The striatum is thought to play an essential role in the acquisition of a w
ide range of motor, perceptual, and cognitive skills, but neuroimaging has
not yet demonstrated striatal activation during nonmotor skill learning. Fu
nctional magnetic resonance imaging was performed while participants learne
d probabilistic classification, a cognitive task known to rely on procedura
l memory early in learning and declarative memory later in learning. Multip
le brain regions were active during probabilistic classification compared w
ith a perceptual-motor control task, including bilateral frontal cortices,
occipital cortex, and the right caudate nucleus in the striatum. The left h
ippocampus was less active bilaterally during probabilistic classification
than during the control task, and the time course of this hippocampal deact
ivation paralleled the expected involvement of medial temporal structures b
ased on behavioral studies of amnesic patients. Findings provide initial ev
idence for the role of frontostriatal systems in normal cognitive skill lea
rning.