Improvement of the Working Memory by Transcranial Direct Current Stimulation in Healthy Older Adults

Objective To investigate the short term effects of prefrontal transcranial direct current stimulation (tDCS) in healthy older adults aged more than 65 years by means of verbal and visuospatial working memory tasks. Method Twenty four healthy older adults (14 males and 10 females, age range: 65-78 years old) were enrolled in this study. A double-blind study was conducted. The subjects underwent sham or anodal tDCS over the left prefrontal cortex (F3 in the international 10-20 EEG system). DC was delivered for 30 minutes at 2 mA with 25 cm(2) saline-soaked sponge electrodes. A cathode electrode was applied to the left arm. Before and after tDCS, the subjects performed 2-back verbal working memory and visuospatial memory tasks. The rates of improvement of the accuracy and the reaction time were analyzed. Results On the 2-back verbal working memory tasks, the verbal working memory accuracy was improved in the real group compared with that of the sham group. On visuospatial working memory task, the working memory accuracy and reaction time were not improved in either the real group or the sham group. Conclusion The results showed beneficial effects of noninvasive anodal tDCS on the cognitive function in healthy older adults. We suggest that tDCS induces functional changes on the left prefrontal cortex, and it improves the age-related cognitive impairment in the healthy elderly population.