Neuropharmacology of language: ERP evidence for catecholaminergic modulation of syntactic processing.

A few studies have shown that brain catecholamines are implicated in language comprehension. However, the specific cognitive processes they modulate remain underexplored. We hypothesized that catecholamines enhance the unification of syntactic roles and word meanings into coherent multiword structures. This study combined electroencephalography and psychopharmacology to examine the effects of a catecholaminergic stimulant (methylphenidate) on processing sentences containing local syntactic ambiguities. Methylphenidate amplified the P600 event-related potential effect, which has been linked to the recruitment of cognitive resources for processing sentences with increased syntactic load. The drug's impact on semantic processing was subtler, showing a suggestive attenuation of the N400 effect to ambiguous sentences. Furthermore, the increase in the P600 effect under methylphenidate was most pronounced in participants with lower working memory capacity. This study provides evidence for linking catecholamine activity to syntactic unification in healthy individuals. Elevated catecholamine levels appear to increase the cognitive effort invested in syntactic unification, and to support the dynamic prioritization of syntactic information when contextual demands require it.