Retention of perceptual categorization following bilateral removal of area TE in rhesus monkeys

Abstract

Event Abstract Back to Event Retention of perceptual categorization following bilateral removal of area TE in rhesus monkeys Narihisa Matsumoto1, 2*, Richard Saunders1, Katalin Gothard3 and Barry Richmond1 1 NIMH/NIH, Japan 2 NIMH/NIH, AIST, Japan 3 University of Arizona, United States Bilateral ablation of inferior temporal (IT) cortex impairs pattern discrimination in monkeys [1,2]. Single neurons in area TE of IT cortex have marked tuning to visual stimuli like objects or faces [3-5]. Physiological recordings (single neuron and fMRI) show activity grouped into categorical-like functions (face and non-face patches) [6-10]. These findings lead to the hypothesis that area TE plays a critical role in categorizing objects or faces. To test this hypothesis, monkeys were tested before and after bilateral removals of area TE on a task that requires the association of 2 perceptual categories (e.g. human faces vs. monkeys faces) of visual stimuli with different incentive values. In the task the monkey grasps and holds a bar, a visual cue appears for 400 ms, and then a red dot appears in the center of the stimulus, 500-1500 ms later the red dot changes to green. If the monkey releases the bar within 3 seconds after the dot changes to green, the color of the dot changes to blue and in high incentive trials a liquid reward is also delivered. In low incentive trials the trial ends. After an intertrial interval a new cue is chosen pseudorandomly for the next trial. We used 20 dogs/20 cats, or 20 human/20 monkey faces for the visual cues. Before TE ablations, the monkeys made significantly more errors in trials with low incentive stimuli than in trials with high incentive stimuli (p