HST.723J | Spring 2005 | Graduate

Neural Coding and Perception of Sound


Theme 1: Masking and Frequency Selectivity

Lab 1: What was the stimulus? (PDF)

The purpose of this laboratory exercise is to illustrate how sound stimuli are coded in the temporal discharge patterns of auditory-nerve fibers. The auditory nerve is a good starting point for understanding neural coding of acoustic stimuli because responses are stable, well-characterized, and relatively easy to interpret in terms of cochlear mechanisms. The techniques you will be using in this lab are also applicable to neurons in the central auditory system and other sensory systems. One limitation of this exercise if that only techniques for analyzing response of single neurons are considered. A different set of techniques deals with how information is coded in networks of interconnected neurons.

Lab 2: Fundamentals of perceptual audio encoding (PDF)

Lab 2 Notes (PDF)

Lab 2 materials courtesy of Craig Lewiston. Used with permission.

No aspect of auditory psychophysics is more relevant to the design of perceptual auditory coders than masking, since the basic objective of perceptual audio coders is to use the masking properties of sounds to hide quantization noise.

In the spirit of MIT’s motto, Mens et Manus or learn by doing, this lab allows you the opportunity to carry out some psychophysical measurements on yourselves and gain some “ear-on” experience with auditory masking. The experiments should be carried out in pairs, so you can take turns running the experiments.

Theme 2: Cellular Mechanisms in the Cochlear Nucleus

Lab 3: Single-unit typing in the cochlear nucleus (PDF)

In this laboratory, you will classify single units recorded from the cochlear nucleus on the basis of their PST and interspike interval histogram shapes. The data was recorded from an anesthetized preparation in an experiment performed by Dr. Peter Cariani. You will be provided with a tape recording of spikes and a computer program that enables you to construct the histograms. You will work in groups for the lab, but please write separate write-ups of your results. For your lab write-up, please limit the text to 4 pages (excluding figures).

Theme 3: Binaural Interactions

Lab 4: Neuroanatomy demonstrations (PDF)

This brief introduction to the neuroanatomy demo describes the main types of stains used in for revealing different anatomical features of neurons, and how the different types of cochlear nucleus neurons appear under these stains.

Lab 5: Compartmental model of binaural coincidence detector neuron (PDF)

The purpose of this laboratory exercise is to give you hands-on experience with a compartmental model of a neuron. Compartmental models differ from point neuron models such as the Kalluri and Delgutte (2003) model studied in the Cochlear Nucleus theme in that they explicitly represent the geometry of the neuron. In a point neuron, all points inside the cell are assumed to have the same electrical potential. This assumption is appropriate for neurons that are “electrically small”, i.e. small relative to their length constant. For neurons with long, thin dendrites, the point neuron assumption is inappropriate, and one must use a compartment model. In this type of model, the neuron’s volume is divided into separate compartments, each with its own potential. Typically, there could be separate compartments for the cell body, the axon hillock, and several compartments for the axon and each of the dendrites. The potential at each point is determined by the distribution of both active and passive membrane conductances as well as the intrinsic resistance of the intracellular material. Obviously, compartment models can be computationally much more demanding than point neurons.