Combining transcranial direct current stimulation with fMRI

Abstract

Anodal and cathodal transcranial direct current stimulations (tDCS) have been shown to have facilitatory and inhibitory effects over the motor and visual areas. In the present study we investigated the effects of repetitive anodal and cathodal tDCS on human brain activity and associated hemodynamics by concurrent blood-oxygenation-level-dependent (BOLD) functional magnetic resonance imaging at 3 Tesla. Neither anodal nor cathodal tDCS over the left primary motor cortex (M1) at 1 mA intensity for 20 seconds stimulation duration induced a detectable BOLD signal change. However, in comparison to a voluntary finger tapping task without stimulation, both anodal and cathodal tDCS during finger tapping inhibited the BOLD response in the supplementary motor area (SMA). Furthermore, cathodal stimulation resulted in a decrease in the BOLD response in the premotor cortex (PM), when combined with voluntary finger-tapping compared to without stimulation condition. These findings suggest that in contrast to the rest condition the combination of neuronal polarization and motor activation induces inhibitions in terms of both motor evoked potentials (Antal et al., 2007) and BOLD responses. Although the BOLD response is an indirect measure of neuronal activity, the combination of fMRI and concurrent tDCS may allow a more direct visualization of the electrical stimulation-induced changes in brain activity with high spatial resolution and the possibility to chart how tDCS modifies ongoing brain activations. Antal A, Terney D, Poreisz C, Paulus W (2007): Towards unravelling task-related modulations of neuroplastic changes induced in the human motor cortex. Eur J Neurosci 26:2687–91.