Download The Auditory System

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 ….
Functions of the:
(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.”
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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.
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The Receptors for Sound
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Cochlea Slice
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Cilia of Inner Hair Cells
Cilia of Outer Hair Cells
Hair Cells Images
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InnerInner
Hair
Cells
and Outer Hair Cells
Outer Hair
Cells
Inner Hair
Cells
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Auditory nerve
Hair Cell Contact with
the Tectorial Membrane
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Tip Links
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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).
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Tonotopic Organization
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• The vibrations of the cochlear fluid are ultimately
dissipated by the round window.
• When hair cells are stimulated, action potentials are
triggered that pass down axons of the auditory nerve—a
branch of cranial nerve VIII.
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The 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.
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Pathways 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.
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Auditory 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”).
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Pathways 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?
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