How dopamine influences language processing in the brain

Do neurotransmitters such as dopamine and noradrenaline (catecholamines) influence language processing? In a neuroimaging study published in PNAS, a team of researchers led by the Max Planck Institute for Psycholinguistics (MPI-PL) in Nijmegen recorded brain activity of healthy adults during sentence comprehension, after raising catecholamine levels with stimulant medication (methylphenidate). Higher catecholamine levels led to stronger recruitment of cognitive resources during processing of grammatically ambiguous sentences, showing how neurochemical systems may shape language processing.

The neurotransmitters dopamine and noradrenaline both belong to the class of catecholamines. “Catecholamines are known to regulate attention, working memory, and cognitive control, but their role in language remains poorly understood”, says Peter Hagoort, senior investigator and director emeritus of MPI-PL’s Neurobiology of Language Department and the Donders Institute for Brain, Cognition and Behaviour. 

“Our earlier work suggested that catecholamines can affect semantic aspects of sentence comprehension. Whether these neuromodulatory systems also influence syntactic processing—how the brain combines words into grammatical structures—was largely unknown.”

Metylphenidate, commonly used as a treatment for ADHD, increases catecholamine levels. Would the stimulant affect the neural processes involved in syntactic processing?

Garden-path sentences

To study syntactic processing, the researchers used temporarily ambiguous ‘garden-path’ sentences. When such sentences are presented word-by-word, readers are led ‘up the garden path’, as their first interpretation is likely to be incorrect. In ‘The fan attacked the drummer and the guitarist packed the instruments up’, most readers will interpret ‘the drummer and the guitarist’ as a unit. After encountering ‘packed’, readers need to revise their initial interpretation, based on the grammatical structure of the sentence.

A group of 30 healthy adults read ambiguous and unambiguous sentences while their brain activity was recorded with EEG (electroencephalography). They also answered comprehension questions after each sentence. Each participant was tested twice; once after taking methylphenidate and once after taking a placebo.

Enhanced P600 response

Methylphenidate enhanced the P600 response to the garden-path sentences, measured at the critical word (‘packed’). This well-known EEG response occurs when syntactic processing is demanding, reflecting greater cognitive effort. The increase in the P600 effect was strongest in participants who had lower baseline working memory capacity.

“The findings suggest that catecholaminergic systems contribute to the dynamic allocation of cognitive resources during syntactic processing”, says Hagoort. “Their influence on language therefore appears to extend beyond semantic processing to syntactic unification, and the magnitude of this effect may depend on individual baseline working memory performance.”

“The results support the development of neuropharmacolinguistics as a field linking neuromodulatory systems to language processing.”

Publication

Yingying Tan, Ashley G. Lewis, Iris C. Schmits, Robert-Jan Verkes, Roshan Cools & Peter Hagoort, (2026). Neuropharmacology of language: ERP evidence for catecholaminergic modulation of syntactic processing. Proceedings of the National Academy of Sciences. doi.org/10.1073/pnas.2606806123