:21.200 --> 00:08:24.450 So here it is, here we're going to remove 00:08:24.450 --> 00:08:26.080 the superior colliculus. 00:08:26.080 --> 00:08:27.930 All right think about it for a minute, 00:08:27.930 --> 00:08:32.500 think what you would hypothesize will happen? 00:08:32.500 --> 00:08:35.350 Well what happens is quite dramatic. 00:08:35.350 --> 00:08:41.784 When you stimulate in V1, V2, and LIP 00:08:41.784 --> 00:08:42.950 you no longer get a saccade. 00:08:44.120 --> 00:08:47.950 Somehow the signals to generate the saccade from these areas 00:08:47.950 --> 00:08:50.210 seem to be going through the colliculus 00:08:50.210 --> 00:08:52.246 because once the colliculus is not there 00:08:52.246 --> 00:08:53.495 those signals are ineffective. 00:08:54.510 --> 00:08:56.430 Now what happens in the frontal lobe? 00:08:56.430 --> 00:08:59.460 All right what happens there is quite interesting. 00:08:59.460 --> 00:09:02.000 You still get saccades and you still 00:09:02.000 --> 00:09:03.810 get the same coding operation. 00:09:03.810 --> 00:09:05.720 You get a constant vector code when 00:09:05.720 --> 00:09:07.710 you stimulate the frontal eye fields 00:09:07.710 --> 00:09:12.260 and you get your place code in the medial eye fields 00:09:12.260 --> 00:09:14.550 and you get that at the same old threshold. 00:09:14.550 --> 00:09:19.810 So that discovery then resulted in the hypothesis first of all 00:09:19.810 --> 00:09:22.870 that these posterior areas send the signals to the brain 00:09:22.870 --> 00:09:28.020 stem from the colliculus which are called the posterior system 00:09:28.020 --> 00:09:31.630 and the ones in the anterior portions of the brain 00:09:31.630 --> 00:09:33.080 from medial and frontal eye fields 00:09:33.080 --> 00:09:37.290 seem to be able to gain direct access bypassing 00:09:37.290 --> 00:09:41.620 the colliculus to the brain stem is 00:09:41.620 --> 00:09:44.550 because they're still effective when you stimulate there 00:09:44.550 --> 00:09:47.610 and so we can call that the anterior system. 00:09:47.610 --> 00:09:50.960 All right, now of course these two systems 00:09:50.960 --> 00:09:53.643 need to talk to each other, which they do, there are plenty 00:09:53.643 --> 00:09:56.770 of connections there because of course, if you will, 00:09:56.770 --> 00:09:59.860 the left hand, it's got to know what the right hand is doing. 00:09:59.860 --> 00:10:04.100 So anyway this is then a very summary arrangement 00:10:04.100 --> 00:10:07.170 and now we can proceed to ask some questions 00:10:07.170 --> 00:10:10.090 about just what do these various areas do? 00:10:11.350 --> 00:10:13.710 And to understand that data we need 00:10:13.710 --> 00:10:17.320 to look into more detail about the nature 00:10:17.320 --> 00:10:20.130 of electrical stimulation and compare that 00:10:20.130 --> 00:10:25.240 with the nature of eye movements made to visual target. 00:10:25.240 --> 00:10:27.140 So let's look at that next time. 00:10:27.140 --> 00:10:29.330 So we can look at the effects of paired 00:10:29.330 --> 00:10:32.670 electrical and visual stimulation. 00:10:32.670 --> 00:10:36.690 All right so, the first thing we're going to look at 00:10:36.690 --> 00:10:38.620 is what happens when you stimulate 00:10:38.620 --> 00:10:41.990 two sites say in the colliculus at the same time? 00:10:43.200 --> 00:10:46.380 And if you remember, medial is up and lateral is down. 00:10:46.380 --> 00:10:49.420 So if you stimulate each of those alone 00:10:49.420 --> 00:10:53.730 you get here in number one you get an upward saccade, 00:10:53.730 --> 00:10:55.950 you simulate number two you get a downward saccade. 00:10:57.150 --> 00:10:59.330 Now the question comes up, what happens 00:10:59.330 --> 00:11:02.430 when you stimulate both at the same time? 00:11:02.430 --> 00:11:05.070 Well the number of hypotheses that 00:11:05.070 --> 00:11:08.390 have been proposed and by now it's been well established 00:11:08.390 --> 00:11:12.890 that what happened is that you get a vector average saccade 00:11:12.890 --> 00:11:16.530 not vector summation, but vector averaging OK? 00:11:16.530 --> 00:11:18.770 Now, to prove that that is indeed 00:11:18.770 --> 00:11:22.350 vector averaging if you take the same experiment 00:11:22.350 --> 00:11:25.130 but you put one electrode in the anterior 00:11:25.130 --> 00:11:28.340 portion and the other electrode in the posterior 00:11:28.340 --> 00:11:30.890 one of the colliculus, this one of course 00:11:30.890 --> 00:11:34.120 generates a small saccade and this one a large saccade. 00:11:34.120 --> 00:11:35.920 So if its vector averages, you should 00:11:35.920 --> 00:11:37.690 get an in-between saccade. 00:11:37.690 --> 00:11:40.460 If your vector sums then it should get a bigger saccade 00:11:40.460 --> 00:11:42.960 than either of those and you indeed 00:11:42.960 --> 00:11:45.280 get a vector average saccade. 00:11:45.280 --> 00:11:47.260 So depending on this arrangement, 00:11:47.260 --> 00:11:51.060 or this arrangement, you get the same vector average saccade 00:11:51.060 --> 00:11:54.690 because the only thing that's happening here 00:11:54.690 --> 00:11:58.910 is you excite the neurons in the colliculus 00:11:58.910 --> 00:12:00.725 by virtue of this electrical stimulation. 00:12:02.440 --> 00:12:04.330 Now think about that for a minute. 00:12:04.330 --> 00:12:08.890 If this were the case with visual stimuli, 00:12:08.890 --> 00:12:11.440 suppose two visual stimuli come up, 00:12:11.440 --> 00:12:13.020 it would be a total disaster if you 00:12:13.020 --> 00:12:16.570 made an eye movement between the two of them wouldn't it? 00:12:16.570 --> 00:12:18.960 So somehow there's some mechanisms 00:12:18.960 --> 00:12:23.810 in the brain that force you, force you, 00:12:23.810 --> 00:12:28.580 I guess that may not be the right word, 00:12:28.580 --> 00:12:31.610 achieve the ability to select one 00:12:31.610 --> 00:12:33.420 or the other of the visual targets 00:12:33.420 --> 00:12:37.490 accurately and not be vector averaging it. 00:12:37.490 --> 00:12:41.950 Now to accomplish that logically speaking, what you need 00:12:41.950 --> 00:12:45.360 is some inhibitory circuits and the mechanism 00:12:45.360 --> 00:12:49.570 for selection and then a decision as to where to look. 00:12:49.570 --> 00:12:52.630 All right so to highlight that let 00:12:52.630 --> 00:12:55.060 me just say one more thing about electrical stimulation. 00:12:55.060 --> 00:12:57.960 This is true what I told you about vector averaging 00:12:57.960 --> 00:13:03.500 with electrical stimulation even when you stimulate the two, 00:13:03.500 --> 00:13:07.240 the two superior colliculi or two different locations 00:13:07.240 --> 00:13:11.200 in the brain each of those gives you an eye movement 00:13:11.200 --> 00:13:13.610 into the left or right hemifield and yet 00:13:13.610 --> 00:13:15.340 they also vector average. 00:13:15.340 --> 00:13:17.120 So now let's look at what happens 00:13:17.120 --> 00:13:21.840 when a similar situation is used in a real experiment where 00:13:21.840 --> 00:13:25.880 the monkey looks at visual targets and so what you do here 00:13:25.880 --> 00:13:30.050 is you present these two targets at the same time. 00:13:30.050 --> 00:13:32.770 And so the monkey in a sense has to make a decision 00:13:32.770 --> 00:13:36.290 or you have to make a decision as to where to look. 00:13:36.290 --> 00:13:38.980 And as long as there's a nice big separation here 00:13:38.980 --> 00:13:42.480 which is 90 degrees in this case, what you can see here 00:13:42.480 --> 00:13:45.640 are the real eye movements that half the time the monkey looks 00:13:45.640 --> 00:13:47.520 to the left, half the time to the right 00:13:47.520 --> 00:13:50.370 and it makes very very few in-between saccades. 00:13:50.370 --> 00:13:52.240 Whereas if you electrically stimulated 00:13:52.240 --> 00:13:54.390 at these sites in the colliculus you'd 00:13:54.390 --> 00:13:56.000 get a vector average saccade just 00:13:56.000 --> 00:13:59.665 like what I've shown you here OK? 00:14:02.370 --> 00:14:06.460 All right so now that being the case, 00:14:06.460 --> 00:14:09.350 we can move on and ask some additional questions 00:14:09.350 --> 00:14:12.710 about what happens when you bring the two 00:14:12.710 --> 00:14:15.980 stimuli closer together, all right? 00:14:15.980 --> 00:14:19.020 The closer together they get the more difficult 00:14:19.020 --> 00:14:21.650 it is to make an independent decision 00:14:21.650 --> 00:14:25.230 as to whether to look to the left or the right target that 00:14:25.230 --> 00:14:27.470 comes up above the fixation spot. 00:14:27.470 --> 00:14:30.750 So here's an example of that, actually what 00:14:30.750 --> 00:14:32.410 I'm going to do is this. 00:14:32.410 --> 00:14:36.100 Let me delay for a little bit what happens with that 00:14:36.100 --> 00:14:39.220 and first I want to tell you about what 00:14:39.220 --> 00:14:42.320 happens with various kinds of lesions 00:14:42.320 --> 00:14:44.420 that you make on eye movements and then we'll 00:14:44.420 --> 00:14:47.910 talk about this question of the angular 00:14:47.910 --> 00:14:50.085 separation between the two visual targets. 00:14:51.250 --> 00:14:56.600 So therefore let's do-- the reason I want to do this first 00:14:56.600 --> 00:14:59.400 is to give you sort of a real sense when you 00:14:59.400 --> 00:15:04.150 do very informal kind of testing and by informal testing what 00:15:04.150 --> 00:15:07.890 I mean is that you're going to see a monkey actually 00:15:07.890 --> 00:15:10.090 perform eye movements OK? 00:15:11.680 --> 00:15:17.530 So here we are, here's a monkey, here's his brain so to speak 00:15:17.530 --> 00:15:21.490 and this is what we call of course an intact animal and now 00:15:21.490 --> 00:15:24.250 what I'm going to do, I'm going to start the movie for you 00:15:24.250 --> 00:15:26.030 to see what kinds of eye movements 00:15:26.030 --> 00:15:30.010 he makes when we present some apple pieces for the monkey 00:15:30.010 --> 00:15:31.010 to eat. 00:15:31.010 --> 00:15:32.040 OK are you ready? 00:15:32.040 --> 00:15:32.660 Here it is. 00:15:40.740 --> 00:15:42.200 Can everybody see this OK? 00:15:49.610 --> 00:15:52.570 So you can see that when an apple piece appears 00:15:52.570 --> 00:15:56.780 the monkey makes a saccade to it and grabs it and stuffs 00:15:56.780 --> 00:15:58.950 in his mouth and eats it. 00:15:58.950 --> 00:16:02.180 OK so that's what a normal monkey does 00:16:02.180 --> 00:16:06.010 with his fully intact, functional brain. 00:16:06.010 --> 00:16:08.650 So now we're going to ask the question, what 00:16:08.650 --> 00:16:13.370 happens if you take out the colliculus on one side, 00:16:13.370 --> 00:16:16.620 meaning a unilaterally lesion, what happens to the eye 00:16:16.620 --> 00:16:21.010 movements the monkey makes subsequent to such a lesion? 