Investigation of supervisory attentional system functions in patients with Parkinson's disease using the Hayling task.

The study explored executive dysfunction in Parkinson's disease (PD) by using the Hayling test (Burgess & Shallice, 1996) and verbal fluency tasks (VFTs). PD patients showed longer response latencies than controls in both parts of the Hayling test (Section A/automatic and Section B/inhibition). Patients and controls did not differ in the proportion of errors or number of responses that revealed the use of strategies. PD patients also showed verbal fluency deficits in semantic, phonemic, and alternating fluency tasks. These impairments on tests known to be sensitive to frontal lobe dysfunction confirm executive or Supervisory Attentional System (Norman & Shallice, 1986) deficits and further indicate suppression skills impairments in PD.