Re: Pitch neurons (was "Autocorrelation-like ...")

[Martin Braun <nombraun@xxxxxxxxx>]

Peter Cariani asked:

> It would solve the problem if IC units with 300 Hz BFs also responded
> to AM tones with Fm's of 300 Hz and carriers at 1 kHz. Unfortunately, I
> know of no evidence for such responses (if you have seen such things or
> know of a suitable reference, I would be more than happy ....

Ulrich Biebel and Gerald Langner have reported precisely this on several
occasions over the past seven years. They presented their results at the
Prague conference in 1996, had them in the proceedings of this conference
from 1997, and finally published a comprehensive report on the matter in
Hearing Research in 2002. Because of the importance of their findings I have
also discussed and referenced them twice on this list. See in the list
archives under:

October 21-2000, and
October 01-2002.

As to the relevance of the results, I had written earlier:
"Recent results by Biebel and Langner (1997) further indicate that the
multiple detection of one identical f0 in different regions of the ICC is
apparently pooled already within this nucleus, i.e. at the CF location
corresponding to f0.
For example, a complex tone with the partials 900, 1200, 1500, and 1800 Hz
can cause a lamina-based detection of one identical f0 = 300 Hz in three
different lamina pairings: (1) lamina containing CF of 900 Hz paired with
lamina containing CF of 1200 Hz, (2) 1200 Hz with 1500 Hz, and (3) 1500 Hz
with 1800 Hz.
Biebel and Langner (1997) now found in the chinchilla ICC that low frequency
units (e.g., CF =170 Hz) respond maximally to various high frequencies, if
the stimulus amplitude is modulated by a frequency that is equal, or very
close, to the unit's CF. These units respond to various carrier frequencies
with a BMF that matches their CF. The authors suggested that such units,
termed pitch neurons, are capable of pooling multiple identical f0
extractions from various ICC loci." (Braun, 1999, p 80)


> For chords, one can often hear out the pitches of the constituent notes
> (see Parncutt's book, which has pitch matches for chords in it ....

In the case of a pitch-match task we have a frequency-specific increase in
top-down signaling. Such signaling selectively facilitates the extraction of
one particular pitch in the inferior colliculus. Also on this issue we have
compelling experimental evidence, including brainstem electrophysiological
recordings from the scalp in humans. It is reviewed in Braun (2000).


> I think it's difficult to rule out subcortical timbre discrimination at
> this point. Why do you think it's not possible?

Peter, for timbre perception you need reference to a timbre lexicon: angry
dog, happy dog, piano bass range, piano middle range, etc. There is no place
for such a lexicon anywhere below the auditory cortex.


> Maybe our quibble is semantic. If you see pitch neurons that "do all
> what autocorrelators can", then functionally they are autocorrelators,

This is correct. But you do not call a horse a motor bike, just because you
can ride on both ;-)

-----------------------------
Biebel, U.W., Langner, G. (1997). Evidence for "pitch neurons" in the
auditory midbrain of chinchillas. In: Syka, J. (Ed.), Acoustic Signal
Processing in the Central Auditory System. Plenum Press, New York, pp.
263-269.

Ulrich W. Biebel and Gerald Langner (2002). Evidence for interactions across
frequency channels in the inferior colliculus of awake chinchilla. Hear.
Res. 169, 151-168.

Braun, M.(1999) Auditory midbrain laminar structure appears adapted to f0
extraction: further evidence and implications of the double critical
bandwidth. Hear. Res. 129, 71-82.

Braun, M. (2000) Inferior colliculus as candidate for pitch extraction:
multiple support from statistics of bilateral spontaneous otoacoustic
emissions. Hear. Res. 145, 130-140.

Martin

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