Auditory Physiology

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Auditory Physiology

• Chapter 11
• Linda McCoy

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Outer Ear Function

• Collect sound

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Middle Ear Function

• Increase the pressure arriving at the cochlea
• Resistance to flow of energy is impedance
• Net gain of approx 30 db

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Inner Ear

• Vestibular mechanism
• Input to the proprioceptive system
• The sense of one body in space
• Auditory mechanism
• Spectral and temporal acoustic analysis
• Traveling wave along the basilar membrane

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• The traveling wave always travels from base to
  apex
• Cilia of outer hair cells are embedded with the
  tectorial membrane
• As the traveling wave moves along the basilar
  membrane, the hair cells are displace relative to
  the tectorial membrane.
• This motion produces a shearing action.

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• The inner hair cells are not embedded in the
  tectorial membrane but are moved by the fluid
  movement of the endolymph.
• At less that 40 dB, the outer hair cells are
  important in coding intensity and the inner hair
  cells are essential in frequency coding.

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Tonotopic Arrangement/Array
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• Electrical events
• Read to you by Jessica S.
• See page 474

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Neural Responses

• Two types of VIII neurons
• Low spontaneous rate
• High spontaneous rate
• The characteristic or best frequency of a neuron
  is the frequency to which it best responds.
• The tonotopic array is relayed to the auditory
  system by individual nerve fiber activation.

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Auditory Pathway
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• Cochlear Nucleus (CN)
• Superior Olivary Complex (COS)
• Inferior Colliclus (IC)
• Medial Geniculate Body (relay of Thalamus)
• Ventral MGB projects directly to primary auditory
  reception area
• Medial portion projects to of the regions in
  temporal lobe
• Dorsal portion projects information to the
  association regions of the cerebrum

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Cerebral Cortex
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