Hearing Loss and Central Auditory Processing

59 Primary Auditory Cortex

Learning Objectives

Know where Heschl’s gyrus is.

Be able to describe what tonotopic maps in A1 are.

Heschl’s gyrus is a part of the temporal lobe, and the primary auditory cortex (A1) is located on it, in the superior temporal cortex. The A1 contains tonotopic maps. The word “tonotopic” means that neurons that respond to similar frequencies are close to each other in the cortex. On a fine scale, this is like orientation pinwheels. Retinotopy, the mapping of visual input from the retina to neurons, is an example of this on a more coarse scale. Tonotopic maps can shift with experience. For example, monkeys who get really good at discrimination sounds in a particular frequency band grow fatter cortical representations of that frequency. Additionally, experienced musicians tend to have elaborated A1 maps.

The primary auditory cortex is highlighted in the temporal lob of the brain.
Fig. 6.11.1. The primary auditory cortex (PAC) is found on the posterior superior temporal gyrus and portions of the planum temporale and Heschl’s gyrus. The PAC is located in Broadmann areas 41 and 42. (Provided by: OpenStax. License: CC-BY 4.0)

It is important to note that we don’t simply perceive the tones represented in the A1. For example, we perceive the missing fundamental in a series of harmonic tones. The A1 is necessary for pitch perception, but not duration information. Furthermore, it is not sufficient for pitch perception, as damage in the inferior temporal cortex affects our ability to identify tones. The A1 is surrounded by a region of cortex called the Belt area. Neurons in the belt area respond to the combinations of frequency and details of timing that define more complex characteristics of sound.

 

This image highlights that there is a primary auditory cortex on both the left and right hemispheres.
Fig.6.11.2. This figure shows a schematic representation of the tonotopic organization of the auditory cortices of both the left and right hemispheres. Low frequencies (500 HZ) are represented laterally or closer to the surface of the cortex and high frequencies represented medially or closer to the center of the brain. (Provided by: OpenStax. License: CC-BY 4.0)

 

Here is a video that provides an additional overview on tonotopy!

 

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Cheryl Olman PSY 3031 Detailed Outline
Provided by: University of Minnesota
Download for free at http://vision.psych.umn.edu/users/caolman/courses/PSY3031/
License of original source: CC Attribution 4.0
Adapted by: Maida Fazlic

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Introduction to Sensation and Perception by Students of PSY 3031 and Edited by Dr. Cheryl Olman is licensed under a Creative Commons Attribution 4.0 International License, except where otherwise noted.

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