Re: Discussion about "place pitch" concept

[Martin Braun <nombraun@xxxxxxxxx>]

On Thursday, March 18, 2004 6:49 PM, Uwe Baumann wrote:

> There have been discussions about the reasons of the poor contribution of
> temporal information to pitch perception in electrical hearing. Poor
neural
> survival  is one major argument. But even in case of a reduced number of
> fibers, the rate code will be transmitted more accurately in electrical
> hearing than by normal acoustical stimulation (Hartmann, 1984).

Because this is an accuracy that is enforced rather "brutally". The price of
the "brutality" is the low limit of neural phase coupling. More important
than reduced numbers of afferent fibers in the cochlea probably is the
absence of inner hair cells and their afferent synapses. Both are extremely
sophisticated machines, which we only have started to explore. The secrets
of HF period coding are hidden here.


> The outlined observations are not able to counter the notion "There is no
> physiology of place pitch", but they clearly indicate that there is a
place
> pitch in psychophysical electrical stimulation of the cochlea by means of
> intracochlear electrode arrays.

Thanks, Uwe. This is an important point. For peripheral encoding of period
information the place of encoding is important, also in normal hearing. But
this is not what theories of "place pitch" were dealing with. Rather, they
suggested a coding of pitch by central cochleotopic patterns of harmonics,
for which physiological evidence could never be found.

By the way, there is a very recent and highly interesting paper which
demonstrates the importance of peripheral encoding place: Oxenham et al.
"Correct tonotopic representation is necessary for complex pitch
perception", which appeared in Proc. Natl. Acad. Sci. USA, published online
before print January 12, 2004 (10.1073/pnas.0306958101).

This paper should be recommended to all who have to do with cochlear
implants. It is also of importance for physiological concepts of pitch. For
this reason I published a short comment on it:

http://w1.570.telia.com/~u57011259/Oxenham.htm

Martin

--------------------------------
Martin Braun
Neuroscience of Music
S-671 95 Klässbol
Sweden
web site: http://w1.570.telia.com/~u57011259/index.htm