Abstract
ABSTRACTIntroduction: Motor slowness (bradykinesia) is a core feature of Parkinson’s disease (PD). It is often assumed that patients show mental slowness (bradyphrenia) as well; however, evidence for this is debated. The aims of this study were to determine whether PD patients show mental slowness apart from motor slowness and, if this is the case, to what extent this affects their performance on neuropsychological tests of attention, memory, and executive functions (EF). Method: Fifty-five nondemented PD patients and 65 healthy controls were assessed with a simple information-processing task in which reaction and motor times could be separated. In addition, all patients and a second control group (N = 138) were assessed with neuropsychological tests of attention, memory, and EF. Results: While PD patients showed significantly longer reaction times than healthy controls, their motor times were not significantly longer. Reaction and motor times were only moderately correlated and were not related to clinical measures of disease severity. PD patients performed significantly worse on tests of attention and EF, and for the majority of neuropsychological tests 11–51% of the patients showed a clinically impaired performance. Reaction times did not, however, predict patients’ test performance, while motor times were found to have a significant negative influence on tests of attention. Conclusions: PD patients show mental slowness, which can be separated from motor slowness. Neuropsychological test performance is not influenced by mental slowness; however, motor slowness can have a negative impact. When interpreting neuropsychological test performance of PD patients in clinical practice, motor slowness needs to be taken into account.
Highlights
IntroductionMotor slowness (bradykinesia) is a core feature of Parkinson’s disease (PD). It is often assumed that patients show mental slowness (bradyphrenia) as well; evidence for this is debated
Motor slowness is a core feature of Parkinson’s disease (PD)
For the other neuropsychological tests, neither the combination of motor time (MT) and reaction time (RT) nor MT or RT separately were significant predictors of PD patients’ performances; the results of complete models were as follows: attention [Stroop Word Card: R2 = .09, F(2, 54) = 2.67, p = .079], memory [Digit Span Forward: R2 = .05, F(2, 54) = 1.24, p = .298; Rey Auditory Verbal Learning Test (RAVLT) immediate recall (IR): R2 = .07, F(2, 54) = 2.00, p = .146; RAVLT delayed recall (DR): R2 = .02, F(2, 54) = 0.52, p = .597], and executive functions (EF) [Trail Making Test Part A (TMT) B/A ratio: R2 = .02, F(2, 54) = 0.64, p = .532; Visual Elevator: R2 = .04, F(2, 51) = 1.12, p = .335; Zoo Map total score: R2 = .03, F(2, 54) = 0.82, p = .444]. This is the first study that measures RT and MT separately in order to determine whether mental slowness can be differentiated from motor slowness in patients with Parkinson’s disease
Summary
Motor slowness (bradykinesia) is a core feature of Parkinson’s disease (PD). It is often assumed that patients show mental slowness (bradyphrenia) as well; evidence for this is debated. The aims of this study were to determine whether PD patients show mental slowness apart from motor slowness and, if this is the case, to what extent this affects their performance on neuropsychological tests of attention, memory, and executive functions (EF). Method: Fifty-five nondemented PD patients and 65 healthy controls were assessed with a simple information-processing task in which reaction and motor times could be separated. Results: While PD patients showed significantly longer reaction times than healthy controls, their motor times were not significantly longer. Predict patients’ test performance, while motor times were found to have a significant negative influence on tests of attention. Neuropsychological test performance is not influenced by mental slowness; motor slowness can have a negative impact. When interpreting neuropsychological test performance of PD patients in clinical practice, motor slowness needs to be taken into account
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