Dear Matt,
Your reference to Cariani's research into temporal properties of
hearing reminded me of another observation he had made concerning
the substantial effect phase associated with the complex stimulus
had on the statistics of the ISI with the peaks being less
pronounced than for a pure tone. I am not sure if there has ever
been much discussion about phase in this forum, and have always
wondered as to how the rest of this illustrious group understands
this result.
IMHO I do agree with you that a feedback must be taking place if for
nothing else than to account for phase even for a pure tone
stimulus, which is why implementing source location in binaural
experiments is so difficult. Get rid of the phase and the problem
becomes much easier.
Thanks for bringing this up now as it does explain, to me at least,
why the BM oscillates in that peculiar way and contrary to all
explanatory models that have been offered for review. Regards,
Randy Randhawa
On 12/3/2012 11:46 AM, Matt Flax wrote:
Hi Bob,
There are studies which suggest that place and pitch are far
from synonymous.
Consider Zheng's research and the references therein clearly
demonstrate pitch reorganisation in rodents :
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3438459/
Also Cariani's research into temporal properties of hearing, in
papers from '96 to 2001 and more... suggest that in certain
frequency ranges time codes dominate!
Further, the alive and dead Cochlea exhibits large frequency
shifts at the same place w.r.t. each other ... consequently it
could be assumed that the neural control (efferent control) is
very important for tuning our peripheral hearing circuit ... in
my opinion, temporal control is working in conjunction with
place effects... hard to think of them operating in isolation.
In the hypothesised mixed mode cochlear amplifier, the degree of
feedback is critical to the tuning properties of each Cochlear
segment.
http://adsabs.harvard.edu/abs/2011AIPC.1403..611F
In a dead mouse ear, with no feedback, there is roughly a .25
octave shift (from memory) w.r.t. a healthy ear.
Matt
On 12/02/2012 07:47 AM, Bob Masta wrote:
Can someone explain the supposed mechanism behind neural
timing and pitch shift? I don't understand what is being
proposed. As I undestand it, since pitch is encoded as
*place* along the BM, the neurons respond with a firing
rate that encodes *loudness* for their particular frequency
place. The firing rate does not encode the frequency of
the sound itself.
What am I missing here?
Best regards,
Bob Masta
=============
On 1 Dec 2012 at 9:50, Pierre Divenyi wrote:
Hi Oded,
Your three-step reasoning makes sense but, indeed, it should be
experimentally verified. As to the age-related change of neural
oscillations, Art Wingfield believes that the brain "slows down" as we get
older. Such a slowing-down could also explain the upward AP shift because
our reference would shift downward. How this central effect squares with the
peripheral, BM-stiffening effect is unknown but, again, could be studied in
the lab.
-Pierre
On 12/1/12 5:17 AM, "Oded Ghitza" <oghitza@xxxxxx> wrote:
Hi Pierre,
If (1) you accept Julius's model of pitch perception, (2) interpret -- as he
did -- the central component of the model as a mechanism that adjusts f0 of
an internal harmonic sieve to the point where the MMSE between the sieve and
the input pattern is minimum, and (3) assume that such mechanism is realized
by a neuronal circuitry with oscillations ("rhythms") at the core (maybe
related to Langer, in the late 80's and in the context of pitch perception,
who measured "temporal rings" in chicks); then, a possible way to examine
the phenomenon (whether perceived pitch should go up or down, in
particular), is to look at how the frequency range of neuronal oscillations
change with age.
--
Oded.
Bob Masta
D A Q A R T A
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