Transcript Audition Outline - Villanova University

Audition Outline
•
Perceptual dimensions
• Ear Anatomy
• Auditory transduction
• Pitch Perception
– by Place Coding
– by Rate coding
•
Sound Localization
– by phase difference
– by intensity difference
Perceptual Dimensions
Stimulus
Vision
Audition
Frequency
Hue (nm)
(‘color’)
Brightness
Pitch (Hz)
Amplitude
Purity (vs.
complexity)
(e.g. 440Hz)
Loudness (dB)
Saturation
Timbre
complexity
Sound:
Variation of pressure over time
Ear Anatomy
Air
Bones
Liquid
Eardrum >> oval window
Transduction
of sound
-
Basilar membrane oscillates
Hair cell cilia bends
Cations inflow
Depolarization
Increased firing rate
• Bend on opposite direction
• Reduced firing rate
Pitch Perception:
Place vs. Rate Coding
Hz
0
20
Volley Code
language 500
HUMAN
RANGE
2000
Place Code
4000
apex
Pitch Perception: Rate code (Volley)
• E.g. 100 Hz tone (100 cycles
per sec) -> 100 spikes/sec,
• Used for lower
frequency sounds
<1500 Hz).
Pitch perception:
Place coding
• The cochlea has a
tonotopic organization
• For high frequencies
Sound Localization
Interaural Intensity Difference
(high frequency)
Interaural Time Difference
(low frequency)
Delay Lines –
Interaural Time
Difference (ITD)
Deafness
• Conduction deafness
– outer or middle ear deficit
– E.g. fused ossicles. No nerve damage
• Sensorineural
– Genetic, infections, loud noises (guns & roses),
toxins (e.g. streptomicin)
– Cochlear implants
• Central
– E.g. strokes
• Primary Auditory cortex:
– Tonotopic Organization
– Columnar Organization
– Cells with preferred
frequency, and
– cells with preferred interaural time difference
Spare slides
Auditory Nerve Tuning Curves
(receptive fields)