Sensorimotor dysfunction of grasping in schizophrenia: a side effect of antipsychotic treatment?

Antipsychotic treatment in schizophrenia is frequently associated with extrapyramidal side effects. Objective behavioural measures to evaluate the severity of extrapyramidal side effects in the clinical setting do not exist.

This study was designed to investigate grasping movements in five drug naive and 13 medicated subjects with schizophrenia and to compare their performance with that of 18 healthy control subjects. Deficits of grip force performance were correlated with clinical scores of both parkinson-like motor disability and psychiatric symptom severity

Participants performed vertical arm movements with a handheld instrumented object and caught a weight that was dropped into a handheld cup either expectedly from the opposite hand or unexpectedly from the experimenter's hand. The scaling of grip force and the temporospatial coupling between grip and load force profiles was analysed. The psychiatric symptom severity was assessed by the positive and negative symptom score of schizophrenia and the brief psychiatric rating scale. Extrapyramidal symptoms were assessed by the unified Parkinson's disease rating scale.

Drug naive subjects with schizophrenia performed similar to healthy controls. In contrast, medicated subjects with schizophrenia exhibited excessive grip force scaling and impaired coupling between grip and load force profiles. These performance deficits were strongly correlated with the severity of both extrapyramidal side effects related to antipsychotic therapy and negative symptoms related to the underlying pathology.

These data provide preliminary evidence that deficits of sensorimotor performance in schizophrenia are, at least in part, related to the side effects of antipsychotic treatment. The investigation of grasping movements may provide a sensitive measure to objectively evaluate extrapyramidal side effects related to antipsychotic therapy.