Thalamic encoding of lexical status is lateralized during reading aloud

To explore whether the thalamus participates in lexical status encoding, local field potentials were recorded in patients undergoing deep brain stimulation lead implantation while they read aloud single-syllable words and nonwords. Bilateral decreases in thalamic beta (12-30Hz) activity were locked preferentially to stimulus presentation, and these decreases were greater when nonwords were read, demonstrating bilateral sensitivity to lexical status. Increased broadband gamma (70-150Hz) activity bilaterally was locked preferentially to speech onset, but greater nonword-related increases in broadband gamma activity were observed only on the left, demonstrating lateralization of thalamic lexical status effects. In addition, this lexical status effect on broadband gamma activity was strongest in more anterior thalamic locations, regions more likely to receive pallidal than cerebellar afferents. These results are the provide direct evidence from intracranial thalamic recordings for the lateralization and topography of subcortical lexical status processing.