00:16:21.010 --> 00:16:22.610 Are you ready for that? 00:16:22.610 --> 00:16:23.546 Here we are. 00:16:23.546 --> 00:16:24.420 It's the same monkey. 00:16:27.382 --> 00:16:28.965 You can see that his eye movements may 00:16:28.965 --> 00:16:32.750 be a little bit slower perhaps but he still looks to the left 00:16:32.750 --> 00:16:34.750 and to the right quite well. 00:16:37.200 --> 00:16:40.950 He tends to sort of look towards the side of the lesion when 00:16:40.950 --> 00:16:45.190 there's no stimulus OK, but other than that he seems 00:16:45.190 --> 00:16:49.340 to make really rather, rather good eye movement in spite 00:16:49.340 --> 00:16:52.410 of the fact that he has a colliculus missing on one side. 00:16:54.780 --> 00:17:01.130 So what that means is that just looking at what the monkey does 00:17:01.130 --> 00:17:04.390 in this qualitative manner is not 00:17:04.390 --> 00:17:10.640 going to tell you too much about what these various structures 00:17:10.640 --> 00:17:15.720 do and so consequently you have to carry out some more 00:17:15.720 --> 00:17:20.490 refined experiments to determine what kinds of deficits 00:17:20.490 --> 00:17:24.180 do arise when you take out the colliculus, you take out 00:17:24.180 --> 00:17:29.710 other cortical structures for the generation of eye movement. 00:17:29.710 --> 00:17:34.430 So let me first of all tell you about a really interesting 00:17:34.430 --> 00:17:38.550 finding that was made that had nothing 00:17:38.550 --> 00:17:40.890 to do with the colliculus at the time it was made, 00:17:40.890 --> 00:17:44.990 was a strictly behavioral study much of it done on humans. 00:17:44.990 --> 00:17:48.530 What was done is first of all a fixation spot came on 00:17:48.530 --> 00:17:50.990 and then a single target appeared 00:17:50.990 --> 00:17:54.050 and often what was done is that the fixation spot was turned 00:17:54.050 --> 00:17:59.560 off just a few milliseconds before the target came 00:17:59.560 --> 00:18:03.760 on and on each trial it appeared someplace else OK? 00:18:03.760 --> 00:18:07.010 So then you've collected a lot of data 00:18:07.010 --> 00:18:11.030 to see what is the nature of the monkey's eye movements 00:18:11.030 --> 00:18:17.210 and in particular that initial study examined by Fischer 00:18:17.210 --> 00:18:21.170 and Boch, examined what the latency distribution was 00:18:21.170 --> 00:18:23.710 of the eye movements made and they made 00:18:23.710 --> 00:18:26.990 an incredible discovery that they subsequently generated 00:18:26.990 --> 00:18:30.500 hundreds of studies published in numerous journals, 00:18:30.500 --> 00:18:32.850 and this is the discovery. 00:18:32.850 --> 00:18:36.320 Here we have the latency of saccades made 00:18:36.320 --> 00:18:38.840 and here's a number of saccades and what 00:18:38.840 --> 00:18:41.260 you get is a bimodal distribution 00:18:41.260 --> 00:18:44.380 of saccadic latencies, amazing. 00:18:44.380 --> 00:18:47.030 They call the first mode, which takes 00:18:47.030 --> 00:18:50.290 place in the latency of average latency for bright stimulus 00:18:50.290 --> 00:18:55.450 over about 100 milliseconds, called express saccades. 00:18:55.450 --> 00:18:58.380 The second mode they called regular saccades and that 00:18:58.380 --> 00:19:02.950 took about I don't know, 135, 140 milliseconds 00:19:02.950 --> 00:19:03.640 on the average. 00:19:04.800 --> 00:19:07.750 So that got this bimodal distribution 00:19:07.750 --> 00:19:12.670 and so people said, my goodness what could this be due to? 00:19:12.670 --> 00:19:14.540 How do we explain this effect? 00:19:14.540 --> 00:19:16.560 What other cortical or subcortical 00:19:16.560 --> 00:19:19.920 mechanisms that give rise to a bimodal distribution 00:19:19.920 --> 00:19:20.890 of saccadic latencies? 00:19:21.940 --> 00:19:24.360 As I've said a huge number of experiments 00:19:24.360 --> 00:19:27.440 had been carried out to find this out. 00:19:27.440 --> 00:19:30.800 So when one group of investigators 00:19:30.800 --> 00:19:33.986 saw this phenomenon and they did experiments 00:19:33.986 --> 00:19:35.360 with monkey's and they found this 00:19:35.360 --> 00:19:38.750 is a real effect everywhere, these findings were initially 00:19:38.750 --> 00:19:42.320 made in Germany and even, even in the United States 00:19:42.320 --> 00:19:44.430 you get a bimodal distribution of saccades 00:19:44.430 --> 00:19:46.830 in both humans and monkeys. 00:19:46.830 --> 00:19:52.500 So once it was established as a really solid effect 00:19:52.500 --> 00:19:56.080 people began to speculate as to what are the neural, 00:19:56.080 --> 00:19:57.040 underlying mechanisms? 00:19:58.580 --> 00:20:02.940 And as I've told you earlier it was 00:20:02.940 --> 00:20:11.580 noted that based on those lesion studies of the colliculus which 00:20:11.580 --> 00:20:15.540 eliminated saccades from the posterior portion of the cortex 00:20:15.540 --> 00:20:19.330 but not from the interior, that there 00:20:19.330 --> 00:20:24.940 is a reasonable hypothesis involved in proposing that you 00:20:24.940 --> 00:20:29.320 have a posterior system and an anterior system. 00:20:29.320 --> 00:20:32.220 And so when people saw this they said aha, 00:20:32.220 --> 00:20:34.990 now we know why we have these two systems. 00:20:34.990 --> 00:20:37.320 One is for making rapid saccades and the other 00:20:37.320 --> 00:20:39.380 is to making regular saccades. 00:20:39.380 --> 00:20:43.020 And so they proposed that the posterior system does 00:20:43.020 --> 00:20:47.060 one of these and the anterior system does the other. 00:20:47.060 --> 00:20:50.550 Well that was a nice hypothesis but so often 00:20:50.550 --> 00:20:55.020 when it comes to hypotheses as to how the brain works, 00:20:55.020 --> 00:20:59.270 often most of the time the hypotheses end up being wrong 00:20:59.270 --> 00:21:02.870 and so what you need to do rather than just hypothesize is 00:21:02.870 --> 00:21:05.290 to actually carry out experiments 00:21:05.290 --> 00:21:07.440 to test the hypothesis. 00:21:07.440 --> 00:21:10.540 So what is the test of this hypothesis? 00:21:10.540 --> 00:21:12.206 What would you do as an experimentalist? 00:21:15.400 --> 00:21:17.112 Well, yes. 00:21:19.036 --> 00:21:21.922 AUDIENCE: You could ablate either posterior 00:21:21.922 --> 00:21:23.860 or the anterior pathways. 00:21:23.860 --> 00:21:25.880 PROFESSOR: Very good you could ablate. 00:21:25.880 --> 00:21:27.660 All right so one thing you can do 00:21:27.660 --> 00:21:32.460 first of all you can ablate the superior colliculus even 00:21:32.460 --> 00:21:39.800 though when you saw that just with regular easy test just 00:21:39.800 --> 00:21:43.880 filming it, you didn't see much of a deficit. 00:21:43.880 --> 00:21:47.642 You sort of sense that maybe the monkey's a bit slower but other 00:21:47.642 --> 00:21:49.140 than that it wasn't that clear. 00:21:49.140 --> 00:21:51.110 But if you take out the colliculus 00:21:51.110 --> 00:21:55.170 then you eliminate the posterior system in essence all right, 00:21:55.170 --> 00:21:57.886 and so the question is what happens when you do that? 00:21:57.886 --> 00:21:59.260 And then you can ask the question 00:21:59.260 --> 00:22:02.760 what happens when you take out some other cortical areas? 00:22:02.760 --> 00:22:03.850 So let's look at this. 00:22:06.240 --> 00:22:11.880 Here we have a monkey 10 weeks after the colliculus has been 00:22:11.880 --> 00:22:14.510 ablated, we're talking about a major effect here 00:22:14.510 --> 00:22:17.640 that doesn't recover, and you took out 00:22:17.640 --> 00:22:21.090 the colliculus on one side on the left OK, 00:22:21.090 --> 00:22:23.910 so that controls rightward saccades 00:22:23.910 --> 00:22:26.920 and therefore when you look at the leftward saccades that's 00:22:26.920 --> 00:22:28.980 to the intact side of the brain you 00:22:28.980 --> 00:22:31.100 get the usual bimodal distribution 00:22:31.100 --> 00:22:32.810 of saccadic latencies. 00:22:32.810 --> 00:22:35.460 But then when you look at rightward saccades 00:22:35.460 --> 00:22:39.160 Lo and behold, you don't see a single express saccade 00:22:39.160 --> 00:22:40.660 and even the regular saccades have 00:22:40.660 --> 00:22:45.822 a longer latency than the ones to they intact side 00:22:45.822 --> 00:22:47.530 and these are collected at the same time. 00:22:47.530 --> 00:22:49.940 The monkey's sitting there with his head fixed 00:22:49.940 --> 00:22:51.740 and sometimes a target appears on the left 00:22:51.740 --> 00:22:54.960 sometimes on the right and you collect hundreds of thousands 00:22:54.960 --> 00:22:59.190 of trials that way and you test this over various time periods 00:22:59.190 --> 00:23:03.720 and this is at least 10 weeks, 2 and 1/2 months after the lesion 00:23:03.720 --> 00:23:05.950 and even if you test the monkey a year 00:23:05.950 --> 00:23:08.390 later you still get the same effect. 00:23:08.390 --> 00:23:11.100 So this clearly points out the fact 00:23:11.100 --> 00:23:15.400 that your ability to make these rapid reflex-like saccades 00:23:15.400 --> 00:23:19.980 is something that's got to go through the superior colliculus 00:23:19.980 --> 00:23:21.260 OK? 00:23:21.260 --> 00:23:25.090 So now we can ask the question, well, what about if one 00:23:25.090 --> 00:23:28.310 makes lesions in the frontal and medial eye fields? 00:23:28.310 --> 00:23:31.713 All right so think about that for a minute what would 00:23:31.713 --> 00:23:32.213 you predict? 00:23:35.710 --> 00:23:38.170 All right so here we go. 00:23:38.170 --> 00:23:41.110 We take out the frontal eye fields in this case, ready? 00:23:42.830 --> 00:23:44.400 Oops let me go back. 00:23:45.690 --> 00:23:47.390 We take out the frontal eye fields 00:23:47.390 --> 00:23:52.090 but to give you a sense of this overall effect first of all 00:23:52.090 --> 00:23:56.520 let's just do the same informal testing that I've shown you 00:23:56.520 --> 00:23:59.460 before with the colliculus and see 00:23:59.460 --> 00:24:01.600 what the movie looks like OK? 00:24:01.600 --> 00:24:04.660 Here's a monkey not as handsome as the other one, 00:24:04.660 --> 00:24:08.040 but what you do here is a person behind 00:24:08.040 --> 00:24:10.100 there sometimes just presents a target 00:24:10.100 --> 00:24:13.000 and sometimes just moves it around so the monkey tracks it, 00:24:13.000 --> 00:24:13.770 can you see that? 00:24:15.370 --> 00:24:17.566 And what I shouldn't have told you which one I feel 00:24:17.566 --> 00:24:18.315 have been ablated. 