Subcortical Contributions to Language

While it is well established that language processing is dependent on cortical mechanisms, the role of the subcortex in language function has been a point of contention since the initial clinical-anatomical observations of language deficits following vascular subcortical lesions. This chapter reviews both traditional proposals and recent discoveries of the functional and structural connectivity of the basal ganglia and thalamus with the cortex, suggesting that these subcortical structures are well positioned to contribute to language processing. It then examines both patient and healthy neuroimaging data implicating the thalamus and basal ganglia in various aspects of language, including lexical-semantics, verb/action processing, grammar, and sentence comprehension. While there is still considerable conjecture regarding the role of the basal ganglia in a number of these operations, there is now considerable evidence that the thalamus influences lexical-semantic processing through attentional engagement, while striatal-thalamic-cortical circuits most likely influence lexical-semantic functions, bilingual language processing, and sentence comprehension through domain-general mechanisms, including controlled selection and suppression.