Stimulus-induced behavior has been classically interpreted as an interaction between ‘sensory systems’ and a ‘motor system’ through the involvement of an ‘association system’. In this research we studied some aspects of the role of the auditory cortex in the process of sensorimotor association. The activity of 146 units in the auditory cortex of a rhesus monkey was recorded during performance of an auditory discrimination reversal task in which each of two stimuli was associated with one of two learned motor responses. Seventy-two units were in koniocortex areas Kam and Kalt; 74 units were in the lateral portion of the belt area (PaAlt). The units were recorded from 40 recording sites; 2 to 6 single units were recorded simultaneously in each site. We found that a) the spike activity of a fraction (9-17%) of the units in the auditory cortex reflected the process of sensorimotor association; b) these neurons had a component of their evoked response that is sensory and a component that reflected sensorimotor association; c) units exhibiting association activity did not show any clustering; and d) on the average, units of the koniocortex tended to respond strongly and with shorter latency to sound stimuli than units of the lateral belt area; however, units exhibiting sensorimotor association activity were equally distributed in both areas. On the basis of these findings it is suggested that the association system need not be separated anatomically from the cortical sensory system. We suggest that the mechanisms by which sensorimotor association occurs may be better studied in further research on the basis of the premise that a single neuron can participate in the performance of different functions.
Single-unit activity related to sensorimotor association in auditory cortex of a monkey
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