An electrophysiological investigation of the effects of levodopa on semantic comprehension of action words in Parkinson’s Disease

Patients with Parkinson’s Disease (PD) evidence an impairment of implicit language processing, specifically for phonology, morphology and syntax.The current manuscript reports an electrophysiological investigation of semantic comprehension of action words in PD. In seven patients with advanced PD, we investigated the dopaminergic effects on action-word comprehension by means of event-related potentials. The patients were asked to silently read a randomized series of verbs, consisting of hand action and non-action verbs. Using LORETA-analysis, the current densities in ten brain areas of interest were studied over a predefined time window from 150 to 260 ms after word onset. Higher current densities were found after levodopa administration. In 5/7 patients a temporal increase in current density was found in these areas between 200 and 230 ms after word onset. In 1 of these 5 patients, this occurred only during the on-evaluation. Moreover, our results suggest a laterality of these effects, corresponding with the laterality of clinical motor signs. These results are discussed in a broad context of neuromodulatory influence of dopamine on semantic activation and lateralized physiological changes in PD.

► We report an ERP-study of semantic comprehension of action words in PD.
► Higher current densities were found after levodopa administration.
► In 5/7 patients a temporal increase in current density was found.
► Our results suggest a laterality of these effects.
► This laterality corresponds to motor asymmetry.