Parkinson’s disease undermines language processing

University of Groningen researcher Katrien Colman has found clear indications of this in Dutch native speaker patients. She will be awarded a PhD by the University of Groningen on 17 February 2011. Colman: 'We could spare patients a lot of suffering if we learn to better understand their language processing problems.'

The more the population ages, the more cases there will be of Parkinson's disease. The general public mainly recognizes Parkinson's through its motor symptoms. Patients have trembling hands or arms, stiff limbs and walk bent over, shuffling. Well-known patients included Prince Claus, consort to Queen Beatrix of the Netherlands, and Pope John Paul II.

Stiff limbs

Parkinson's disease is caused by a shortage of dopamine in the brain. A lack of this neurotransmitter leads not only to the familiar motor symptoms, but also affects the executive brain functions of the patient; in other words, their ability to guide their own behaviour in new, non-routine situations. Examples include systematic actions, foreseeing consequences and resolving problems flexibly.

Stilted sentences

Katrien Colman demonstrated that impairment of the executive functions also affects language processing. For example, impairment of the executive brain function can result in a patient no longer understanding a complicated sentence construction: before the patient reaches the end of the sentence, he or she has forgotten how it began. Impairment of flexibility means that the patient has difficulty in changing the subject, even if there is a clear reason to do so. Impairment of the ability to work in a structured way means that it becomes difficult to construct grammatically correct sentences.

Aphasia: a different problem

The language processing problems of Parkinson's patients are sometimes compared with those of aphasia patients -- often incorrectly, as revealed by Colman's research. Aphasia, for example as the result of an infarct, can affect the grammatical ability itself, meaning that the patient can no longer conjugate a verb. The patient can then, for example, no longer derive the past participle 'walked' from the infinitive 'to walk'. With Parkinson's patients, this specific grammatical ability is not affected but rather the underlying executive function. The patient is then in principle able to derive a past participle, but in some situations does not do so -- for example because he can no longer view the sentence as a whole.

The research reveals that the language processing problems of Parkinson's patients deserve serious attention. Colman said, 'If communication is difficult, this does not necessarily mean that the patient is tired or depressed, or that there's something wrong with his intelligence.' Patients can be helped if people communicate with them in simple sentences, but it would be wrong to treat them as children. Colman: 'We could spare patients a lot of suffering if we learnt to better understand their language impairments and developed suitable ways to communicate with them.'