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Psychology 304: Brain and Behaviour

Lecture 27

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Announcement

Please note that course evaluations are available online. If you have not received an e-mail directing you to the evaluations for this course, you may provide your evaluation at: https://eval.olt.ubc.ca/arts.

Course evaluations will be available until December 5th.

Your feedback is extremely valuable—both to the Psychology Department and to me.

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From last class ….

(a) primary somatosensory cortex (SI): Contralateral processing.

(b) secondary somatosensory cortex (SII): Bilateral processing.

(d) somatosensory association cortex (posterior parietal lobe): Vision and touch, as illustrated by “asomatognosia.”

Functions of the:

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The Auditory System

1. What is the structure of the ear and where are the receptors for sound? (continued)

2. How is information about sound relayed to the brain?

3. What are the major areas of the brain that are associated with the perception of sound?

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By the end of today’s class, you should be able to:

1. describe the structural and functional features of the outer, middle, and inner ear.

2. explain how an action potential is generated in the afferent nerve fibres of the auditory system.

3. review the pathway by which auditory information is transmitted from receptors to the brain.

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4. identify the locations and functions of the primary cortex, secondary cortex, and association areas for the auditory system.

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What is the structure of the ear and where are the receptors for sound? (continued)

• The organ of Corti contains the receptors for sound.

8The Receptors for Sound

9Cochlea Slice

10 Hair Cells Images

Cilia of Outer Hair CellsCilia of Inner Hair Cells

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Inner Hair Cells

Inner Hair Cells

Outer Hair Cells

Inner and Outer Hair Cells

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Hair Cell Contact withthe Tectorial Membrane

Auditory nerve

13Tip Links13

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• Place theory and volley theory have been proposed to explain the how sound receptors facilitate the perception of pitch.

• Tonotopic organization is found at all levels of the auditory system (e.g., cochlea, inferior colliculi, auditory cortical regions).

15Tonotopic Organization

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• When hair cells are stimulated, action potentials are triggered that pass down axons of the auditory nerve—a branch of cranial nerve VIII.

• The vibrations of the cochlear fluid are ultimately dissipated by the round window.

17The Structure of the Ear

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How is information about sound relayed to the brain?

• Sound information is relayed to the brain via a network of auditory pathways.

19Pathways of the Auditory System

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What are the major areas of the brain that are associated with the perception of sound?

• The majority of thalamic neurons that receive sound information subsequently project the information to the

primary auditory cortex. Thereafter, information is projected to the secondary auditory cortex (SII) and association areas.

21Auditory Areas of the Brain

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• Current theory suggests two large areas of auditory association cortex: the prefrontal cortex and the posterior parietal cortex.

• The anterior auditory pathway leading to the prefrontal cortex is thought to be involved in identifying sounds (“what”); the posterior auditory pathway is thought to be involved in locating sounds (“where”).

23Pathways to Auditory Association Cortex

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The Auditory System

1. What is the structure of the ear and where are the receptors for sound? (continued)

2. How is information about sound relayed to the brain?

3. What are the major areas of the brain that are associated with the perception of sound?