Memory II: Amnesia and Memory Systems

Session Overview

What conditions can impair your memory? How is your memory affected by these impairments? In this lecture, we will study amnesia, how it can influence our memory systems and how amnesia patients have helped us pinpoint areas in the brain crucial to memory. A particular highlight of this session is Prof. Gabrieli’s stories of working as a graduate student directly the famous amnesiac patient H. M.

Keywords: memory systems, amnesia, anterograde amnesia, retrograde amnesia, hippocampus, Huntington’s disease, patient H.M., declarative memory, procedural memory

Cartoon of someone who has just been ‘amnesiacked.’ (Image by MIT OpenCourseWare).

Session Activities

Readings

Read the following before watching the lecture video.

[Sacks] Chapter 2 “The Lost Mariner” (pp. 23-42)
Finish the chapter you started for the previous session:
- [K&R] Chapter 5, “The Biology of Mind and Behavior: The Brain in Action.”
  - Study outline for K&R Chapter 5 (PDF)
- [Stangor] Chapter 8, “Remembering and Judging”

Lecture Videos

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Lecture 11: Memory II: Amnesia and Memory Systems

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The Importance of Memory

Anterograde Amnesia: Patient H.M. and the Role of the Hippocampus in Memory Formation

Types of Memory and Q&A about Patient H. M.

Retrograde Amnesia

Neural Memory Systems and the Effect of Huntington’s and Alzheimer’s Diseases on Memory

Video Resources

Removed Clips

Lecture Slides (PDF - 2.0MB)

Discussion: Memory

So, if the essential task of a memory system is to carry information forward in time, what properties should that system have? Think about the memory devices you use in everyday life: A USB stick, a post-it note, your mind, etc. What do they need to be able to do?… Read more »

Check Yourself

Name, describe and give examples of the two types of explicit memory and the three types of implicit memory.

› View/hide answer

The three types of explicit memory are semantic memory and episodic memory. Semantic memory is our facts and general knowledge about the world. The three types of implicit memory are procedural memory, priming, and learning through conditioning. Procedural memory consists of or motor and cognitive skills, or know how to do certain things. Priming is enhanced identification of objects and words, or changes in behavor as a result of recent experiences. Learning through conditioning is learning to expect rewards or punishment under certain conditions.

Examples of each type of memory:

Semantic: The sky is blue, dogs have fur, Africa is below Europe.

Explicit Memory: What you had for breakfast, your first date, what you did for your birthday.

Procedural: How to hit a baseball, how to do simple arithmetic, how to start your car.

Priming: Seeing a river and someone says they are going to the bank. Priming will make it more likely for you to think they are going to the bank of a river or stream rather than a bank to withdraw money.

Learning through conditioning: After several years in elementary school you learn to associate a good report card with the expectation of a reward, such as cookies or a new toy from your parents.

Further Study

These optional resources are provided for students that wish to explore this topic more fully.

TYPE	CONTENT	CONTEXT
Supplemental reading	Sacks, Oliver. “The Abyss: Music and Amnesia.” The New Yorker, 2007.	An article by Oliver Sacks about an individual with retrograde amnesia and his wife.
Blog post	Neurophilosophy blogger. “Amnesia in the movies.” Scienceblogs.com, 2009.	Prof. Gabrieli talks about how inaccurate most portrayals of amnesia in popular media are; this article gives some examples of movies that get it right.

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Session Overview

How do we carry information forward in time? This discussion session complements the prior lecture sessions Memory I and Memory II.

Demonstration

Before jumping into the discussion of topics related to memory, try this brief demonstration. Here’s what to do: Click the link below, spend exactly 15 seconds looking at the faces that pop up, and then click the link again to hide the image. Then continue on with this discussion on this page. We’ll check back with you in a bit…

› View/Hide Image

Discussion

What is memory for? What does it do for us? The classic example of the importance of memory is touching a hot stove. The first time you touch a hot stove you realize it was a bad deal. You store that away for the future, so if you see a stove again, you don’t touch it. So, memory guides our future behavior based on our past experiences, ideally to increase our chances of survival.

› Sample Answer

It should record what’s going on now (encoding).

It should retain the information (storage).

It should provide access at a later time (retrieval).

