Transcranial direct‐current stimulation enhances implicit motor sequence learning in persons with Parkinson's disease with mild cognitive impairment

Abstract

Implicit motor sequence learning (IMSL) is affected in Parkinson's disease (PD). Research in healthy young participants shows the potential for transcranial direct‐current stimulation (tDCS) over the primary motor cortex (M1) to enhance IMSL. In PD, only null effects have been reported to date. We determined concurrent, short‐term, and long‐term effects of anodal tDCS over M1 on IMSL, as measured by the serial reaction time (SRT) task, in persons with PD with mild cognitive impairment (MCI). Concurrent (anodal/sham tDCS intervention during the SRT task), short‐term (5 min post‐intervention), and long‐term (1 week post‐intervention) effects on IMSL were evaluated in persons with idiopathic PD (Hoehn and Yahr stage II‐III) with MCI. Results of 11 persons with PD (8 men and 3 women; mean age = 77.1 years; mean disease duration = 7.7 years) showed significant IMSL in the anodal (p = .016), but not in the sham tDCS condition (p = .937). Post‐hoc analyses showed that IMSL reached statistical significance at 1 week post‐intervention (p < .001). Anodal tDCS over M1 exerted beneficial effects on IMSL in persons with PD with MCI, in particular one week post‐intervention. Our study is the first to report a positive effect of tDCS on IMSL in PD. Further research should include a larger, more cognitively diverse sample and additional follow‐up periods.

Registered report: Does transcranial direct current stimulation of the primary motor cortex improve implicit motor sequence learning in Parkinson's disease?

“…Studies employing similar tDCS parameters have shown positive effects in healthy older adults (Zimerman et al, 2013) and, recently, in individuals with PD (Firouzi et al, 2020).…”

Transcranial Direct Current Stimulation (tDCS) as a Useful Rehabilitation Strategy to Improve Cognition in Patients With Alzheimer's Disease and Parkinson's Disease: An Updated Systematic Review of Randomized Controlled Trials

“…Two studies (64,65) were excluded because of different reasons (see Figure 1). Finally, 17 articles were included in our systematic review, 10 pertaining AD (12,20,(50)(51)(52)(53)(54)(55)(56)(57) and 7 pertaining PD (10,39,(58)(59)(60)(61)(62). The evaluation of methodological criteria used was first shown in Tables 1, 2.…”

“…Structural abnormalities of fronto-parietal areas and subcortical regions ( 37 ) and temporo-parietal regions ( 38 ) implicated in visual stimuli analysis have been observed in patients with PD, too. A particular impairment of implicit motor sequence learning (IMSL) is also displayed by patients with PD, consisting of difficulties in acquisition of multiple single movements to be performed in a sequential order without conscious awareness needed for retrieval ( 39 ).…”

Efficacy of Transcranial Direct Current Stimulation Over Dorsolateral Prefrontal Cortex in Patients With Minimally Conscious State

“…Several previous studies have demonstrated that the FC changes over time in the resting state were significantly correlated with the level of conscious state, which was often indexed by a subjective behavioral assessment, such as Coma Recovery Scale-Revised (CRS-R) (16,17). Even though some studies reported significant changes in FC caused by tDCS in stroke and Parkinson's disease, it is unclear to what extent the functional connectivity alterations would occur in MCS by administering tDCS (18,19).…”