Re: place pitch and temporal pitch

[Israel Nelken <israel@xxxxxxxxxxxxx>]

Dear Martin, list,
Martin Braun wrote:
> Also, such stimuli never occur in
> natural sounds. Therefore our hearing is not adapted to them.
       Almost pure tones at 4-5 kHz do occur in nature, in some bird songs.
See Bar-Yosef et al., J. Neurosci. 2002, for spectrograms. In general, I
think one should be careful when invoking natural sounds since the
auditory system of most mammals is pretty generalized. Cats evolved in
the desert, but do extremely well in modern cities. If there is
adaptation to natural sounds, one should look for it at a much higher
level of statistical structure (e.g. Nelken et al., Nature 1999).

       Regarding a previous comment by Christian Kaernbach:
> That is an important achievement of our brain: To present to us as
> unitary perception what is deduced from different cues. Another example
> would be spatial hearing: There are intensity differences, interaural
> time (!) differences, spectral (!) filtering by the outer ear, and even
> cues due to involuntary small head movements that interact perfectly so
> as to give a single percept of stereolocation. So pitch being a unitay
> percept does not rule out its relying on separate mechanisms.
       I couldn't agree more. I think that one should very carefully
discriminate between the 'features' that are used to build an auditory
percept, and the resulting perception. In the same sense that ITDs and
ILDs are not 'space' but rather parts of an integrated percept, spectral
and temporal cues for pitch are not 'pitch' but probably the building
blocks that are unified higher up.
       The same low-level - high-level perceptual difficulties are also
encountered in vision. For example, faces are perceived as whole things
- there's quite a good evidence for that today, but nobody would claim
that faces are extracted in the LGN or in V1. A psychological model that
tries to account for this discrepancy between immediate perception on
the one hand and the hierarchical, integrative processing of signal
features on the other hand was developed by Merav Ahissar and Shaul
Hochstein - I think this is worthwhile reading:
Hochstein and Ahissar, Neuron 36(5):791-804, 2002
       Eli





--
==================================================================
Israel Nelken
Dept. of Neurobiology
The Alexander Silberman Institute of Life Sciences
Edmond Safra Campus, Givat Ram    | Tel: Int-972-2-6584229
Hebrew University                 | Fax: Int-972-2-6586077
Jerusalem 91904, ISRAEL           | Email: israel@md.huji.ac.il
==================================================================