Auditory Physiology and Hearing

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PSY 3520 Sensation and Perception
Auditory Physiology and Hearing
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Auditory Physiology HearingLecture Outline

• I. The Stimulus for Hearing
• A. Pure Tones
• 1. Amplitude
• 2. Frequency
• B. Perceptual Dimensions of Sound
• C. Complex Sounds and Fourier Analysis
• II. Structure and Functioning of the Auditory
  System
• A. Outer Ear
• 1. Pinnae
• 2. Auditory Canal (External Auditory Meatus)
• 3. Tympanic Membrane (Eardrum)
• B. Middle Ear
• 1. Ossicles (Malleus/Hammer, Incus/Anvil,
  Stapes/Stirrup)
• 2. Function of the Ossicles
• 3. Eustachian Tube
• C. Inner Ear
• 1. Cochlear Compartments
• 2. Organ of Corti
• 3. Transduction What causes a hair cell to
  bend?

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Auditory Physiology HearingLecture Outline

• III. The Code for Frequency
• A. Place Code
• B. Frequency (Timing) Code
• C. Pitch and Loudness Perception Place vs.
  Frequency Theory
• IV. Place and Timing Information in the Central
  Auditory System
• A. Auditory Pathways
• B. Place Information
• C. Timing Information
• V. Physiology of Sound Localization
• A. Interaural Time Difference
• B. Interaural Intensity
• VI. The Audibility Curve

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Inner Ear

• Main structure of the inner ear is the
  _______________

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Cochlea

• Three compartments
• _________________________
• _________________________
• _________________________
• Cochlear duct
• formed by 2 membranes
• _____________________
• _____________________

• cochlea functioning

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Organ of Corti

• The primary auditory receptor structure (15,000
  hair cells)

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Transduction

• Transduction occurs in the ____________ housed in
  the _______________
• What causes stereocilia of a hair cell to bend?
• Footplate of the stapes pushes the oval window
• Causes motion in the cochlear fluid
• Tectorial membrane

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Hair Cells

• There are two types of hair cells
• _____________
• _____________

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Hair Cells
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Auditory Nerve Fibers
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Review

• Auditory Perceptual Process

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The Code for Frequency

• Two major theories
• ________________
• _________________

Bekesy
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Place Code Theory

• Georg von Bekesy (1920s) vibration of the
  basilar membrane

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Place Code Theory

• Bekesy (1960s) properties of the envelope of
  the traveling wave
• Envelope is peaked at ____ point on the basilar
  membrane
• Position of the peak is a function of the
  ________ of sound

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Place Code Theory

• Further support
• Culler et al. (1943) cochlear responses
• Russell Sellick (1977) hair cell tuning
• Kiang (1975) auditory nerve fiber tuning

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Timing Code for Frequency/Frequency Theory

• Rutherford (1886) neural firing rate
• Wever (1949) volley principle
• Rose et al. (1967) phase locking
• _____________ neurons fire in synchrony with
  the phase of a stimulus

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Pitch Perception

• Periodicity Pitch the missing fundamental

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Physiological Aspects of Loudness

• How can nerve firing signal loudness?
• When intensity increases
• Neurons already firing saturate (above 40-50 dB
  SPL)
• Neurons at other places on basilar membrane begin
  to fire more rapidly (pattern of auditory firing
  becomes broader)

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Central Auditory System
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Place Information

• Place information is maintained through ________
  mapping
• Auditory cortex has
• ________ organization
• Place code mainly
• responsible for pitch
• perception

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Timing Information

• Phase locking not maintained as move up through
  the auditory pathway
• When phase locking occurs it is for frequencies
  below ________ Hz
• Timing mechanism provides information about _____
  frequency sounds

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Physiology of Sound Localization

• ______________
• Interaural time difference detector
• ______________
• Neurons responding to certain locations in space
• Knudsen Konishi (178)

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Audibility Curve