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Re: Pitch orientation-discriminating feature detectors?

Dear Eliot,

There is a perceptual asymmetry that is linked to the direction of
pitch movement. Frequency peaks (upward-then-downward frequency
modulation) are more salient and produce much lower difference limens
than frequency troughs (downward-then-upward FM). This has been
described in detail by Demany and colleagues in a series of studies
published in JASA (see refs below).

We are in fact starting a project to record cortical activity
associated with FM peaks and troughs, using magnetoencephalography --
together with Laurent Demany and Andre Rupp. What we see up to now is
that the source waveforms in response to FM peaks consistently display
longer N1 latencies and larger N1-P2 amplitudes, when compared to
responses to matched FM troughs.

Such an asymmetry might have something to do with previous reports of
EEG recordings examining upward vs. downward frequency glides. For
instance, Ruhm (1971) showed that upward glides produce bigger and
later N1-P2 responses than downward glides.

The next question is of course why would it be useful in the real
world to process differently upward vs. downward frequency




  author =       {Demany, L. and McAnally, K.},
  title = {The perception of frequency peaks and troughs in wide
  frequency modulations},
  journal =      {J. Acoust. Soc. Am.},
  year =         1994,
  volume =       96,
  pages =        {706-715}

  author =       {Demany, L. and Clément, S.},
  title = {The perception of frequency peaks and troughs in wide
  frequency modulations. II. Effects of frequency register, stimulus
  uncertainty and intensity},
  journal =      {J. Acoust. Soc. Am.},
  year =         1995,
  volume =       97,
  pages =        {2454-2459}

[there are two other Demany and Clément papers in JASA, 1995 and 1997]

  author =       {Ruhm, H. B.},
  title = {Directional sensitivity and laterality of electroencephalic
  responses evoked by acoustic sweep frequencies},
  journal =      {J. Auditory Res.},
  year =         1971,
  volume =       11,
  pages =        {9-16}