Learning arbitrary visuomotor associations: Temporal dynamic of brain activity

Primates can give behavioral responses on the basis of arbitrary, context-d ependent rules. When sensory instructions and behavioral responses are asso ciated by arbitrary rules, these rules need to be learned. This study inves tigates the temporal dynamics of functional segregation at the basis of vis uomotor associative learning in humans, isolating specific learning-related changes in neurovascular activity across the whole brain. We have used fMR I to measure human brain activity during performance of two tasks requiring the association of visual patterns with motor responses. Both tasks were l earned by trial and error, either before (visuomotor control) or during (vi suomotor learning) the scanning session. Epochs of tasks performance (simil ar to 30 s) were alternated with a baseline period over the whole scanning session (similar to 50 min). We have assessed both linear and nonlinear mod ulations in the differential signal between tasks, independently from overa ll task differences. The performance indices of the visuomotor learning tas k smoothly converged onto the values of a steady-state control condition, a ccording to nonlinear timecourses. Specific visuomotor learning-related act ivity has been found over a distributed cortical network, centred on a temp oro-prefrontal circuit. These cortical time-modulated activities were suppo rted early in learning by the hippocampal/parahippocampal complex, and late in learning by the basal ganglia system. These findings suggest the inferi or temporal and the ventral prefrontal cortex are critical neural nodes for integrating perceptual information with executive processes. (C) 2001 Acad emic Press.