Pitch neurons (was "Autocorrelation-like ...") (Martin Braun )

Subject: Pitch neurons (was "Autocorrelation-like ...")
From:    Martin Braun  <nombraun(at)TELIA.COM>
Date:    Wed, 5 Mar 2003 12:13:42 +0100

Peter Cariani wrote: > Modulation-tuned units have been found in abundance, but there are some > basic problems with these when it comes to pitch: > 1) they cannot explain pitch equivalence between pure and complex tones > (big, big problem) No problem. F0 periods that arise in the frequency laminae of the partials are forwarded to the frequency laminae of F0. > 2) they are not likely to represent multiple competing pitches in a > robust fashion (e.g. two musical instruments playing notes a third > apart --) We only hear two pitches, if there are strong timbre labels attached to them. These are decoded in the cortex, which then feeds back to the pitch neurons in the midbrain. > 3) they are not likely to yield a representation that does not degrade > at high SPLs Level stability is provided by lamina-based lateral inhibition in the midbrain. > 4) they are not likely to explain the pitch shifts of inharmonic > complex tones Period detectors register these pitch shifts, as calculated many years ago. > 5) it's not clear if predicted pitches of low harmonics will be > invariant with respect to phase spectrum (as they should be) There are plenty of possibilities for phase resetting between cochlea and midbrain. In general: There is not one observation, either psychoacoustic or physiological, that is not compatible with pitch extraction in the central nucleus of the inferior colliculus by periodotopic arrays of tuned pitch neurons. The evidence for this mechanism has accumulated since 1987. For reviews: http://w1.570.telia.com/~u57011259/eng5.htm For some recent evidence: http://w1.570.telia.com/~u57011259/Galazyuk.htm Martin ------------------------------------------- Martin Braun Neuroscience of Music S-671 95 Klassbol Sweden e-mail: nombraun(at)telia.com web site: http://w1.570.telia.com/~u57011259/index.htm

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