[Effects of advance information given by sensory cues on the duration and precision of a pointing movement in Parkinson's disease]

The aim of the present study was to investigate Parkinsonians' ability to process and use the explicit and implicit advance information available about a motor task they are preparing to perform. For this purpose, the performances of 13 Parkinsonians were compared with those of 11 control subjects in a double stimulus reaction time task. The explicit information was provided by a preparatory auditory signal (S1), and the implicit information was conveyed by the probability that the imperative signal (S2) would be consistent with S1 in a given series of trials. Each subject performed 3 successive RT tasks under the following conditions: an oriented cue condition, a neutral cue condition and a primed condition. The results show that the movement times of the Parkinsonians were longer than those of the control subjects, and that they lengthened with the clinical evolution of the disease. Neither the explicit nor the implicit advance information had any effect on the control subjects' performance variables; nor did they affect the Parkinsonians' movement times or pointing areas. The Parkinsonians' systematic errors increased however in the case of primed responses. The fact that the patients' bradykinesia was associated with fairly accurate pointing performances suggests that in Parkinson's disease, a change of voluntary movement performance strategy may occur, involving greater reliance on visual cues.