Click train encoding in primary auditory cortex of the awake monkey: Evidence for two mechanisms subserving pitch perception

Mitchell Steinschneider, David H. Reser, Yonatan I. Fishman, Charles E. Schroeder, Joseph C. Arezzo

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Multiunit activity (MUA) and current source density (CSD) patterns evoked by click trains are examined in primary auditory cortex (A1) of three awake monkeys. Temporal and spectral features of click trains are differentially encoded in A1. Encoding of temporal features occurs at rates of 100-200 Hz through phase-locked activity in the MUA and CSD, is independent of pulse polarity pattern, and occurs in high best frequency (BF) regions of A1. The upper limit of ensemble-wide phase-locking is about 400 Hz in the input to A1, as manifested in the cortical middle laminae CSD and MUA of thalamocortical fibers. In contrast, encoding of spectral features occurs in low BF regions, and resolves both the f0 and harmonics of the stimuli through local maxima of activity determined by the tonotopic organization of the recording sites. High-pass filtered click trains decrease spectral encoding in low BF regions without modifying phase-locked responses in high BF regions. These physiological responses parallel features of human pitch perception for click trains, and support the existence of two distinct physiological mechanisms involved in pitch perception: the first using resolved harmonic components and the second utilizing unresolved harmonics that is based on encoding stimulus waveform periodicity.

Original languageEnglish
Pages (from-to)2935-2955
Number of pages21
JournalThe Journal of the Acoustical Society of America
Issue number5
Publication statusPublished - 1998
Externally publishedYes

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