Repetition priming effects in monkey cortex: an fMRI Study

Wednesday, October 26, 2011 — Poster Session IV
2:00 p.m. – 4:00 p.m.	Natcher Conference Center	NIMH	NEURO/BEHAV/SENSYS-19

Authors

• D McMahon
• A Kurnikova
• C Zhu
• H Merkle
• F Ye
• D Leopold

Abstract

When something happens for the first time, it may catch us by surprise. When it happens again, we tend to be prepared. In humans, repetition-induced priming of behavioral responses is accompanied by activity reductions in extrastriate visual and prefrontal cortices. How faster or more efficient behavioral responses can arise from activity decreases in the same brain regions that are responsible for generating that behavior has remained a long-standing mystery. To investigate the brain mechanisms that give rise to priming of behavioral reaction times, we performed and event-related fMRI study in two monkeys trained to perform a symmetry decision task. On each trial, the monkeys pulled a lever with either their left or right hand depending whether a stimulus was symmetric or asymmetric. The monkeys responded faster upon seeing a stimulus that they had seen before, particularly after short-lag repeats. During behavioral performance we observed robust task-related brain activation throughout the ventral visual pathways, including V4, TEO, and anterior TE, as well as in the ventral premotor area. This activation was substantially reduced by stimulus repetitions, particularly when images were repeated at short lags. Our findings establish an overall homology between the general circuitry underlying priming between humans and monkeys.

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