Inferior colliculus as candidate for pitch extraction:
multiple support from statistics of bilateral spontaneous otoacoustic
emissions
Martin Braun
Hear Res 2000, 145, 130-140
Abstract
The fibrodendritic laminae of the central nucleus of the inferior colliculus
(ICC) constitute a frequency map in stacked sheets that are consistently
related to the psychoacoustic critical bandwidth (CB) (Schreiner and Langner,
1997, Nature 388, 383-386). The recently observed co-occurrence of the
CB and the double CB (2CB) suggested an adaptation of the ICC frequency
map to the extraction of the fundamental frequency f0 (Braun, 1999,
Hear. Res. 129, 71-82). The present study examined a possible influence
of this frequency map upon efferent signaling towards the cochlea. The
f0 distribution of 2890 monaural and 2604 binaural pairs of human
spontaneous otoacoustic emissions (SOAEs) was analyzed by three statistical
methods and in each case showed non-random behavior in the CB-2CB range.
Single results were (1) a bias of right ear f0 (mode at 349 Hz)
and left ear f0 (mode at 262 Hz) towards different ranges of speech
f0 (P < 0.02); (2) a bias of binaural - but not monaural - f0
towards 5 of 12 semitone bins, C-G-D-A-E, representing the most frequent
tones in music (P < 0.003); (3) a bias of binaural - but not monaural
- f0 fine-distribution towards the exact pitch frequencies used
in music, according to the international standard A4 = 440 Hz (p = 0.03).
The results support a model of lamina-based f0 extraction in the
ICC and suggest a specific colliculo-cochlear feedback for f0
enhancement.
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