Allocation of attention to programming of movement sequences in Parkinson's disease.

The allocation of attention to the programming and execution of movement sequences was examined in Parkinson's disease (PD). The time taken to initiate and execute sequences of one, three, and five button taps was examined, while also varying the hand used (left or right) and the attentional resources that could be allocated to sequencing (using single- versus dual-task conditions). These results showed that performance anomalies in PD were most apparent with the preferred right hand under single-rather than dual-task conditions. Subjects suffering from PD may tend to divert attention from the right hand under single-task conditions, and perhaps with short sequences, as well as being less likely to prepare sequences of more than three movements in advance with that hand. These effects were unlikely to reflect asymmetric pathology. If the right hand of such subjects has in some respects now come to behave more like a "clumsy" left hand, this may reflect a deliberate strategic choice in an attempt to cope with a movement impairment.