Motor Speed Matters! Cognitive Profile of Parkinson's Disease Patients With and Without Deficits in Motor Speed.

Background: Parkinson's disease (PD) is characterized by bradykinesia, tremor, rigidity, postural instability and cognitive deficits in attention, executive functions, learning and memory. Motor speed, measured using Finger Tapping Test (FTT), is an important indicator and predictor of cognitive and motor functions. Deficits in motor speed have significant impact on performance on other neuropsychological tests. Objective: This study aimed to understand and compare the cognitive profile of patients with and without deficits in motor speed as evaluated on the FTT. Method and Material: A detailed neuropsychological evaluation using the NIMHANS Neuropsychological Battery was carried out on 70 PD patients. The PD patients were divided into patients with (n = 46) and without (n = 24) motor speed deficits. The two groups were comparable with regard to age (P = 0.591), years of formal education (up to 10th – 24.3, above 10th – 75.7) duration of illness (P = 0.703) and age of onset (P = 0.721). Results: Across the various cognitive domains such as executive functions, verbal recognition, visuospatial functions, visual learning and memory, the group without deficits in motor speed performed significantly better in comparison to patients with motor symptoms. Conclusion: A short and simple test such as FTT may be helpful in predicting the range and severity of cognitive deficits across other cognitive domains in patients with PD. Future studies on larger cohort examining the intricate role and association of FTT and other motor functions such as dexterity may be helpful in understanding the nature and severity of other cognitive functions in this clinical population.