Auditory cortex and the pitch of complex tones.

Two cats were trained to discriminate between rising and falling pitch sequences generated by complex tones. The finding of Heffner and Whitfield [J. Acoust. Soc. Am. 59, 915-919 (1976)], that the intact animals respond to the fundamental pitch rather than to the harmonic content, was confirmed. After bilateral ablation of auditory cortex this was no longer the case. The animals lost their initial training, but could be retrained to respond to the complex tone sequences; however, they now required to be separately trained to each complex tone and did not exhibit transfer between tone pairs that had similar pitch shift but different harmonic composition. The results suggest that cats without auditory cortex respond only to the individual frequencies of the complex and are unable to detect the overall pitch to which those complexes normally give rise.