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Re: Questioning the volley principle
Dear Matt and List,
Its seems to be suggested that frequency is simply encoded via the
synchronization of the incoming freqeuncy and the frequency of the neural
firing rate. This is likely true, however, it only holds up to about 4000Hz.
After which I beleive the higher freqeuncies are assumed to be encoded
dependent on their "Place" in the cochlea. As Von Bekesy, and many other after
him demonstarted, the cochlea acts as a series of band-pass filters wherein
higher freqeuncies are encoded in the basal region of the cochlea, and lower
freqeuncices in the apex.
I am not sure if I have answered your question on the Volley Theory, rather I
am just giving you my understanding of how frequency is encoded in the cochlea.
Oh, one last thing, I am not sure how you think about amplitude encoding, but I
beleive it has been evidenced by Liberman (1978) that level is encoded
depending on the response of the different spontatnous rate afferent fibers.
High spontatous rate fibers respsond to low level stimuli, whereas low
spontanous fibers repsonsd to high level stimul. And considering that the low
spont. fibers have a dynamic range of +40dB, that allows for the system to
respsond up to +100dB!
Quoting Matt Flax <flatmax@IEEE.ORG>:
> I am not sure I see the need for the volley principal.
> If the neurally transduced basilar/organ of the Corti signals are
> frequency specific, then surely a neural impulse cognitively implies a
> frequency ?
> It is also known that neural firing rate (in afferents) is largely
> determined by SPL or intensity. So a combination of frequency
> selectivity (neuron selection) and firing rate determine sound frequency
> and intensity.
> Does anyone agree ?
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