There are several different types of memory systems in the brain which accomplish this task of carrying information forward in time in very different ways. The terms used by psychologists include sensory memory, short-term memory, and long-term memory, and each of these terms have been refined by neuroscience research. We’ll talk in lecture about, for example, the degree to which certain kinds of memory are hippocampus-dependent, and about how encoding, storage, and retrieval are accomplished in these types of memory.

A good example of sensory memory would be if I showed you a bunch of letters just for a second and asked you to report as many of them as you could.

Most people can report the first four or five, and it seems like they just can’t take in any more information so quickly. But a carefully-designed experiment can show that sensory memory has much more capacity than you’d think. In one study, the same letters were flashed, but a high-, medium-, or low-pitched tone was played immediately after, indicating which of the three rows to report. As it turns out, you can report any of the rows with pretty good accuracy. The idea is that our sensory memory is very good. It can store a lot of information, but it fades very rapidly. The transmission of information from sensory memory to short-term memory (which enables you to say the names of the letters) is constrained. You just can’t say all of the letters you saw before that sensory memory decays.

Short-term memory is the kind of memory that requires active maintenance, like looking up a phone number and repeating it to yourself until you can dial it. It’s transient, it requires maintenance, and it only lasts a couple of seconds. Long-term memory, though, brings us to the topic of forgetting, and to Ebbinghaus, who invented and memorized word lists. On the first day he’d remember most of them; on the second day, not as many; on the third day, not as many; and so on and so on. And he discovered this power law relationship (the “forgetting curve”) between what you need to know and how much time has elapsed, which seems to be an intrinsic property of human memory.

Image by MIT OpenCourseWare.

Critical Thinking

The graph below depicts the results of an experiment in which participants had to remember 15 items. Take a look at the graph and describe the results for both the 0-second delay condition and the 30-second delay condition.

Based on what you know about memory processes, explain the results for the first three items presented and the last three items presented.

› Sample Answer

If you’re prompted to recall items in a list immediately after learning it, you often remember the last few items. However, if you wait 30 seconds, you probably won’t remember the last few items. Regardless of the delay period, the first few items are, on average, recalled most accurately.

We remember earlier items better because we have more time to put them into long-term memory, a phenomenon known as the primacy effect. In addition, the items seen more recently are also remembered better because they are still in short-term memory — this is the recency effect.

If you’ve been rehearsing the items, the first few have had the opportunity to enter long-term memory, where they persist, even after a 30-second delay.

Discussion

Another way to classify memory is by whether it’s implicit or explicit. Explicit memory is stuff that we could recall if we were asked to recall it, whereas implicit memory is stuff that you do without any active representation or self-description. Implicit memory includes habits (stepping on the brake when you see a red light), skills (riding a bike), priming, and classical conditioning.

Now might be a good time to review the difference between classical conditioning and operant conditioning. (Return to Discussion: Learning if you need a refresher.) Why is classical conditioning considered implicit memory, while operant conditioning is explicit?

Demonstration: Implicit Memory

Listen as Tyler introduces the demonstration: (MP3) (0:00:40)

Then click to reveal a game.

› Play the Game

Having just listened to Tyler’s story, here are some word stems. What words first come to mind?

CAR ___
MET ___
PRO ___
PER ___
THI ___
POT ___
_HA_R__N
A__A__IN

After you’ve played the game, listen to Tyler’s explanation: (MP3) (0:03:12)

› Spoiler (what you heard first)

The chairman of the committee usually opens the meeting with one of his boring and sometimes even perverse lectures. Today he started with some stupid proverb: I can’t even remember it – something about not planting thistle seeds. Then he went on a pointless tangent about how to guard a political leader from a potential assassination in a crowded place such as a carnival. Is there any method behind the madness of his talks?

Demonstration: Explicit Memory

Remember those faces that you saw at the beginning of the discussion? Let’s test your memory. Click the link below and try to determine which of these men you’ve seen before.

› View/Hide the Test

How did you do?

› View/Hide the Answer

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Removed Clip 1: Patient H.M.’s Brain Being Prepared For Study

Video of patient H.M.’s brain being sliced into histological sections. The Brain Observatory, Department of Radiology at UC San Diego. December 2, 2009.

Removed Clip 2: Living with Amnesia

Excerpt (initial 5 minutes) from “Living With Amnesia: The Hippocampus and Memory.” Episode 18 in The Brain. Annenberg Learner / Colorado State University, 1997. [Scroll down to Episode 18 and click on the “VoD” box]

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Introduction to Psychology