00:24:19.920 --> 00:24:26.490 Look at how nicely he tracks on both sides, 00:24:26.490 --> 00:24:29.040 grabs it, puts it in his, stuffs it in his mouth 00:24:29.040 --> 00:24:32.620 and so the monkey seems to be perfectly fine with making 00:24:32.620 --> 00:24:37.630 saccades to either side and perfectly fine making pursuit 00:24:37.630 --> 00:24:41.240 eye movements either direction, indicating 00:24:41.240 --> 00:24:45.740 that this informal testing doesn't reveal anything truly 00:24:45.740 --> 00:24:50.090 obvious about the deficit that you have in eye movement 00:24:50.090 --> 00:24:52.630 control when you take out the frontal eye fields. 00:24:52.630 --> 00:24:55.490 So therefore you again need to go on 00:24:55.490 --> 00:24:59.090 to carry out some more careful experiments 00:24:59.090 --> 00:25:03.320 to obtain some detailed quantitative data. 00:25:03.320 --> 00:25:05.380 So let's look at that. 00:25:05.380 --> 00:25:09.010 First of all let's go back and look at express saccades. 00:25:09.010 --> 00:25:11.670 You take out the frontal eye fields and Lo and behold, 00:25:11.670 --> 00:25:14.990 you still get express saccades indicating 00:25:14.990 --> 00:25:20.780 that that is definitely specific for the posterior system 00:25:20.780 --> 00:25:23.670 even further if you do this experiment what 00:25:23.670 --> 00:25:26.680 you find if you take out both the medial and frontal eye 00:25:26.680 --> 00:25:29.310 fields you still get it, you still 00:25:29.310 --> 00:25:31.130 get your express saccades. 00:25:31.130 --> 00:25:35.130 So clearly these two areas are not directly involved 00:25:35.130 --> 00:25:38.330 in generating quick rapid saccadic eye movements 00:25:38.330 --> 00:25:42.270 and it's still bimodal so that initial hypothesis 00:25:42.270 --> 00:25:44.290 that the first mode is the colliculus 00:25:44.290 --> 00:25:47.250 and the second posterior system the colliculus 00:25:47.250 --> 00:25:51.570 and the second mode is the anterior system 00:25:51.570 --> 00:25:52.990 is clearly totally wrong. 00:25:55.560 --> 00:25:57.430 All right so that's what then happens 00:25:57.430 --> 00:26:01.810 and once this has been done, you say, well, you've 00:26:01.810 --> 00:26:04.690 got to find something that the frontal eye and the medial eye 00:26:04.690 --> 00:26:05.450 fields are doing. 00:26:05.450 --> 00:26:08.330 So let's come up with some other experiments 00:26:08.330 --> 00:26:13.120 to see whether the monkey is selective for anything else 00:26:13.120 --> 00:26:16.610 when it comes to lesions of the frontal and the medial eye 00:26:16.610 --> 00:26:17.580 fields. 00:26:17.580 --> 00:26:22.460 All right so one thing that had been proposed 00:26:22.460 --> 00:26:27.070 is that maybe the important factor is some high level eye 00:26:27.070 --> 00:26:32.130 movement activity such as making saccades in quick succession 00:26:32.130 --> 00:26:35.870 to successive targets that are out there OK? 00:26:35.870 --> 00:26:38.760 So the way that can be done quantitatively 00:26:38.760 --> 00:26:41.790 is you have the monkey first fixate OK, 00:26:41.790 --> 00:26:45.220 and after they fixate you present the target 00:26:45.220 --> 00:26:47.310 and then you present the second target. 00:26:47.310 --> 00:26:50.330 So the monkey has to make two successive saccades 00:26:50.330 --> 00:26:52.670 and what you can do is you can vary 00:26:52.670 --> 00:26:56.900 the temporal delay between their succession. 00:26:56.900 --> 00:27:02.540 So the monkey then has to make a plan to makes two saccades 00:27:02.540 --> 00:27:05.820 because these two stimuli appear before the monkey starts 00:27:05.820 --> 00:27:09.130 his initial saccade when the temporal interval is short. 00:27:09.130 --> 00:27:11.420 So then the monkey somehow knows it's easier 00:27:11.420 --> 00:27:15.840 to do, he has to do this even though he starts a saccade only 00:27:15.840 --> 00:27:19.740 after the two targets have come on when they are presented 00:27:19.740 --> 00:27:22.810 indeed in the short, the short latency. 00:27:22.810 --> 00:27:25.900 So that's what happens and of course in different trials 00:27:25.900 --> 00:27:28.560 you have different kinds of pairings like that 00:27:28.560 --> 00:27:31.115 and if you do that what you find is very interesting 00:27:31.115 --> 00:27:33.250 here are the four conditions, this 00:27:33.250 --> 00:27:37.650 shows the monkey's performance 18 weeks post 00:27:37.650 --> 00:27:39.890 left frontal eye field lesion and this shows it 00:27:39.890 --> 00:27:44.420 60 weeks after and it shows this to the intact side 00:27:44.420 --> 00:27:47.160 and the side where the frontal eye fields are missing 00:27:47.160 --> 00:27:49.240 and what you can see very dramatically 00:27:49.240 --> 00:27:52.540 is that the monkey really has difficulties 00:27:52.540 --> 00:27:58.820 in making a plan to execute two saccades in a row. 00:27:58.820 --> 00:28:02.880 Quite dramatic effect significant [INAUDIBLE] one 00:28:02.880 --> 00:28:06.970 level, of course indicating that the frontal eye fields 00:28:06.970 --> 00:28:10.750 play a role in planning sequences of eye movements. 00:28:10.750 --> 00:28:15.860 Now then another, well this I want to show you, 00:28:15.860 --> 00:28:19.560 what happens with the, when you compare 00:28:19.560 --> 00:28:21.770 the effects of the frontal eye field 00:28:21.770 --> 00:28:24.510 lesions and the medial eye field lesion 00:28:24.510 --> 00:28:29.210 and this is done over various sequence durations 00:28:29.210 --> 00:28:35.030 and for several weeks and what you find is that in both cases 00:28:35.030 --> 00:28:38.170 there is a recovery but the effect 00:28:38.170 --> 00:28:41.600 is much, much more dramatic with the frontal eye field lesion 00:28:41.600 --> 00:28:43.540 than a medial eye field lesion. 00:28:44.840 --> 00:28:47.640 So indeed there's for the frontal eye 00:28:47.640 --> 00:28:50.080 fields we can say the frontal eye fields play 00:28:50.080 --> 00:28:53.680 an important role in planning sequences of eye movements 00:28:53.680 --> 00:28:58.440 which is sort of a high level activity in executing 00:28:58.440 --> 00:29:00.110 saccadic eye movements. 00:29:00.110 --> 00:29:06.070 Now then what we can do is to examine what 00:29:06.070 --> 00:29:10.840 about making a decision of where to look when 00:29:10.840 --> 00:29:14.020 more than one target comes up and the simplest form of that 00:29:14.020 --> 00:29:17.769 is that you present two targets like that OK? 00:29:17.769 --> 00:29:19.560 And so the monkey has to make a decision am 00:29:19.560 --> 00:29:21.970 I going to look to the left or to the right? 00:29:21.970 --> 00:29:24.240 And then what you do is you can vary 00:29:24.240 --> 00:29:32.510 the temporal delay between the two like that, or like that OK? 00:29:32.510 --> 00:29:35.350 And then you can do that again either to intact 00:29:35.350 --> 00:29:37.180 parts of the visual field or those 00:29:37.180 --> 00:29:40.470 where either frontal eye fields or some other structure 00:29:40.470 --> 00:29:41.450 is missing. 00:29:41.450 --> 00:29:43.710 All right so let's look at what happens. 00:29:43.710 --> 00:29:46.620 Here is what we have is the intact monkey 00:29:46.620 --> 00:29:49.020 this part I've shown you before. 00:29:49.020 --> 00:29:51.970 All right this is when the two targets come 00:29:51.970 --> 00:29:55.330 on simultaneously and in this case 00:29:55.330 --> 00:29:58.550 the left target comes on 34 milliseconds before the right 00:29:58.550 --> 00:30:00.360 and here's the reverse and what you 00:30:00.360 --> 00:30:04.010 can see that even a 34 millisecond delay causes 00:30:04.010 --> 00:30:08.840 the monkey to very much prefer to go to the, to the target, 00:30:08.840 --> 00:30:13.090 make a saccade to the target that had appeared first. 00:30:13.090 --> 00:30:16.620 So that's what happens in a normal intact monkey. 00:30:16.620 --> 00:30:20.680 Now we can ask the next related questions still 00:30:20.680 --> 00:30:22.350 in the normal intact monkey, what 00:30:22.350 --> 00:30:24.870 happens when you put the two stimuli closer together? 00:30:25.900 --> 00:30:29.010 OK so here's an example they're, now they're separated only 00:30:29.010 --> 00:30:32.630 by 40 degrees and here the data again it 00:30:32.630 --> 00:30:37.530 shows that when it's, in this case 67 milliseconds apart 00:30:37.530 --> 00:30:39.700 the monkey chooses almost exclusively 00:30:39.700 --> 00:30:41.640 the target that comes on first. 00:30:41.640 --> 00:30:45.270 When they're simultaneous what happens is interesting, 00:30:45.270 --> 00:30:47.980 you get some so-called vector average saccades 00:30:47.980 --> 00:30:50.870 that you always get with electrical stimulation. 00:30:50.870 --> 00:30:54.140 So those you get, it's still a minority of the saccades. 00:30:54.140 --> 00:30:56.530 And the closer you bring the two together, 00:30:56.530 --> 00:30:59.480 the more frequent will be the vector average saccades. 00:30:59.480 --> 00:31:02.440 When they're only separated by set 10 degrees 00:31:02.440 --> 00:31:04.960 they will be all vector average saccades So this 00:31:04.960 --> 00:31:08.900 is what happens in the normal monkey you 00:31:08.900 --> 00:31:12.168 get this nice bimodal distribution and vector 00:31:12.168 --> 00:31:14.126 average saccades when the two are simultaneous. 00:31:15.290 --> 00:31:19.370 Now let's ask the question what happens when you take out 00:31:19.370 --> 00:31:23.360 a cortical structure in this case the frontal eye fields 00:31:23.360 --> 00:31:26.930 and here we are you take out the left frontal eye fields. 00:31:26.930 --> 00:31:30.280 These above are the same the data I just shown you 00:31:30.280 --> 00:31:35.190 adding a bigger delay here, just to make it even clearer that 00:31:35.190 --> 00:31:37.590 by that time the monkey never chooses 00:31:37.590 --> 00:31:39.180 the target that comes on second. 00:31:40.530 --> 00:31:45.690 And here we have the monkey after left frontal eye field 00:31:45.690 --> 00:31:48.300 lesion and look at what, what happens. 00:31:48.300 --> 00:31:52.000 What happens is that the monkey at 0 00:31:52.000 --> 00:31:56.790 chooses 100% saccade to the intact side OK. 00:31:56.790 --> 00:31:59.860 There seem to be a little bit of a shift here 00:31:59.860 --> 00:32:02.870 and then when they're 100 milliseconds, 00:32:02.870 --> 00:32:04.370 then you have an equal distribution. 00:32:05.420 --> 00:32:09.980 So to equalize the choice that the brain makes 00:32:09.980 --> 00:32:13.170 you have to now because of the missing frontal eye fields, 00:32:13.170 --> 00:32:18.950 present one of the targets a 100 milliseconds earlier 00:32:18.950 --> 00:32:23.500 on the affected side to get the same kind of distribution 00:32:23.500 --> 00:32:25.560 that you get in the intact monkey. 