Flexibility of action verbs processing in Parkinson's disease

This study aims to investigate action language processing abilities in Parkinson's disease (PD) compared to healthy controls (HCs), specifically examining whether the involvement of motor systems is influenced by task context. By focusing on implicit versus explicit task demands, the study evaluates how semantic processing differs in PD and whether these differences align with a flexible embodied cognition framework.

The study analyzed the performance of participants on two tasks: an explicit task (semantic judgment task, SJ) and an implicit task (letter detection task, LD). PD outpatients (n = 31, mean age 64.58 years) referred to the Parkinson and Movement Disorders Unit of ICS Maugeri Hermitage were enrolled, along with a group of healthy controls (n = 31, mean age 64.19 years). Performance was measured through reaction times (RTs) and accuracy scores (Acc) during the processing of action verbs and abstract verbs.

PD patients exhibited slower RTs and lower accuracy when processing action verbs compared to abstract verbs, but only during the SJ task. Slower RTs in the SJ task were predicted by language and executive functioning (semantic fluency) and disease progression (Hoehn and Yahr stages) for both action and abstract verbs. In the LD task, slower RTs were predicted by executive functioning for action verbs and attention (measured by Trail Making Test Part B and Stroop task) for abstract verbs.

The findings suggest a context-dependent involvement of the motor system in action language processing, supporting a flexible, embodied approach to conceptual semantic processing rather than an automatic one.