The context of uncertainty modulates the subcortical response to predictability

Implicit motor learning tasks typically involve comparisons of subject resp onses during a sequence versus a random condition. In neuroimaging, brain r egions that are correlated with a sequence are described, but the temporal relationship of sequence versus nonsequence conditions is often not explore d. We present a functional magnetic resonance imaging (fMRI) study describi ng activation related to sequential predictability in an implicit sensorimo tor learning task and the history (context) dependence of these effects. Pa rticipants regarded four squares displayed horizontally across a screen and pressed a button when any one of the four targets was illuminated in a par ticular color. A repeating spatial sequence with varying levels of predicta bility was embedded within a random color presentation. Both the right dors olateral prefrontal cortex (R DLPFC) and right caudate displayed a positive correlation to increasing predictability, whereas the left posterior parie tal cortex (L PPC) displayed a negative correlation. However, the activatio n changes within the caudate were significant when transitioning from high predictability to low predictability but not for the reverse case, suggesti ng a sensitivity not only to predictability but to order effects as well. T hese results support the hypothesized relationship between basal ganglia an d visuomotor sequential learning, but demonstrate the importance of context upon sequence learning.