Cognitive impartment is recurrent in Parkinson's disease (PD), including deficits in cognitive ability to learn, organize new information, form concepts, and switch focus between tasks (executive functions). These dysfunctions lead to gait alterations, because people with PD tend to prioritize only one activity in dual-task situations. Evidence shows that dual task treadmill training results in improved gait, postural balance, and motor coordination in PD. Transcranial direct current stimulation (tDCS) is a relevant tool in improving cognitive skills by modulating cortical excitability. However, there is a gap in the literature regarding the benefits of the association of these techniques when applied simultaneously in PD.

The study aimed to analyze the effects of tDCS simultaneous to dual-task treadmill training on motor function, functional mobility, verbal fluency, and processing speed in people with PD.

The pilot study of a double-blind, randomized controlled clinical trial including people with PD. People aged 40-70 years, above 24 in the Mini-Mental State Examination, and staging 1.5 to 3 of the modified Hoehn and Yahr scale were included. Eveluated for motor function (Unified Parkinson's Disease Rating Scale Part III - MDS-UPDRS, primary endpoint; Timed Up and Go - TUG test; Timed Up and Go dual task - TUG DT); and cognitive function (Stroop Test; Trail Making Test - TMT; Verbal Fluency Test - VF) before and after the 12 intervention sessions over four weeks. All received 2mA excitatory stimulation in the left dorsolateral prefrontal cortex for 20 minutes and treadmill gait training. The experimental group realized simultaneously a validated protocol for a randomized controlled trial of dual-task training, containing mental sorting, decision-making, and verbal fluency activities. We analyzed the normality of the sample by the Shapiro-Wilk test and the data by the Wilcoxon test, with a significance level of 95%.

Six subjects participated in the study, aged 60 (5.02) years; mixed clinical type (83%); MMSE score of 27.5 (1.71); H&Ymod of 2.08 (0.5); levodopa equivalent dose per day of 765.2 (399.3). They presented in the primary endpoint significant difference in motor function for MDS-UPDRS part III (Z=-2.060; p=0.039), in TUG functional mobility (Z=-1.992; p=0.046) and TUG DT (Z=-1992; p=0.046). As for cognitive function, there was no significant difference for the tests: Stroop (Z=-943; p=0.345); FV (Z=-1.761; p=0.078); and TMT (Z=-0.135; p=0.893).

The results suggest that the association between dual-task training and CBT affected motor function and functional mobility. Processing speed and verbal fluency showed no changes by dual-task training in the study.

The findings help explore methodologies and introduce new procedures to confirm the effects of the protocol under test.