00:32:25.560 --> 00:32:27.870 So this further highlights the fact 00:32:27.870 --> 00:32:32.660 that the frontal eye fields play a significant role 00:32:32.660 --> 00:32:40.595 in making decisions about the selection of visual targets. 00:32:42.350 --> 00:32:46.260 All right now we can look at this more quantitatively. 00:32:46.260 --> 00:32:54.270 This shows the distribution of choices OK, to the left target, 00:32:54.270 --> 00:32:56.702 this is the intact monkey preoperative 00:32:56.702 --> 00:32:58.660 and then when you take out the left frontal eye 00:32:58.660 --> 00:33:03.670 fields it's a huge movement over the equal choices 00:33:03.670 --> 00:33:08.420 has to be about 130 milliseconds separated 00:33:08.420 --> 00:33:11.590 with the affected side getting the target a 130 milliseconds 00:33:11.590 --> 00:33:12.330 earlier. 00:33:12.330 --> 00:33:15.690 Then if you keep doing this there's some recovery 00:33:15.690 --> 00:33:19.795 but even four years later you still have a huge effect. 00:33:21.320 --> 00:33:23.220 Now you can ask the question what 00:33:23.220 --> 00:33:26.750 if you do the same experiment in the medial eye fields? 00:33:26.750 --> 00:33:29.600 And so if you do that you first of all get a small effect 00:33:29.600 --> 00:33:34.600 to begin with and after just 16 weeks there's full recovery. 00:33:34.600 --> 00:33:36.780 So obviously the medial eye fields 00:33:36.780 --> 00:33:40.710 don't, do not seem to play a central role 00:33:40.710 --> 00:33:44.140 in making decisions as to which target 00:33:44.140 --> 00:33:45.980 to look at when more than one target appears 00:33:45.980 --> 00:33:47.490 in the visual field. 00:33:47.490 --> 00:33:52.620 All right so now having done that quantitative work 00:33:52.620 --> 00:33:54.990 indicating that the frontal eye fields play 00:33:54.990 --> 00:33:57.070 an important role in target selection 00:33:57.070 --> 00:33:59.450 and the sequencing of eye movements. 00:33:59.450 --> 00:34:01.150 We can move on and ask the question, 00:34:01.150 --> 00:34:04.690 well we talked about the posterior 00:34:04.690 --> 00:34:06.775 system and the anterior system. 00:34:09.070 --> 00:34:12.500 Is it true that there are these two systems? 00:34:12.500 --> 00:34:16.110 Or are there many more systems that we're not aware of? 00:34:17.400 --> 00:34:20.214 This should remind you of the fact 00:34:20.214 --> 00:34:21.880 that it had been proposed when we talked 00:34:21.880 --> 00:34:26.510 about extrastriate cortex that area of V4 00:34:26.510 --> 00:34:36.020 essential for processing high level activity including color, 00:34:36.020 --> 00:34:42.340 whereas the area MT and MST play an important role in emotion 00:34:42.340 --> 00:34:44.380 and so it was purported that these two 00:34:44.380 --> 00:34:48.139 major systems in the posterior cortex, the medial and lateral 00:34:48.139 --> 00:34:48.909 if you will. 00:34:51.290 --> 00:34:55.080 So the question was raised if you remove both of these areas, 00:34:55.080 --> 00:35:03.190 meaning the gateway to these areas, V4 and MT what happens? 00:35:03.190 --> 00:35:05.970 And when you do that they still the monkey's 00:35:05.970 --> 00:35:09.830 able to do a lot of things indicating that we have more 00:35:09.830 --> 00:35:15.690 pathways from V1 than just these two the anterior, the medial 00:35:15.690 --> 00:35:16.750 and the lateral. 00:35:16.750 --> 00:35:18.590 So now the question is what about when 00:35:18.590 --> 00:35:20.250 it comes to this eye movement control? 00:35:21.972 --> 00:35:23.680 We should do the same kind of experiment. 00:35:25.180 --> 00:35:28.850 We should remove the colliculus that supposedly eliminates 00:35:28.850 --> 00:35:32.380 the posterior system and then we should remove the frontal eye 00:35:32.380 --> 00:35:37.190 fields bilaterally, that eliminates the anterior system. 00:35:37.190 --> 00:35:41.580 So now the question is what happens when you do that? 00:35:41.580 --> 00:35:44.810 And again, we going to turn to the informal test, 00:35:44.810 --> 00:35:46.880 meaning we going to, we going to take 00:35:46.880 --> 00:35:51.674 a movie of the monkey who has these areas removed. 00:35:51.674 --> 00:35:54.340 Think about it for a minute what do you think's going to happen? 00:35:56.630 --> 00:35:58.280 OK so here's the monkey. 00:35:58.280 --> 00:35:58.780 Ready? 00:36:06.780 --> 00:36:15.700 The monkey sees well, he makes his movements with his hands 00:36:15.700 --> 00:36:19.940 quite accurately but what, what happens to the eyes, 00:36:19.940 --> 00:36:21.310 you watching the eyes right? 00:36:22.350 --> 00:36:23.055 No eye movement. 00:36:24.110 --> 00:36:25.152 Everybody see this? 00:36:25.152 --> 00:36:26.110 Should I show it again? 00:36:31.150 --> 00:36:33.090 The monkey makes no eye movements. 00:36:33.090 --> 00:36:36.260 He cannot make eye movements because his natural tendency 00:36:36.260 --> 00:36:38.930 would be just like I'd seen in the previous movies that he 00:36:38.930 --> 00:36:45.260 makes eye movements to the apple pieces so he can grab them. 00:36:45.260 --> 00:36:47.440 He still pays attention to them everything 00:36:47.440 --> 00:36:51.520 is fine except he doesn't move his eyes because he can't move 00:36:51.520 --> 00:36:54.630 his eyes as a result of having eliminated these two 00:36:54.630 --> 00:36:57.500 systems and because of that we can say 00:36:57.500 --> 00:37:02.400 with confidence that it's, as far as the visual as far 00:37:02.400 --> 00:37:06.300 as the ocular motor system is concerned we indeed have 00:37:06.300 --> 00:37:10.630 these two major pathways which when they're eliminated 00:37:10.630 --> 00:37:13.690 eliminates their ability to move, 00:37:13.690 --> 00:37:15.670 make saccadic eye movements. 00:37:15.670 --> 00:37:22.530 OK now let's go back to the effect 00:37:22.530 --> 00:37:29.130 of electrical stimulation to gain further insight about what 00:37:29.130 --> 00:37:31.310 these various areas do and what you 00:37:31.310 --> 00:37:34.160 can do in these experiments is not only 00:37:34.160 --> 00:37:37.990 to stimulate at a high level to elicit a saccade 00:37:37.990 --> 00:37:41.820 but you can simulate at a lower level 00:37:41.820 --> 00:37:46.540 and then pair that with the appearance of a visual target. 00:37:46.540 --> 00:37:51.610 This then enables you to see whether there's summation here 00:37:51.610 --> 00:37:54.720 or if there's interference, so let's look at that. 00:37:55.940 --> 00:37:58.240 All right here is again a monkey brain 00:37:58.240 --> 00:38:00.970 and what I'm going to tell you is what happens when you 00:38:00.970 --> 00:38:04.980 do this experiment in V1, in LIP, and in the frontal eye 00:38:04.980 --> 00:38:08.310 fields, even maybe I think I may have something 00:38:08.310 --> 00:38:09.900 also in the medial eye fields. 00:38:09.900 --> 00:38:13.640 All right so let me describe the experimental procedure for you 00:38:13.640 --> 00:38:16.060 so that you understand how these kinds of experiments 00:38:16.060 --> 00:38:17.280 are conducted. 00:38:17.280 --> 00:38:20.370 You put an electrode in to any of these structures 00:38:20.370 --> 00:38:23.050 and you find the receptive field first all right? 00:38:23.050 --> 00:38:26.200 Once you've found the receptive field you electrically 00:38:26.200 --> 00:38:28.610 stimulate then you confirm the fact 00:38:28.610 --> 00:38:33.020 that the electrical stimulation brings the fovea 00:38:33.020 --> 00:38:36.990 into the receptive field of the simulated neuron's when 00:38:36.990 --> 00:38:40.000 you do this in all the areas except in the medial eye 00:38:40.000 --> 00:38:40.770 fields. 00:38:40.770 --> 00:38:45.690 Then what you do is you actually present the visual target there 00:38:45.690 --> 00:38:46.560 OK? 00:38:46.560 --> 00:38:51.830 And lastly you present two visual targets 00:38:51.830 --> 00:38:54.180 and you electrically stimulate to see 00:38:54.180 --> 00:38:58.920 how it biases your choice as a result of this 00:38:58.920 --> 00:39:02.570 in most cases sub-threshold electrical stimulation. 00:39:02.570 --> 00:39:06.490 So if you do that what you find is, first of all, 00:39:06.490 --> 00:39:09.740 if you do this experiment with a intact monkey 00:39:09.740 --> 00:39:15.400 without stimulation you find say a receptive field here 00:39:15.400 --> 00:39:19.110 and then you simply see what the monkey's choices are left 00:39:19.110 --> 00:39:21.920 to the right and what you plot here 00:39:21.920 --> 00:39:25.979 is the saccades made to the target in the receptive field 00:39:25.979 --> 00:39:27.770 and what you can see is what I've shown you 00:39:27.770 --> 00:39:31.380 before namely when the targets are simultaneous then 00:39:31.380 --> 00:39:34.440 the monkey chooses left or right with equal probability. 00:39:35.640 --> 00:39:38.625 Now we're going to add the electrical stimulation 00:39:38.625 --> 00:39:42.960 and ask the question can we shift the curve to the left? 00:39:42.960 --> 00:39:44.940 If you shift it to the left, that 00:39:44.940 --> 00:39:47.780 means that the electrical stimulation facilitated 00:39:47.780 --> 00:39:52.020 the choice and if you shift to the right it means that it 00:39:52.020 --> 00:39:55.470 caused interference, it lessened the chances 00:39:55.470 --> 00:39:57.560 of the monkey making a saccade into that area, 00:39:57.560 --> 00:40:00.540 meaning the stimulation created inhibition. 00:40:00.540 --> 00:40:01.570 Got it? 00:40:01.570 --> 00:40:04.580 All right, so here's an example in the lower 00:40:04.580 --> 00:40:09.980 layers of V1 remember in layer six of area 00:40:09.980 --> 00:40:14.740 V1 is where you have your complex cells that project down 00:40:14.740 --> 00:40:16.070 to the superior colliculus. 00:40:16.070 --> 00:40:19.590 So here if you stimulate at sub-threshold levels and some 00:40:19.590 --> 00:40:23.220 of these are very low levels only 7 1/2 and 10 microamps. 00:40:23.220 --> 00:40:26.180 OK, really very, very fine currents 00:40:26.180 --> 00:40:28.710 using themselves going to elicit an eye movement. 00:40:28.710 --> 00:40:32.400 So if you do that the stimulation created 00:40:32.400 --> 00:40:35.450 a significant, highly significant facilitatory 00:40:35.450 --> 00:40:36.050 affect. 00:40:36.050 --> 00:40:38.070 This is in the lower layers. 00:40:38.070 --> 00:40:41.730 Now if you do the same experiment in the upper layers 00:40:41.730 --> 00:40:45.800 you get the opposite effect we get a gigantic even-- look 00:40:45.800 --> 00:40:50.670 at this five and 10 microamps, --even at that low, incredibly 00:40:50.670 --> 00:40:54.220 low level you get a gigantic interference effect. 00:40:54.220 --> 00:40:59.660 So that says that there's a complex interplay in V1 00:40:59.660 --> 00:41:02.700 in the decision process that arises 00:41:02.700 --> 00:41:04.785 as to whether you're going to look at a target, 00:41:04.785 --> 00:41:07.250 or whether you're not going to look at a target. 