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 cm² 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.

Objective
To investigate therapeutic effects of anodal direct current (DC) polarization on the primary motor cortex in subacute and chronic stroke patients by measuring changes of hand function and corticospinal excitability before and after stimulation. Method: Fourteen subacute and chronic stroke patients were included in this study. This study was designed as a sham-controlled, double-blind, and crossover experiment. The anode was positioned on the primary motor cortex of the affected hemisphere. The primary motor cortex was identified using transcranial magnetic stimulation (TMS), the motor evoked potentials (MEPs) were recorded by surface electrodes placed over the contralateral first dorsal interosseous muscle. DC was delivered for 20 minute at 2 mA with 25 cm² saline-soaked sponge electrodes. Before and after DC polarization, we checked the box and block test, nine hole peg test, grip power, lateral prehension power, MEPs amplitude, and MEPs latency. Results: The box and block test, grip power, lateral prehension power, and MEPs amplitude increased after anodal DC to primary motor cortex (p＜0.05). Positive correlation showed between improvement of box and block test and change of MEPs amplitude (r=0.808, p=0.001). Conclusion: Increased hand functions and the corticospinal tract excitability were obtained by 2 mA, 20 minute anodal DC polarization. Anodal DC polarization to primary motor cortex may play a potential role for facilitating the corticospinal tract thereby enhancing hand motor recovery in stroke patients. (J Korean Acad Rehab Med 2009; 33: 259-264)

Objective
To see whether anodal direct current (DC) polarization of the inferior parietal cortex (IPC) and the primary sensorimotor area (SM1) in corticobasal degeneration (CBD) patients leads to improvement of praxia and finger motion. Method: Twelve patients with CBD were enrolled. This single blind crossover study had three arms, anodal DC to IPC, anodal DC to SM1, and shame polarization on occipital area. DC was delivered for 40 minute at 2 mA with 25 cm2 sponge electrodes. Before and 20 min after the start of polarization, we performed the test of oral and limb apraxia (TOLA), finger tapping frequency, and grooved pegboard test. Results: The total score of TOLA was increased 5.4±2.3% after anodal DC to IPC. The scores of limb apraxia and picture gesture subtests of TOLA, not of oral apraxia subtest, increased significantly after anodal DC to IPC compared to sham DC polarization (p＜0.05). In anodal DC to SM1 group, the finger tapping frequency increased 15.5±14.1%, which was significantly greater than in sham group (p＜0.05). Conclusion: These results showed beneficial effects of anodal DC polarization on apraxia and hand function in CBD patients. In addition, these effects for apraxia and hand movement were dependent on their stimulation sites of brain. (J Korean Acad Rehab Med 2007; 31: 278-282)