Effects of transcranial direct current stimulation along with cognitive training on cognitive functions and activities of daily living in patients with Parkinson's disease: A pilot randomized controlled trial

Background: Cognitive impairment is one of the most common symptoms of Parkinson's disease (PD). In recent years, the effect of transcranial direct current stimulation (tDCS) have been investigated on various disabilities related to PD, including sensory and motor deficits and fatigue. Aim: To investigate effects of transcranial direct current stimulation (tDCS) along with cognitive training on attention, working memory, reaction time (RTI), response inhibition, and activities of daily living performance. Methods: This pilot randomized, single-blinded, and sham-controlled trial was performed on 32 people with PD who were blocked randomized equally into intervention and control groups. Intervention group received ten 20-min sessions of tDCS during ten 45-min sessions of cognitive training, while control group received ten 20-min sessions of sham-tDCS during ten 45-min sessions of cognitive training. Anodal electrode of tDCS (2 mA) was placed over left dorsolateral prefrontal cortex (DLPFC), while cathode was over right supraorbital region. A blinded assessor performed pretest, posttest, and follow-up assessments using the Unified Parkinson's Disease Rating Scale and four subtests of the CANTAB computer test including Match to Sample Visual Search, spatial span task, stop signal task, and RTI. Results: The results showed significant differences within groups over time in the mean scores of attention (F = 24.73, p = 0.00), working memory (F = 19.06, p = 0.000), RTI (F = 8.63, p = 0.005), response inhibition (F = 15.75, p = 0.000), and activity of daily living performance (F = 6.73, p = 0.013). ConclusiontDCS (anodal electrode over the left DLPFC and cathodal electrode over the right supraorbital region) along with cognitive training could facilitate improvement of cognitive functions and activities of daily living performance compared to routine cognitive exercises in people with PD.