00:41:07.250 --> 00:41:10.230 Now we can do the same experiment in LIP 00:41:10.230 --> 00:41:13.550 and in some regions you get this huge facilitatory effect 00:41:13.550 --> 00:41:16.470 and in other regions you get an inhibitory effect, 00:41:16.470 --> 00:41:17.890 so that's LIP. 00:41:17.890 --> 00:41:21.850 So therefore this structure also plays a significant role 00:41:21.850 --> 00:41:24.720 in deciding whether to look at or not 00:41:24.720 --> 00:41:27.970 to look at a visual stimulus and here it 00:41:27.970 --> 00:41:31.930 shows that in LIP as you increase the current 00:41:31.930 --> 00:41:35.430 you get a gigantic increase in the latency 00:41:35.430 --> 00:41:38.330 in these inhibitory areas with which 00:41:38.330 --> 00:41:42.360 a saccade can be generated indicating that LIP plays 00:41:42.360 --> 00:41:45.552 an important role in whether you're 00:41:45.552 --> 00:41:47.510 going to look at a target or whether you're not 00:41:47.510 --> 00:41:48.860 going to look at target. 00:41:48.860 --> 00:41:51.560 OK and then if you do the frontal eye fields 00:41:51.560 --> 00:41:53.370 everywhere in the frontal eye fields 00:41:53.370 --> 00:41:56.830 you get a huge facilitatory effect 00:41:56.830 --> 00:42:03.560 and in the medial eye fields you also get a facilitatory effect 00:42:03.560 --> 00:42:08.170 as long as the motor field is where 00:42:08.170 --> 00:42:09.410 the visual target appears. 00:42:10.540 --> 00:42:13.510 But now you can remember what I told you about the medial eye 00:42:13.510 --> 00:42:17.390 fields the fact is that they have a place code. 00:42:17.390 --> 00:42:19.710 So one can do a different experiment 00:42:19.710 --> 00:42:26.170 in which instead of presenting the target in the motor field 00:42:26.170 --> 00:42:34.780 you can present the fixation spot there. 00:42:34.780 --> 00:42:39.030 So here again to remind you, we have this place code. 00:42:39.030 --> 00:42:41.550 So now we do this experiment, just 00:42:41.550 --> 00:42:44.040 like what I've shown you before just to repeat it, 00:42:44.040 --> 00:42:49.320 in this case the target appears and that causes a facilitation 00:42:49.320 --> 00:42:52.660 in this case we put the fixation spot in there 00:42:52.660 --> 00:42:56.720 and the location of the target's just displaced 00:42:56.720 --> 00:42:59.620 and when you do that you get a huge inhibitory 00:42:59.620 --> 00:43:04.700 effect because somehow the electrical stimulation forces 00:43:04.700 --> 00:43:10.300 the animal keep the eye at the location where the motor 00:43:10.300 --> 00:43:13.870 field is in the medial eye fields 00:43:13.870 --> 00:43:16.410 and this is a very important point 00:43:16.410 --> 00:43:20.710 and it means that the medial eye fields plays a significant role 00:43:20.710 --> 00:43:23.940 in deciding how long to look at a target 00:43:23.940 --> 00:43:25.550 before making the next saccade. 00:43:27.940 --> 00:43:32.410 OK so now we going to, there's a lot of facts, so 00:43:32.410 --> 00:43:34.580 and you're going to get some more lot of facts. 00:43:34.580 --> 00:43:36.530 So now I'm going to summarize what I told you 00:43:36.530 --> 00:43:39.220 about the effects of sub-threshold electrical 00:43:39.220 --> 00:43:41.080 stimulation OK? 00:43:41.080 --> 00:43:44.560 If you stimulate in the upper layers of V1 and V2, 00:43:44.560 --> 00:43:47.490 V2 I should add to this you get interference, 00:43:47.490 --> 00:43:51.760 in the lower layers you get facilitation in V4 there was 00:43:51.760 --> 00:43:55.910 no effect I didn't talk about that before in LIP you can get 00:43:55.910 --> 00:43:59.950 both facilitation interference and also fixation increase. 00:43:59.950 --> 00:44:02.720 In the frontal eye fields you get facilitation 00:44:02.720 --> 00:44:04.880 and the medial eye fields depending 00:44:04.880 --> 00:44:07.840 on how you set it up you can get facilitation 00:44:07.840 --> 00:44:12.010 if the target appears in the motor field 00:44:12.010 --> 00:44:16.910 and you get inhibition when it appear, 00:44:16.910 --> 00:44:19.550 when the fixation spot appears in it. 00:44:19.550 --> 00:44:23.850 So that's the basic summary of these effects. 00:44:23.850 --> 00:44:29.130 Now what these findings indicate that somehow 00:44:29.130 --> 00:44:34.670 inhibitory circuits are essential in our ability 00:44:34.670 --> 00:44:38.960 to make saccades to selected visual targets 00:44:38.960 --> 00:44:41.700 and therefore what we want to do is 00:44:41.700 --> 00:44:45.070 to examine what happens when you use 00:44:45.070 --> 00:44:48.490 various kinds of pharmacological agents 00:44:48.490 --> 00:44:56.720 that either facilitate or increase inhibition. 00:44:56.720 --> 00:45:01.760 So to explain that then let me first of all point out to you 00:45:01.760 --> 00:45:04.340 that if you take again the whole brain 00:45:04.340 --> 00:45:08.180 and you look at the colliculus and you look at V1, 00:45:08.180 --> 00:45:11.140 you look at LIP, you look at the frontal eye fields 00:45:11.140 --> 00:45:15.150 you can study these areas by injecting 00:45:15.150 --> 00:45:16.990 two kinds of pharmacological agents, 00:45:16.990 --> 00:45:20.190 bicuculline and muscimol some people believe 00:45:20.190 --> 00:45:23.870 you've heard of this as muscimol I call it muscimol. 00:45:23.870 --> 00:45:25.850 At any rate you all know I'm sure 00:45:25.850 --> 00:45:30.500 but this is bicuculline is a GABA antagonist meaning 00:45:30.500 --> 00:45:35.840 that if you inject it OK, it stops 00:45:35.840 --> 00:45:39.390 the effectiveness of inhibition by GABA. 00:45:39.390 --> 00:45:42.230 Muscimol on the other hand is a GABA agonist 00:45:42.230 --> 00:45:44.720 meaning that if you inject it you 00:45:44.720 --> 00:45:47.740 increase inhibition all right? 00:45:47.740 --> 00:45:50.440 Now I'm sure that all of you must 00:45:50.440 --> 00:45:55.250 have had enough of a background in biochemistry 00:45:55.250 --> 00:45:57.230 to know what these two agents are. 00:46:01.740 --> 00:46:07.840 So now what we can do is we can inject 00:46:07.840 --> 00:46:13.840 either one or the other of these agents and assess two things. 00:46:13.840 --> 00:46:15.580 First off we assess eye movements 00:46:15.580 --> 00:46:18.090 and secondly we also have to obviously assess 00:46:18.090 --> 00:46:19.910 how it affects your visual ability. 00:46:21.010 --> 00:46:23.450 So let's move on and do this. 00:46:25.270 --> 00:46:28.200 The first set of experiments done with this 00:46:28.200 --> 00:46:31.640 was by Hikosaka and Woods many years ago in the colliculus. 00:46:34.280 --> 00:46:38.100 So what they did, very clever beautiful experiment, 00:46:38.100 --> 00:46:42.180 is that they would put a microelectrode 00:46:42.180 --> 00:46:45.640 into the colliculus and then initially just stimulate 00:46:45.640 --> 00:46:48.590 to see what kind of eye movement you get and then they 00:46:48.590 --> 00:46:54.580 would inject either muscimol or what's the other agent? 00:46:56.302 --> 00:46:57.270 AUDIENCE: [INAUDIBLE] 00:46:57.270 --> 00:47:00.090 PROFESSOR: Very good and see what happens. 00:47:00.090 --> 00:47:02.355 Now which of those causes more inhibition? 00:47:03.590 --> 00:47:04.530 AUDIENCE: [INAUDIBLE] 00:47:09.230 --> 00:47:13.190 PROFESSOR: OK, so let's look at that then. 00:47:13.190 --> 00:47:15.550 If you electrically stimulate just like I've shown you 00:47:15.550 --> 00:47:19.100 before you get a constant vector saccade no matter 00:47:19.100 --> 00:47:21.585 where the eye starts you get the same vector. 00:47:22.620 --> 00:47:25.630 Now the question is what happens to the spontaneous eye 00:47:25.630 --> 00:47:32.300 movements of the monkey when you first inject muscimol OK? 00:47:32.300 --> 00:47:37.220 Which is an agent that mimics if you will your GABA, 00:47:37.220 --> 00:47:40.050 meaning it increases inhibition and what happens 00:47:40.050 --> 00:47:43.010 is that the monkey hardly ever makes a saccade 00:47:43.010 --> 00:47:46.170 with the vectors represented by the area that 00:47:46.170 --> 00:47:47.640 has been injected. 00:47:47.640 --> 00:47:52.280 By contrast if you inject bicuculline 00:47:52.280 --> 00:47:56.790 the monkey keeps making saccades with that vector even when 00:47:56.790 --> 00:47:59.330 there's nothing out there like the release of area 00:47:59.330 --> 00:48:00.530 for inhibition. 00:48:00.530 --> 00:48:03.070 And the signal is sent down to the brain step move your eye, 00:48:03.070 --> 00:48:05.230 move your eye, move your eye, move your eye, 00:48:05.230 --> 00:48:06.530 that's what happens. 00:48:06.530 --> 00:48:12.860 So to show this in more detail then 00:48:12.860 --> 00:48:18.140 we can ask what happens when you use two behavioral tasks OK, 00:48:18.140 --> 00:48:20.140 the so-called paired target task that we already 00:48:20.140 --> 00:48:22.740 talked about quite a bit and you talk 00:48:22.740 --> 00:48:25.540 about a visual discrimination task 00:48:25.540 --> 00:48:27.380 and that one is that you're already 00:48:27.380 --> 00:48:30.470 familiar with the so-called audited task you present 00:48:30.470 --> 00:48:34.340 several stimuli one of which is different from the others. 00:48:34.340 --> 00:48:38.580 All right so here is an example of the paired target task. 00:48:38.580 --> 00:48:41.740 What we do here again we vary the temporal asynchrony 00:48:41.740 --> 00:48:43.340 between the two targets just like what 00:48:43.340 --> 00:48:45.320 I've shown with the electrical stimulation 00:48:45.320 --> 00:48:47.940 and this is the monkey's normal behavior when the two 00:48:47.940 --> 00:48:53.190 targets are simultaneous the monkey chooses each randomly. 00:48:54.440 --> 00:48:59.050 Now let's ask the question what happens is again to remind you, 00:48:59.050 --> 00:49:02.290 if it goes this way the curve goes this way it's facilitation 00:49:02.290 --> 00:49:05.620 if the current curve goes that way we get interference. 00:49:05.620 --> 00:49:09.520 So let's ask what happens first of all, no let me also tell you 00:49:09.520 --> 00:49:12.760 about the oddity task just to make sure that you have it. 00:49:12.760 --> 00:49:16.020 All right that's the oddity task you know that already. 00:49:16.020 --> 00:49:19.520 All right so we can now go on and first examine 00:49:19.520 --> 00:49:22.790 what happens with muscimol or muscimol 00:49:22.790 --> 00:49:25.120 or whatever you prefer to use OK? 00:49:25.120 --> 00:49:27.651 Well again what, what does this agent do? 00:49:27.651 --> 00:49:29.150 Does it do excitation or inhibition? 00:49:30.314 --> 00:49:31.610 AUDIENCE: Inhibition. 