Response properties of prefrontal visual neurons in the awake monkeys.

Abstract

Response properties of the visual neurons in the prearcuate and periprincipal areas of the prefrontal cortex were examined in awake monkeys. The findings obtained are as follows :(1) Most of the visual neurons responded with various excitatory fashions to a light spot presented in their visual receptive fields (RFs). The response was large when the stimulus was applied to the middle of the RF and became smaller when the stimulus position was moved from this part toward the RF border. (2) The response was affected by the size of the stimulus. The largest response was usually obtained by a small stimulus. The shape, orientation, brightness of the stimulus and the direction of its movement gave little influence on the response strength and pattern. (3) In about a half of the neurons the response was enhanced when the monkey made a saccadic eye-movement toward a visual stimulus in the RF. (4) Some of the above-mentioned response properties were quantitatively different from one another among neuron groups classified according to the eccentricity and size of their RFs. These results suggest that the properties of the neurons are suitable for detecting a visual stimulus occupying a limited extent in the space. prefrontal cortex ; visual neurons ; monkeyRecently several authors described that there were many visual neurons in the prearcuate and periprincipal areas of the monkey dorsolateral prefrontal cortex (Mohler et al. 1973;Pigarev et al. 1979;Mikami et al. 1982). Moreover, it was found that the neuronal location in the areas had a close relation to the eccentricity and the size of their visual receptive fields (RFs ; Suzuki and Azuma 1983). The neurons located in the lateral part of the areas had relatively small RFs in the central region of the visual field, while those in the medial part had large RFs in a considerably eccentric region of the contralateral visual field. Anteriorly located neurons had larger RFs than posteriorly located ones. Such systematic arrangement of the neurons in the cortical areas concerning the visual field may indicate that the areas contribute to obtaining the information of the visual space around the animal and subserve the localization of a stimulus in the space. It was expected that this suggestion was further verified by detailed investigation on the response properties of neurons in this wide areas. The purpose of the present