Josef P. Rauschecker
Lab. of Neuropsych., NIMH, Bldg. 49, Rm. 1B80, Bethesda, MD 20892-4415
Several auditory fields surrounding primary auditory cortex (AI) have been described in the rhesus monkey. Most recently, three areas have been identified in the so-called auditory belt region on the lateral surface of the superior temporal gyrus [Rauschecker et al., Science (1995) (in press)]. Functional identification of these lateral areas (AL, ML, and CL) was based on single unit responses to bandpassed noise (BPN) bursts, which constitute a class of superior stimuli for neurons in this region. Best center frequency (BFc) of the BPN bursts varies systematically along a rostro-caudal axis, revealing three cochleotopic maps. Neurons in the lateral areas also display tuning to a ``best bandwidth'' of the noise bursts, which varies along a medio-lateral axis, orthogonal to the BFc axis. Digitized vocalizations from the rhesus monkeys' own repertoire were finally used for presentation during single-unit recording. In many instances, neurons responded even better to the monkey calls than to noise bursts or other synthetic stimuli. It appears that the lateral belt areas of macaque auditory cortex could form an important step in the preprocessing of species-specific communication sounds, somewhat equivalent to superior temporal areas in humans that have been implicated in phonological processing.