00:49:31.610 --> 00:49:35.710 PROFESSOR: Very good, inhibition because it mimics GABA 00:49:35.710 --> 00:49:36.430 all right? 00:49:36.430 --> 00:49:38.120 So let's look at what happens. 00:49:38.120 --> 00:49:41.300 Here we have a normal monkey same experiment 00:49:41.300 --> 00:49:45.980 as before, here is the this is V1, 00:49:45.980 --> 00:49:48.880 here's a receptive field you present one visual target 00:49:48.880 --> 00:49:51.760 there, the other there, then you vary the temporary asynchrony 00:49:51.760 --> 00:49:56.330 between them, this is what happens in the normal case OK? 00:49:56.330 --> 00:50:00.120 Now you're going to inject the muscimol 00:50:00.120 --> 00:50:01.800 and ask yourself the question, we 00:50:01.800 --> 00:50:04.490 increased inhibition what do you think is going to happen? 00:50:04.490 --> 00:50:06.100 Well it should be pretty obvious, 00:50:06.100 --> 00:50:09.120 what happens is you get gigantic inhibition 00:50:09.120 --> 00:50:11.190 the monkey practically never looks 00:50:11.190 --> 00:50:14.880 at here because that area is not being activated 00:50:14.880 --> 00:50:18.690 by the visual stimulus because of the inhibition. 00:50:18.690 --> 00:50:22.520 Then if you do this over time, even four hours later there's 00:50:22.520 --> 00:50:24.790 a huge, huge effect but by the next day 00:50:24.790 --> 00:50:28.690 the monkey recovers luckily so one can do this experiment 00:50:28.690 --> 00:50:31.860 several times because this agent is something 00:50:31.860 --> 00:50:33.780 that washes out of the brain. 00:50:33.780 --> 00:50:36.870 All right so now let's look at what 00:50:36.870 --> 00:50:38.780 happens in the frontal eye fields. 00:50:38.780 --> 00:50:42.560 Same experiment, all right, just a different location 00:50:42.560 --> 00:50:43.597 with the electrode. 00:50:43.597 --> 00:50:45.430 And what you get, this is your preinjection. 00:50:46.510 --> 00:50:49.970 And once again, after the injection, 00:50:49.970 --> 00:50:52.390 you get a big interference effect 00:50:52.390 --> 00:50:54.120 which recovers by the next day. 00:50:55.410 --> 00:50:57.850 So that is what you get that with that. 00:50:57.850 --> 00:51:02.010 Then let's examine what happens in LIP. 00:51:03.280 --> 00:51:05.990 Curiously in LIP there was no effect. 00:51:07.220 --> 00:51:07.720 All right. 00:51:07.720 --> 00:51:13.640 So now let's next turn to the so-called oddity task meaning 00:51:13.640 --> 00:51:16.900 several stimuli, one of which is different from the others 00:51:16.900 --> 00:51:21.230 and what is the monkey's ability to choose 00:51:21.230 --> 00:51:22.970 the different stimulus. 00:51:22.970 --> 00:51:26.260 So if you do this with a muscimol injection 00:51:26.260 --> 00:51:29.260 there's a huge deficit for V1 that you 00:51:29.260 --> 00:51:32.720 would expect because it destroyed the monkey's ability 00:51:32.720 --> 00:51:35.250 to analyze the visual stimulus that 00:51:35.250 --> 00:51:37.840 appeared in the receptive field. 00:51:37.840 --> 00:51:40.870 Then if you do the same thing in the frontal eye fields 00:51:40.870 --> 00:51:45.110 you find a mild deficit and then if you do the same thing in LIP 00:51:45.110 --> 00:51:47.800 you get no deficit at all. 00:51:47.800 --> 00:51:51.960 So this is what then happens with the oddities task 00:51:51.960 --> 00:51:55.860 and now what you can do is ask what happens when instead 00:51:55.860 --> 00:51:59.410 of muscimol we're going to inject bicuculline? 00:52:01.920 --> 00:52:04.560 And we're going to go through the same procedure 00:52:04.560 --> 00:52:10.529 as what I just shown you and so we start here in V1 00:52:10.529 --> 00:52:12.570 and when you do that think about it for a minute, 00:52:12.570 --> 00:52:15.680 now you're facilitating supposedly 00:52:15.680 --> 00:52:17.370 because you're eliminating inhibition 00:52:17.370 --> 00:52:18.703 what do you think you would get? 00:52:19.560 --> 00:52:22.150 Well, you'll be in for a surprise, what 00:52:22.150 --> 00:52:25.230 you get is gigantic interference again 00:52:25.230 --> 00:52:30.400 because putting bicuculline in also screwed up you're 00:52:30.400 --> 00:52:35.370 ability in the visual cortex to analyze the visual percept. 00:52:36.510 --> 00:52:39.700 This again recovers over time by the next day 00:52:39.700 --> 00:52:41.020 it's back to normal. 00:52:41.020 --> 00:52:43.719 Then if you do the same experiment in the frontal eye 00:52:43.719 --> 00:52:45.510 fields what do you think's going to happen? 00:52:45.510 --> 00:52:47.670 Can you predict what's going to happen just 00:52:47.670 --> 00:52:48.660 looking at this slide? 00:52:49.900 --> 00:52:53.753 Why do you think this is such a big empty space here huh? 00:52:55.110 --> 00:53:01.550 OK well look at that, when you put in bicuculline we 00:53:01.550 --> 00:53:03.066 get this incredible facilitation. 00:53:04.180 --> 00:53:07.300 OK the monkey just like in the colliculus 00:53:07.300 --> 00:53:12.340 barely can help himself to make a saccade into the field 00:53:12.340 --> 00:53:20.170 that has been disinhibited OK?, and that again recovers, 00:53:20.170 --> 00:53:22.100 bicuculline is washed out more rapidly 00:53:22.100 --> 00:53:24.900 than muscimol and by the next day 00:53:24.900 --> 00:53:26.750 certainly is back to normal. 00:53:26.750 --> 00:53:29.200 Now we can do the same thing just looking 00:53:29.200 --> 00:53:33.490 at the eye movements themselves to further highlight 00:53:33.490 --> 00:53:35.140 what I've shown you before. 00:53:35.140 --> 00:53:38.670 If you'd put bicuculline in OK, in the frontal eye fields 00:53:38.670 --> 00:53:44.290 the monkey cannot help but make saccades with similar vectors 00:53:44.290 --> 00:53:49.410 that are represented by the neurons in the injected site 00:53:49.410 --> 00:53:52.320 and that's why you have all this is its full stack of saccades 00:53:52.320 --> 00:53:55.290 buh, buh, buh, buh, bang the monkey just can't help 00:53:55.290 --> 00:53:59.301 but makes saccades because the signal to make the saccade has 00:53:59.301 --> 00:54:00.050 been disinhibited. 00:54:01.660 --> 00:54:06.000 All right so then you can ask what happens in LIP 00:54:06.000 --> 00:54:09.420 and when you do that you get no effect at all, 00:54:09.420 --> 00:54:14.200 and if you do now the bicuculline injection 00:54:14.200 --> 00:54:16.880 with the oddities task we can once again 00:54:16.880 --> 00:54:19.150 ask well what happens with that? 00:54:19.150 --> 00:54:23.530 And then once again as I've already indicated, 00:54:23.530 --> 00:54:28.020 both bicuculline and muscimol cause a major interference 00:54:28.020 --> 00:54:34.340 in your ability to select the odd target, 00:54:34.340 --> 00:54:37.780 in other words to visually discriminate, 00:54:37.780 --> 00:54:40.220 but if you do the same thing in the frontal eye fields 00:54:40.220 --> 00:54:44.460 and in the medial and LIP you get no effect at all. 00:54:47.110 --> 00:54:52.820 So what this then says to summarize all right 00:54:52.820 --> 00:54:53.575 is the following. 00:54:54.960 --> 00:54:57.640 We talk about target selection, which was a two target 00:54:57.640 --> 00:55:00.930 task, individual discrimination which was the oddities task 00:55:00.930 --> 00:55:03.950 and here we have muscimol and here bicuculline. 00:55:03.950 --> 00:55:07.810 So if you do that in the frontal eye field, in V1 first, 00:55:07.810 --> 00:55:10.920 you get interference, you do it in the frontal eye 00:55:10.920 --> 00:55:12.900 fields you get interference of muscimol 00:55:12.900 --> 00:55:16.630 with great facilitation, with bicuculline 00:55:16.630 --> 00:55:18.430 and LIP has no effec. 00:55:18.430 --> 00:55:20.850 And then, just to remind you, it has already 00:55:20.850 --> 00:55:23.110 been shown by Hikosaka and Woods, 00:55:23.110 --> 00:55:25.690 that you get interference of facilitation 00:55:25.690 --> 00:55:28.770 in the superior colliculus with these two agents. 00:55:28.770 --> 00:55:31.220 You do the same thing with visual discrimination, 00:55:31.220 --> 00:55:34.350 you get a major deficit in V1 for both 00:55:34.350 --> 00:55:41.070 and you get a mild effect for both actually no effect 00:55:41.070 --> 00:55:42.820 really with bicuculline in the frontal eye 00:55:42.820 --> 00:55:46.140 fields and no effect at all in LIP. 00:55:46.140 --> 00:55:49.120 So these manipulations then gives you 00:55:49.120 --> 00:55:54.470 sort of a sense of what these various areas do 00:55:54.470 --> 00:55:56.780 in the generation of eye movements 00:55:56.780 --> 00:55:59.830 that involve not only just to make a saccade to a target 00:55:59.830 --> 00:56:03.780 but to select targets individual field, make a decision as 00:56:03.780 --> 00:56:08.820 to where to look, and also to decide when to look, 00:56:08.820 --> 00:56:10.700 because any time you make an eye movement 00:56:10.700 --> 00:56:14.270 and I should've mentioned that more thoroughly before, you 00:56:14.270 --> 00:56:16.840 look at something and how long you look at it 00:56:16.840 --> 00:56:19.890 depends on how long it takes you to analyze what you're looking 00:56:19.890 --> 00:56:20.465 at. 00:56:20.465 --> 00:56:24.480 Now in most cases it takes you maybe I 00:56:24.480 --> 00:56:27.220 don't know 200 milliseconds or less to say, 00:56:27.220 --> 00:56:30.310 oh yeah that's letter a or whatever 00:56:30.310 --> 00:56:35.677 and then you say it's your brain mechanisms tell you, OK, now 00:56:35.677 --> 00:56:36.510 you know what it is. 00:56:36.510 --> 00:56:38.830 It's OK for you to move your eye. 00:56:38.830 --> 00:56:42.000 OK so that's involved and then thirdly, 00:56:42.000 --> 00:56:44.710 you have an important task in making sequences 00:56:44.710 --> 00:56:46.490 of eye movements so that when you 00:56:46.490 --> 00:56:49.910 look at a picture like the movie I showed you in the beginning 00:56:49.910 --> 00:56:53.300 in the previous lecture, when you look at something 00:56:53.300 --> 00:56:55.480 then you make a decision as to where to look next, 00:56:55.480 --> 00:56:57.970 where to look next and if you keep doing this 00:56:57.970 --> 00:57:01.310 for I don't know 20, 30 saccades then you get to a state 00:57:01.310 --> 00:57:02.730 where you say oh now I understand 00:57:02.730 --> 00:57:03.750 the picture as a whole. 00:57:04.860 --> 00:57:08.350 All right so now we're going to summarize 00:57:08.350 --> 00:57:11.560 what the tasks are in a very simple situation 00:57:11.560 --> 00:57:13.870 and what brain structures are involved in it. 00:57:13.870 --> 00:57:15.990 First of all let's imagine that you're 00:57:15.990 --> 00:57:20.780 looking at fixation spot designated by a. 00:57:20.780 --> 00:57:23.240 Let's assume the two stimuli come on 00:57:23.240 --> 00:57:26.110 and that means that you have to make a decision as 00:57:26.110 --> 00:57:28.310 to what those two targets are, you 00:57:28.310 --> 00:57:31.770 have to identify them because you have to select one of those 00:57:31.770 --> 00:57:32.400 OK? 00:57:32.400 --> 00:57:35.100 Of course in most cases you're talking about many targets that 00:57:35.100 --> 00:57:38.860 are out there this is a highly simplified version. 