Cognitive and motor components of response speed in the Stroop test in Parkinson's disease patients

This study assessed the performance of patients with Parkinson's disease (PD) in the Stroop test. Twenty-seven patients with PD (17 men, 10 women; mean age, 63.3 ± 10.5 years) and 27 age-matched controls (14 men, 13 women; mean age, 63.5 ± 9.2 years) were administered the color-naming, word-reading, and incongruent color-word-naming tasks in the Stroop test. Compared with the normal control group, the PD group had slower speeds for all three tasks and greater Stroop interference, indicating a response inhibition deficit in PD patients. Further analysis indicated that slowness during color naming might be due to motor slowness, rather than a central cognitive processing problem in color discrimination. In conclusion, the performance of the PD group on the three tasks of the Stroop test suggests that the PD patients were deficient in motor responses and cognitive inhibitory abilities.