Lecture 8 Flashcards
(11 cards)
auditory nerve anatomical arrangement
high frequency fibres located on outside
low frequency fibres located in the middle
what type of neuron encodes sound information
Type I
auditory nerve spontaneous activity
there is activity in regions of the auditory nerve that are not being maximally displaced or even in the absence of sound
parameters that contribute to pitch perception (frequency coding)
- Place of stimulation (place code, passive)
- OHC contribution (active)
- Temporal code (phase locking)
tuning curves along the cochlea
base –> sharp tuning curves (high freq)
apex –> broad and wide tuning curves (low freq)
Is temporal code/phase locking more important in the base or the apex
APEX: low frequencies phase lock well
what is the origin of phase locking
the hair cell, the receptor potential
phase locking in low vs high frequency
low: action potential fires at the same angle of sound pressure wave, phase locks well
high: sound pressure waves are much narrower, so AP firing occurs at different angles of the sinusoidal wave, some but maximum 30% phase locked
intensity coding: the three neural parameters coding loudness
Number of neurons firing (louder it is the more neurones fire)
Rate of Neural firing (louder, higher firing)
Threshold of neurons firing (Type I)
intensity coding: threshold of type I auditory nerve fibres variation
Low S/R
- high threshold (fire with high intensity sound)
- located modiolar side of IHC
- smaller synapse wth IHC
High S/R
- low threshold (fire in low intensity sound)
- located pillar side of IHC
- larger synapse with IHC
S/R = spontaneous rate
Which threshold Type I neurons normally lost first
low S/R –> they discriminate sound in noise, think cocktail effect