00:57:38.860 --> 00:57:41.510 The next step is to decide which of these two 00:57:41.510 --> 00:57:45.130 targets now that I know one says a and the other says b, which 00:57:45.130 --> 00:57:49.030 of those two targets, actually b and c in the picture here 00:57:49.030 --> 00:57:50.960 which of these targets should I look at, 00:57:50.960 --> 00:57:54.470 and so you make a decision all right, that generates 00:57:54.470 --> 00:57:58.530 excitation and inhibitin, inhibition through excitatory 00:57:58.530 --> 00:58:00.880 and inhibitory circuits, and then you 00:58:00.880 --> 00:58:03.400 decide OK we going to look here and that 00:58:03.400 --> 00:58:06.920 means that you have to decide which one not to look 00:58:06.920 --> 00:58:09.640 at in addition to deciding which one to look at, 00:58:09.640 --> 00:58:13.930 because you've got to make an accurate saccade so you 00:58:13.930 --> 00:58:15.810 don't want a vector average. 00:58:15.810 --> 00:58:16.310 All right. 00:58:16.310 --> 00:58:22.500 And then what you need of course is a map, 00:58:22.500 --> 00:58:29.350 if you will, of the motor field so that you can generate 00:58:29.350 --> 00:58:33.610 the appropriate direction of the saccade 00:58:33.610 --> 00:58:36.720 so that you can decide where you're going to look at 00:58:36.720 --> 00:58:40.190 and then lastly as I've mentioned already before, 00:58:40.190 --> 00:58:42.260 you also have to make a decision as 00:58:42.260 --> 00:58:44.880 to when to make that eye movement. 00:58:44.880 --> 00:58:48.620 So now in a very summary fashion we 00:58:48.620 --> 00:58:53.500 can talk about the various brain areas involved. 00:58:53.500 --> 00:58:55.500 Quite a number of different areas 00:58:55.500 --> 00:58:59.570 are involved in the decision as to what these two stimuli are, 00:58:59.570 --> 00:59:02.940 they of course involve much of the visual system including 00:59:02.940 --> 00:59:05.650 also LIP and several other areas. 00:59:05.650 --> 00:59:07.920 Then, then you have to make a decision as 00:59:07.920 --> 00:59:11.470 to which one to look at, again several areas involve notably 00:59:11.470 --> 00:59:14.510 among them are the frontal eye fields, LIP, and also 00:59:14.510 --> 00:59:16.440 the medial eye fields. 00:59:16.440 --> 00:59:20.560 Then you also have to decide which ones not to look at, 00:59:20.560 --> 00:59:23.460 that it was largely the same areas 00:59:23.460 --> 00:59:27.770 and then you need of course a topographic arrangement 00:59:27.770 --> 00:59:30.830 to know where things are and that you 00:59:30.830 --> 00:59:33.890 can find in many areas, including V1, V2, 00:59:33.890 --> 00:59:36.590 the frontal eye fields, and the colliculi which are laid out 00:59:36.590 --> 00:59:39.550 in a nice topographic fashion, and then 00:59:39.550 --> 00:59:42.550 lastly LIP is important for that, 00:59:42.550 --> 00:59:45.190 and I think to some degree also the medial eye fields 00:59:45.190 --> 00:59:49.160 but I'm not sure about that to decide when you should generate 00:59:49.160 --> 00:59:51.090 saccadic eye movements. 00:59:51.090 --> 00:59:52.800 Well that's very nice and makes you 00:59:52.800 --> 00:59:55.160 realize that even though we never 00:59:55.160 --> 00:59:58.940 think about making eye movement all this stuff is going 00:59:58.940 --> 01:00:02.370 on three times a second it's amazing. 01:00:02.370 --> 01:00:05.980 So now you're going to look at what the various visual areas 01:00:05.980 --> 01:00:10.900 and ocular motor areas are that play a role in this OK, 01:00:10.900 --> 01:00:14.300 and so we're going to create a summary diagram. 01:00:14.300 --> 01:00:16.140 So here we have, that's the first one 01:00:16.140 --> 01:00:19.720 I shown you, which has a rate code that from the brain stem 01:00:19.720 --> 01:00:22.930 connects with the eye muscles and activates them. 01:00:22.930 --> 01:00:25.340 Then we have the superior colliculus, 01:00:25.340 --> 01:00:34.420 now the superior colliculus is under strong inhibitory control 01:00:34.420 --> 01:00:37.310 all right, and they're several inhibitory circuits that 01:00:37.310 --> 01:00:46.960 are involved in that and those include the substantia nigra 01:00:46.960 --> 01:00:48.840 that sends inhibitory circuits down 01:00:48.840 --> 01:00:54.830 to the colliculus that then prevents the colliculus 01:00:54.830 --> 01:00:57.190 from generating an eye movement because it 01:00:57.190 --> 01:00:59.350 is under inhibition, because every time you 01:00:59.350 --> 01:01:02.120 look around thousands and thousands 01:01:02.120 --> 01:01:05.670 of impressions impinge on the colliculus 01:01:05.670 --> 01:01:07.800 and you only want one of those to actually get down 01:01:07.800 --> 01:01:09.400 to the deep place, the colliculus, 01:01:09.400 --> 01:01:12.390 to generate an eye movement. 01:01:12.390 --> 01:01:18.410 Now then the substantia nigra is under the control 01:01:18.410 --> 01:01:22.010 of several neural structures which, many of which 01:01:22.010 --> 01:01:24.510 go through this so-called basal ganglia. 01:01:25.880 --> 01:01:29.490 Now we can expand on this and look at the visual input 01:01:29.490 --> 01:01:30.580 to do this. 01:01:30.580 --> 01:01:32.400 We already talked about this a lot 01:01:32.400 --> 01:01:35.350 you, pointed out to you that you have these three 01:01:35.350 --> 01:01:39.290 major, many, many different types of ganglion cells. 01:01:39.290 --> 01:01:40.860 The three major ones we talked about 01:01:40.860 --> 01:01:46.350 are the midget parasol and the so-called W-cells 01:01:46.350 --> 01:01:48.980 that go to the cortex. 01:01:48.980 --> 01:01:52.670 And the W-cells also project directly to the colliculus. 01:01:52.670 --> 01:01:57.310 Then from layer five in the visual cortex 01:01:57.310 --> 01:02:01.410 you have the cells that project to the superior colliculus 01:02:01.410 --> 01:02:09.370 and the intermediate layers and that down flow is controlled 01:02:09.370 --> 01:02:15.370 predominantly by the parasol system as we had described. 01:02:15.370 --> 01:02:17.970 Then we have all these other areas 01:02:17.970 --> 01:02:24.000 that V1 projects to, V2, MT, V4, and so on some of them 01:02:24.000 --> 01:02:27.420 dominated by input from the parasol system 01:02:27.420 --> 01:02:30.060 and others get input from both, and those 01:02:30.060 --> 01:02:33.120 in turn project to the parietal and temporal lobes 01:02:33.120 --> 01:02:37.150 and those in turn have an important influence 01:02:37.150 --> 01:02:41.700 on the inhibitory circuits through the basal ganglia 01:02:41.700 --> 01:02:44.200 and the substantia nigra. 01:02:44.200 --> 01:02:47.700 Now let me finally come to the frontal lobe, the frontal eye 01:02:47.700 --> 01:02:50.640 fields, and the medial eye fields and they in turn 01:02:50.640 --> 01:02:54.520 have direct access to the brain stem 01:02:54.520 --> 01:02:56.920 and also connect to the superior colliculus. 01:02:58.560 --> 01:03:00.600 Now this is still not the whole story 01:03:00.600 --> 01:03:02.450 because what you have in addition is 01:03:02.450 --> 01:03:09.150 a bunch of interconnections among numerous cortical areas 01:03:09.150 --> 01:03:11.950 they talk back and forth to each other 01:03:11.950 --> 01:03:14.590 that enables you to make these decisions as 01:03:14.590 --> 01:03:16.340 to where to look next. 01:03:16.340 --> 01:03:17.730 Now if you think this is complete 01:03:17.730 --> 01:03:21.140 you're still wrong because now what you have to realize 01:03:21.140 --> 01:03:25.530 is that all this circuitry is also 01:03:25.530 --> 01:03:28.161 one that receives input from several other areas, 01:03:28.161 --> 01:03:29.660 with the auditory system that you're 01:03:29.660 --> 01:03:32.860 going to hear a lot about later on in the course, 01:03:32.860 --> 01:03:36.020 the somatosensory system, the olfactory system, 01:03:36.020 --> 01:03:38.370 the smooth pursuit system that we'll mention 01:03:38.370 --> 01:03:40.500 a little bit next time, the vestibular 01:03:40.500 --> 01:03:43.050 system, the accessory optic system we'll 01:03:43.050 --> 01:03:46.290 talk about next time, and the vergence system. 01:03:46.290 --> 01:03:49.950 So all these fit into this incredibly complex circuitry 01:03:49.950 --> 01:03:55.050 already and essential elements in your ability 01:03:55.050 --> 01:03:56.850 to move your eyes about. 01:03:56.850 --> 01:04:04.680 So I think you need to realize therefore that something even 01:04:04.680 --> 01:04:10.040 as simple as just moving your eyes about it's an incredibly 01:04:10.040 --> 01:04:15.510 complicated system involving many structures 01:04:15.510 --> 01:04:19.360 and involving excitatory and inhibitory circuits, 01:04:19.360 --> 01:04:22.130 interconnections it's just, it's almost dumbfounding. 01:04:23.170 --> 01:04:29.050 So that then is the essence of these connections, 01:04:29.050 --> 01:04:31.349 and what I want turn to next I think 01:04:31.349 --> 01:04:32.515 we still have a little time. 01:04:33.600 --> 01:04:37.220 Before I summarize our results for today, 01:04:37.220 --> 01:04:40.723 I want to say something about dreaming and rapid eye 01:04:40.723 --> 01:04:41.222 movements. 01:04:43.958 --> 01:04:49.340 I think all of you know that every night you sleep you dream 01:04:49.340 --> 01:04:51.780 and what you also know that has been discovered more 01:04:51.780 --> 01:04:56.110 recently is when you dream you make rapid eye movement so it's 01:04:56.110 --> 01:05:03.960 called REM sleep, and so the question arose why do we dream? 01:05:03.960 --> 01:05:06.000 Why do we have REM sleep? 01:05:07.560 --> 01:05:16.320 Now, the major influence as to why we dream 01:05:16.320 --> 01:05:19.710 comes from the work of Sigmund Freud who 01:05:19.710 --> 01:05:23.750 published a famous book one of his really great works called, 01:05:23.750 --> 01:05:26.330 The Interpretation Of Dreams, which 01:05:26.330 --> 01:05:31.850 was the original version in German was published in 1900. 01:05:31.850 --> 01:05:35.310 OK so 113 years ago. 01:05:35.310 --> 01:05:38.860 Now this was an incredibly influential book and also 01:05:38.860 --> 01:05:43.240 central for the emergence of psychoanalysis 01:05:43.240 --> 01:05:51.350 and has been used extensively to interpret quotes why we dream. 