De ziekte van Parkinson en stoornissen in taalverwerking: waar zit de knoop?

De ziekte van Parkinson is na de ziekte van Alzheimer de meest voorkomende progressieve degeneratieve aandoening. Naast de motorische symptomen (namelijk bradykinesie, rigiditeit en rusttremor) die de kern van de klinische diagnose vormen, zijn cognitieve symptomen frequent aanwezig (Muslimović et al., 2005). De focus van het cognitieve onderzoek naar de ziekte van Parkinson is al decennialang gericht op de stoornissen van de executieve functies. Volgens recente ontwikkelingen neemt ook de kennis van de stoornissen van taalverwerking van patiënten met de ziekte van Parkinson toe. Desondanks blijven de precieze onderliggende processen die aan de basis liggen van stoornissen in het begrijpen en produceren van taal tot op heden nog onderwerp van discussie.

Abstract

Parkinson’s disease and dysfunctions in language processing

Parkinson’s disease (PD) is one of the most common progressive degenerative neurological diseases in which the dopaminergic afferents to the striatum are lost and striatal output via the direct and indirect pathways is altered. As a result PD patients often demonstrate a co-occurrence of their cardinal motor symptoms with subtle language processing impairments and other cognitive deficits. Indeed, neuropsychological deficits frequently occur in PD, even in early, untreated PD patients (Aarsland et al., 2009). Domains that are typically affected include executive functions, attention, memory, and visuospatial skills (Dubois & Pillon, 1995, 1997; Green et al., 2002; Muslimovic et al., 2005; Pillon, Czernecki & Dubois, 2003). Although the focus of many cognitive studies is on the typically disturbed executive functions deficits, recent work has shown that alterations in linguistic routines are also often present.

This paper gives an overview of recent behavioural and functional imaging research on the underlying causes of the language impairments in non-demented PD patients. Two major research questions were put forward. By using behavioral and neuroimaging experiments, it was first investigated whether syntactic sequencing was disturbed in Dutchspeaking patients with PD who were also known to have difficulties in performing sequences of voluntary movements. Secondly, we examined the interaction of executive functioning on language processing in PD patients compared to ageand education-matched healthy control participants.

In conclusion, our experimental results showed that PD patients have a disturbance in processing word order and that there does not appear to be a language faculty independent from executive control.