VISUAL FEATURE SELECTIVITY IN FRONTAL EYE FIELDS INDUCED BY EXPERIENCE IN MATURE MACAQUES

WHEN examining a complex image, the eye movements of expert observers differ from those of novices; experts have learned to ignore features that are visually salient but are not relevant to the interpretation o f the image(1-3). We have studied the neural basis of this form of per ceptual-motor learning using monkeys that have learned to search for a visual target among distracters, Monkeys trained to search only for, say, a red stimulus among green distracters will ignore green stimuli even if they subsequently appear as targets in a complementary search array, that is, among red distracters, We recorded from neurons in the frontal eye field (FEF), a cortical area that responds to visual stim uli and controls purposive eye movements(4-6). Normally, FEF neurons d o not exhibit feature selectivity, but their activity evolves to signa l the target for an incipient eye movement(7). In monkeys trained excl usively on targets of one colour, however, FEF neurons show selectivit y for stimuli of that colour, Because this selective response occurs s o soon after presentation of the stimulus array, and is independent of location within the visual field, we propose that it reflects a form of experience-dependent plasticity that mediates the learning of arbit rary stimulus-response associations.