Transcranial direct current stimulation increases resting state interhemispheric connectivity.

Transcranial direct current stimulation (tDCS) has been increasingly used to investigate human brain functions. Especially, tDCS on the dorsolateral prefrontal cortex (DLPFC) enhances cognitive functions in both healthy subjects and patients with neuropsychiatric disorders. In spite of its effects on behavioral improvement, neural correlates of tDCS on the DLPFC have not been fully described. In this study, we acquired resting state functional magnetic resonance imaging data before and after real or sham stimulation on the left DLPFC. Resting state functional connectivity of the stimulated brain region was compared between the two groups. Compared to the sham stimulation group, the tDCS group showed increased DLPFC connectivity to the right hemisphere and decreased DLPFC connectivity to the brain regions around the stimulation site in the left hemisphere. Application of tDCS on the DLPFC may induce increased interhemispheric connectivity even at rest, possibly associated with the behavioral effects of tDCS.