Concurrent performance of motor tasks and processing capacity in patients with schizophrenia

Any task is carried out more successfully if we allocate undivided attentio n to it, but as demands on attentional capacity increase-for example, in co ncurrent or dual task conditions-performance on attended tasks becomes more impaired. Patients with schizophrenia show impaired performance on tasks r equiring high levels of attentional capacity. This study examines performan ce of 11 patients with schizophrenia and 13 normal controls on two motor ta sks (placing pegs in a pegboard and repetitive index finger tapping) under unimanual, bimanual, and dual task conditions. The patients with schizophre nia placed fewer pegs and had reduced tapping speed in unimanual and bimanu al conditions. However, the decrement in bimanual performance as a percenta ge of unimanual performance was not significantly different for the patient s and controls on either the pegboard or tapping tasks. By contrast, under dual task conditions, the performance of the patients with schizophrenia in peg placement actually improved relative to the unimanual pegboard task, w hereas tapping performance deteriorated compared with the unimanual tapping , a decrement that was significantly greater for the patients. Thus the imp rovement in the visually guided pegboard task was at the expense of the rep etitive tapping task. These results are discussed in terms of an impairment of self initiated movement with general sparing of externally triggered mo vements in schizophrenia and the role of frontostriatal loops in this proce ss.