Organization of auditory cortex in the owl monkey (Aotus trivirgatus)

Abstract

The best frequencies of single units and clusters of units in the superior temporal plane of the owl monkey were determined using threshold tone-burst stimulation. Following each experiment, brains were fixed, sectioned, and stained with thionin or cresyl violet. Electrode tracks were reconstructed from these sections and the cortical cytoarchitecture was examined. When the pattern of distribution of best frequencies and the cytoarchitecture are viewed in conjunction, five auditory fields may be defined. The strongest responses occur in two fields: (1) the primary field, which lies on the superior temporal plane caudal to the insula and extends a short distance onto the lateral surface, and (2) the rostral field, which borders the primary field rostrally. Best frequencies are well organized in these fields. Surrounding the primary and rostral fields are three cytoarhitectonically distinct fields. Here best frequencies are more difficult to define. Of these three fields, the most anterior and lateral are organized tonotopically, but we have not determined the organization of the caudomedial field.