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Re: Place-based pitch

It seems to me that we have the same problem with place-base pitch and
with temporal pitch if we believe that at least the initial mechanisms
for temporal pitch are monaural. In the place mechanism, some sort of
central processor must ultimately associate a pitch with a particular
inner hair cell or group of nearby inner hair cells and in the temporal
models it would have to associate a pitch value with a "pitch" neuron or
group of neurons (possibly located in the inferior colliculus). In either
case, the "tuning" properties of the inner hair cell or "pitch" neuron
will depend on a host of anatomical and physiological parameters that
would not be expected to be indentical on the two sides.

To me the wonder is how, it is that most of us have a pretty good match
between the left and right ears when it comes to pitch and other salient
perceptual qualities. Clearly, there must be some sort of mechanism (call
it learning or plasticity) in the central nervous system that compensates
for biophysical differences between the left and right ears and
their assocated neural pathways. Further more these mechanisms appear to
do a reasonable job of dealing with aging ears and aging brains.


David C. Mountain, Ph.D.
Professor of Biomedical Engineering

Boston University
44 Cummington St.
Boston, MA 02215

Email:   dcm@bu.edu
Website: http://earlab.bu.edu/external/dcm/
Phone:   (617) 353-4343
FAX:     (617) 353-6766
Office:  ERB 413
On Wed, 24 Mar 2004, Al Bregman wrote:

> Dear list,
> There is a phenomenon that suggests a contribution of place information to
> pitch at all frequencies: the phenomenon of diplacusis, the hearing of
> different pitches for the same sound at the two ears (when presented to only
> one ear at a time).  It is hard to imagine how a temporal mechanism could
> produce such an effect, but if the two cochleas were slightly different
> anatomically, one could see how this phenomenon could occur.  The idea is
> that place plays a secondary role at all frequencies, perhaps choosing
> between temporal conclusions that are close to one another in probability
> based on the temporal mechanism (e.g., octave differences), but can
> influence the pitches to be slightly "off" when the two cochleas have
> different topologies.
> Al
> -----------------------------------------------------------
> Albert S. Bregman, Emeritus Professor
> Dept. of Psychology, McGill University
> 1205 Docteur Penfield Ave.
> Montreal, QC  Canada  H3A 1B1
> Office Tel: (514) 398-6103, Fax -4896
> E-mail: al.bregman@mcgill.ca
> -----------------------------------------------------------