Responses of cells in the superior colliculus of the squirrel monkey to auditory stimuli

Forty-two cells in the superior colliculus of awake squirrel monkey (Saimiri sciureus) were tested for their responses to pure tones and to 7 different species-specific vocalizations. Thirty-six cells responded to at least one of the auditory stimuli. Of the responding cells 94% responded to at least one vocalization. Pure tones were less effective and elicited a response in only 69%. Based on the effective bandwidths, cells could be divided into two subgroups: narrowly tuned cells with bandwidths of 0.08-2 octaves, and broadly tuned cells with bandwidths of 4-6 octaves. All the narrowly tuned cells responded to the effective frequencies with simple, short and similar patterns. Most of the broadly tuned cells, on the other hand, exhibited more complex, and longer response patterns which were frequency-dependent. The various vocalizations elicited in most cells simple, short and similar response patterns. In several cells, however, these vocalizations elicited more complex, longer and different response patterns. Cells which exhibited simple and short patterns in response to vocalizations were evenly distributed among the narrowly and broadly tuned cells. All the cells which exhibited the more complex response patterns to vocalizations were broadly tuned.