Vision Forum 2002: the 6th meeting "The Neural basis of early vision"ij2002.9

Visual response properties of presumed inhibitory neurons in the macaque inferior temporal cortex

1Graduate School of Frontier Biosciences, Osaka University, Toyonaka, Osaka, 560-8531, Japan, 2National Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki, 305-8566, Japan, 3Core Research for Evolutional Science and Technology, Japan Science and Technology Corporation, Toyonaka, Osaka, 560-8531, Japan

Hiroshi TAMURAo,1,2, Hidekazu KANEKO2, Keisuke KAWASAKI1,3, and Ichiro FUJITA 1,3

ABSTRACT(<300: 277)
Neurons in area TE of the monkey inferior temporal cortex respond to images of particular objects or their visual features. The neural basis of their response selectivity of TE neurons is largely unknown. We addressed the question of how inhibitory interaction within TE contributes to the selectivity by examining visual response properties of presumed inhibitory neurons. Extracellular neuronal recordings were performed with a multi-probe electrode in area TE of 4 anesthetized monkeys (Macaca fuscata), and up to 12 neurons were simultaneously recorded from a single site. Cross-correlation analysis was applied to spike trains recorded simultaneously from a pair of adjacent neurons. A neuron in a pair whose activity was followed by a decrease in activity of its partner was presumed to be an inhibitory neuron. Out of 455 neurons recorded from area TE, 49 were considered as inhibitory neurons. Most of the presumed inhibitory neurons were visually responsive and had a clear stimulus preference. On average, they increased firing rates to 10% of the stimuli in our stimulus set consisting of several dozens geometrical figures and photographs of objects. Similarity in overall stimulus preferences was lower between members of a pair of neurons with an inhibitory linkage than those with common inputs and/or an excitatory linkage. Further, the less similar the overall stimulus preferences were, the stronger the inhibitory interactions were. The results indicate that inhibitory neurons in area TE are driven selectively by particular visual images, and robust inhibition occurs among adjacent neurons with different overall stimulus preferences, suggesting that local inhibitory interactions contribute to shaping the stimulus selectivity of TE neurons.