Effect of Anodal Transcranial Direct Current Stimulation at the Right Dorsolateral Prefrontal Cortex on the Cognitive Function in Patients With Mild Cognitive Impairment: A Randomized Double-Blind Controlled Trial

Abstract

ObjectivesTo study the effect of anodal transcranial direct stimulation (atDCS) of the right dorsolateral prefrontal cortex (DLPFC) on cognitive function and side effects in patients with mild cognitive impairment. DesignExperimental double-blind randomized, sham-controlled trial. SettingDepartment of Rehabilitation Medicine, King Chulalongkorn Memorial Hospital ParticipantsVolunteers (N=45) with mild cognitive impairment. InterventionsNot applicable. Main Outcome MeasuresThe atDCS group (n=23) were stimulated at 2 mA for 20 minutes with the anode on the right DLPFC and the cathode on the left supraorbital area. The control group (n=22) received placebo stimulation. Baseline cognitive function was assessed using the Cambridge Neuropsychological Test Automated Battery test. Participants were treated 3 times per week for 4 weeks (12 sessions). Cognitive function and side effects were assessed immediately after the first stimulation, the last session, and 4 weeks after treatment. ResultsCambridge Neuropsychological Test Automated Battery results revealed a significant improvement in the accuracy of the visual sustained attention (VSA) in the atDCS group at all 3 time points, the spatial working memory and visual memory (VM) immediately after the first stimulation, and a decreased VM reaction time after 12 sessions. A long-lasting effect on VSA and VM were found 4 weeks after treatment. ConclusionsAnodal tDCS over the right DLPFC enhanced the VSA, spatial working memory, and VM accuracy after the first stimulation and reduced the reaction time of VM after 12 sessions. A long-lasting effect on VSA and VM was found 4 weeks after treatment. This study corroborated atDCS as a safe technique to improve cognitive function.