Basal ganglia and language: phonology modulates dopaminergic release.

Basal ganglia have been implicated in syntactic and phonological processes, but direct evidence has been scarce. Here, we used [11C]raclopride and positron emission tomography to measure modulations of the dopaminergic system induced by phonological or syntactic processing. Two significant effects were found. First, the level of accuracy in phonological processing significantly correlated with tracer binding potential in the left caudate nucleus. Second, the speed in phonological processing significantly correlated with tracer binding potential in the left putamen. Thus, a more accurate and fast phonological processing was associated with a reduced dopamine requirement in the left striatum. These findings show that the striatal dopaminergic system plays an essential role in grammatical processes that form the core of human language.