Transcript Document

Psychology 304: Brain and Behaviour
Lecture 24
1
The Auditory System and the Vestibular 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?
4. What is the neurological basis of deafness?
5. What are the biological mechanisms associated with
vestibular perception?
2
What is the structure of the ear and where are the
receptors for sound? (continued)
The Structure of the Ear
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InnerInner
Hair
Cells
and Outer Hair Cells
Outer Hair
Cells
Inner Hair
Cells
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Auditory nerve
Outer Hair Cell Contact with
the Tectorial Membrane
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• High frequencies stimulate hair cells close to the oval
and round windows. Low frequencies stimulate hair cells
at the tip of the cochlea.
• 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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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; the
posterior auditory pathway is thought to be involved in
locating sounds.
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Pathways to Auditory Association Cortex
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What is the neurological basis of deafness?
• Although impaired hearing is a common human disability,
complete deafness is rare.
• There are three common classes of hearing impairments:
conductive deafness (outer or middle ear damage),
sensorineural deafness (inner ear damage), and central
deafness (cortical damage).
• Cochlear implants can improve the hearing of those who
have sensorineural deafness.
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Cochlear Implant
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Cochlear Implant
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What are the biological mechanisms associated with
vestibular perception?
• The functions of the vestibular system include the
detection of head movement, balance, and the
maintenance of the head in an upright position.
• The vestibular system has two components: the
semicircular canals and the vestibular sacs.
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Vestibular Sacs and Semicircular Canals
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• Vestibular receptors are found in enlargements on the
semicircular canals called ampullae. These receptors
respond to angular (i.e., rotational) acceleration of the
head.
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Receptor Cells in the Semicircular Canals
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The Auditory System and the Vestibular 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?
4. What is the neurological basis of deafness?
5. What are the biological mechanisms associated with
vestibular perception?
20