01:05:51.350 --> 01:05:55.670 Now the prime, in very summary fashion, 01:05:55.670 --> 01:06:00.260 the prime idea that Freud expressed 01:06:00.260 --> 01:06:09.830 is that dreaming is equivalent to wish-fulling your dreams, 01:06:09.830 --> 01:06:15.110 your wishes, to fulfilling your wishes. 01:06:15.110 --> 01:06:18.320 So that's why it's called wish fulfillment dreams. 01:06:18.320 --> 01:06:24.100 Now, that's interesting because one of the stories he has 01:06:24.100 --> 01:06:26.810 in that book of his, Interpretation Of Dreams, 01:06:26.810 --> 01:06:33.280 is a woman he was psychoanalyzing who one day 01:06:33.280 --> 01:06:38.080 when she came to be, to her session said you know you told 01:06:38.080 --> 01:06:41.710 me the other day that dreams are wish fulfillment's. 01:06:41.710 --> 01:06:46.280 She said, I don't believe that, I had a dream last night 01:06:46.280 --> 01:06:51.610 and it didn't go along with wish fulfillment and Freud said, 01:06:51.610 --> 01:06:54.216 I want you to tell me what the dream was about. 01:06:54.216 --> 01:06:57.510 Well, my dream was that I went to a store 01:06:57.510 --> 01:07:01.930 to buy some food because I was going to have a dinner party 01:07:01.930 --> 01:07:06.890 and when I got to the store it was closed and I could, 01:07:06.890 --> 01:07:08.870 as much as I wanted to I couldn't 01:07:08.870 --> 01:07:10.320 buy the food for the dinner. 01:07:11.740 --> 01:07:15.840 Freud scratched his eyes, you know I'm making that up, 01:07:15.840 --> 01:07:21.730 and he said that's true, he said you know what? 01:07:21.730 --> 01:07:23.370 You didn't want to give a dinner party 01:07:23.370 --> 01:07:25.430 that's why you dreamt that. 01:07:25.430 --> 01:07:29.620 So that's famous psychoanalytic stuff. 01:07:29.620 --> 01:07:31.830 You can always twist things around so 01:07:31.830 --> 01:07:34.760 that it fits with your hypotheses, 01:07:34.760 --> 01:07:39.400 in this case Freud felt that indeed even though she had 01:07:39.400 --> 01:07:42.680 this, what she thought was a contrary dream it was a wish 01:07:42.680 --> 01:07:44.190 fulfillment dream. 01:07:44.190 --> 01:07:46.650 Well that's one part of dreaming, 01:07:46.650 --> 01:07:49.440 what the other part that Freud had emphasized 01:07:49.440 --> 01:07:55.710 is that when we dream so many of our wishes 01:07:55.710 --> 01:07:59.150 are actually unacceptable to ourselves 01:07:59.150 --> 01:08:01.290 and therefore we dream it at night 01:08:01.290 --> 01:08:06.590 and so he constructed in many other studies 01:08:06.590 --> 01:08:11.920 the idea that in humans we have three subdivisions of the mind. 01:08:11.920 --> 01:08:14.660 We have the Id, the ego and the super ego, 01:08:14.660 --> 01:08:16.120 you all know that right? 01:08:16.120 --> 01:08:21.109 So what it means that when you dream at night some 01:08:21.109 --> 01:08:23.370 of the wishes that you, unacceptable 01:08:23.370 --> 01:08:26.240 wishes that aren't in your Id, kind 01:08:26.240 --> 01:08:29.580 of seep through because the super ego 01:08:29.580 --> 01:08:32.965 is not under control since you're asleep. 01:08:34.189 --> 01:08:40.059 So that was his basic idea and of course it 01:08:40.059 --> 01:08:43.979 was then many years later discovered that whenever 01:08:43.979 --> 01:08:48.759 you dream you make all kinds of eye movements. 01:08:48.759 --> 01:08:50.800 You don't make eye movements when you don't dream 01:08:50.800 --> 01:08:52.549 but when you dream you make eye movements. 01:08:53.899 --> 01:08:58.200 Now one of the problems with the Freudian theory 01:08:58.200 --> 01:09:06.380 is that animals also dream and in fact most dramatically, 01:09:06.380 --> 01:09:11.620 animals that hibernate do a lot of dreaming and not 01:09:11.620 --> 01:09:13.740 only dreaming but those animals also 01:09:13.740 --> 01:09:16.029 move their eyes about a lot OK? 01:09:19.200 --> 01:09:25.010 So that observation then kind of shifted 01:09:25.010 --> 01:09:29.069 the notion as to why we have REM sleep 01:09:29.069 --> 01:09:32.800 and so people thought about that and one observation that 01:09:32.800 --> 01:09:37.920 had been made is that when you eliminate a persons 01:09:37.920 --> 01:09:42.899 ability to move the eyes, such as you lose somehow the ability 01:09:42.899 --> 01:09:47.100 to activate your eye muscles, this 01:09:47.100 --> 01:09:48.390 can be done also in monkeys. 01:09:50.109 --> 01:09:56.110 What happens in fairly short order 01:09:56.110 --> 01:10:01.610 is it your eye becomes ill-affected 01:10:01.610 --> 01:10:05.050 and what I mean by that is that the eye loses 01:10:05.050 --> 01:10:07.700 it's perfect roundness to some degree 01:10:07.700 --> 01:10:10.010 and more notably even what happens 01:10:10.010 --> 01:10:13.540 is that your cornea becomes uneven, 01:10:13.540 --> 01:10:17.070 becomes ridged, because you're not moving your eye. 01:10:17.070 --> 01:10:21.920 So that discovery then has led to an alternate theory 01:10:21.920 --> 01:10:25.320 about why we dream which is not nearly as 01:10:25.320 --> 01:10:29.480 romantic or intriguing as Freudian theory, 01:10:29.480 --> 01:10:35.460 namely that we have REM sleep at night in order-- 01:10:35.460 --> 01:10:38.930 and especially have it in animals that hibernate-- 01:10:38.930 --> 01:10:41.920 in order to keep the eyes in healthy condition 01:10:41.920 --> 01:10:47.210 and to keep the cornea nice and smooth and even 01:10:47.210 --> 01:10:50.300 because if you were not to dream at all 01:10:50.300 --> 01:10:52.030 and you would sleep eight or 10 hours. 01:10:52.030 --> 01:10:55.870 Then you would have an uneven, would 01:10:55.870 --> 01:11:02.560 result in having an uneven cornea that 01:11:02.560 --> 01:11:05.420 would make it more difficult for you to see 01:11:05.420 --> 01:11:10.040 and the reason for this then is that animals 01:11:10.040 --> 01:11:13.600 that, which presumably don't have Ids, egos, and super egos 01:11:13.600 --> 01:11:16.900 also dream as do animals that hibernate 01:11:16.900 --> 01:11:22.900 and so there's a necessity to move your eyes while you 01:11:22.900 --> 01:11:25.290 are sleeping or hibernating. 01:11:25.290 --> 01:11:28.200 So that's an alternate theory and we'll 01:11:28.200 --> 01:11:31.420 see one of these years whether they're correct 01:11:31.420 --> 01:11:33.110 but I can tell you, which may not 01:11:33.110 --> 01:11:39.770 be very nice, that basically Freudian theory has taken quite 01:11:39.770 --> 01:11:45.670 a nose dive and in fact today psychoanalysis has become 01:11:45.670 --> 01:11:50.070 largely dead for a number of reasons, 01:11:50.070 --> 01:11:54.140 and so you don't have too many psychiatrists or psychoanalysts 01:11:54.140 --> 01:12:01.620 out there performing those psychoanalytic tasks that they 01:12:01.620 --> 01:12:03.960 had, in which a patient lies down 01:12:03.960 --> 01:12:06.740 on a couch and sort of free associates 01:12:06.740 --> 01:12:13.050 and sometimes even gets hypnotized to talk about some 01:12:13.050 --> 01:12:15.460 of his unconscious wishes and so on. 01:12:15.460 --> 01:12:18.300 So anyway that's the story for today 01:12:18.300 --> 01:12:22.760 and that brings me to an end to eye movement control. 01:12:22.760 --> 01:12:24.430 I hope you'll appreciate the fact 01:12:24.430 --> 01:12:27.660 that even a simple system like eye movements 01:12:27.660 --> 01:12:30.340 is unbelievably complex when it comes 01:12:30.340 --> 01:12:33.270 to the brain controlling it. 01:12:34.460 --> 01:12:37.370 Next time we're going to talk about eye movements 01:12:37.370 --> 01:12:40.390 and towards the end of that I'll come back a little bit 01:12:40.390 --> 01:12:45.862 and talk more about yet another aspect of eye movement control. 01:12:45.862 --> 01:12:47.195 Does anybody have any questions? 01:12:49.550 --> 01:12:50.200 Yes please. 01:12:50.200 --> 01:12:52.444 AUDIENCE: Can you just explain again 01:12:52.444 --> 01:12:55.010 quickly why the bicuculline injection in V1 01:12:55.010 --> 01:12:56.519 causes interference? 01:12:56.519 --> 01:12:58.310 PROFESSOR: OK, that's a very good question. 01:12:58.310 --> 01:13:04.140 Why does bicuculline in the, in V1 cause interference? 01:13:04.140 --> 01:13:09.610 Because it screws up the neurons ability 01:13:09.610 --> 01:13:12.620 to analyze the visual scene. 01:13:12.620 --> 01:13:17.252 You mess up the centers around antagonism, 01:13:17.252 --> 01:13:20.600 you mess up the orientation selectivity of these cells, 01:13:20.600 --> 01:13:22.830 or direction selectivity of them, 01:13:22.830 --> 01:13:26.780 so they're no longer able to analyze the visual scene 01:13:26.780 --> 01:13:27.840 in the normal fashion. 01:13:29.190 --> 01:13:32.670 Yeah that's, and, it certainly you see, 01:13:32.670 --> 01:13:36.070 the V1 is quite far removed really 01:13:36.070 --> 01:13:39.190 from the generation of a motor response. 01:13:39.190 --> 01:13:45.230 If you inject GABA inhibitors into areas 01:13:45.230 --> 01:13:49.500 which are closely linked to the execution of motor acts 01:13:49.500 --> 01:14:00.070 then the, the effect is seen because you generate a motor 01:14:00.070 --> 01:14:03.940 response or if it's muscimol then you inhibit the motor 01:14:03.940 --> 01:14:07.815 response but the frontal, you see this in the frontal eye 01:14:07.815 --> 01:14:10.420 fields but you don't see this in V1 01:14:10.420 --> 01:14:14.240 because V1 is predominantly the system that 01:14:14.240 --> 01:14:18.770 analyzes visual percepts, as are V2 and V4 and all 01:14:18.770 --> 01:14:21.495 those other higher cortical visual areas. 01:14:24.599 --> 01:14:25.515 Any further questions? 01:14:27.170 --> 01:14:30.009 All right very good so I will see you then next Monday 01:14:30.009 --> 01:14:31.425 and I think you'll find that we'll 01:14:31.425 --> 01:14:32.800 have an interesting session. 01:14:32.800 --> 01:14:35.250 We're going talk about movement and we're not going talk 01:14:35.250 --> 01:14:38.010 about regular movement, we're also 01:14:38.010 --> 01:14:44.820 going to talk about confusing kinds of movements, 01:14:44.820 --> 01:14:47.460 like especially very important apparent motion. 01:14:48.700 --> 01:14:51.810 You realize and just to say one more word here, 01:14:51.810 --> 01:14:59.970 that nowadays when you go home and watch television almost all 01:14:59.970 --> 01:15:02.580 the motion that you see on the TV 01:15:02.580 --> 01:15:06.150 is apparent motion, not real motion 01:15:06.150 --> 01:15:07.575 and I-- keep thinking about that-- 01:15:07.575 --> 01:15:09.200 and I'll tell you about that next time. 01:15:11.575 --> 01:15:13.967 AUDIENCE: Monday is actually a Holiday. 01:15:13.967 --> 01:15:14.800 PROFESSOR: Oh, yeah. 01:15:14.800 --> 01:15:15.800 Sorry it's not Monday. 01:15:15.800 --> 01:15:19.840 It's our next session is next Wednesday. 01:15:19.840 --> 01:15:21.390 Sorry about that.