Onsite-effects of dual-hemisphere versus conventional single-hemisphere transcranial direct current stimulation: A functional MRI study

Abstract

We performed functional MRI examinations in six right-handed healthy subjects. During functional MRI scanning, transcranial direct current stimulation was delivered with the anode over the right primary sensorimotor cortex and the cathode over the left primary sensorimotor cortex using dual-hemispheric transcranial direct current stimulation. This was compared to a cathode over the left supraorbital area using conventional single-hemispheric transcranial direct current stimulation. Voxel counts and blood oxygenation level-dependent signal intensities in the right primary sensorimotor cortex regions were estimated and compared between the two transcranial direct current stimulation conditions. Our results showed that dual-hemispheric transcranial direct current stimulation induced greater cortical activities than single-hemispheric transcranial direct current stimulation. These findings suggest that dual-hemispheric transcranial direct current stimulation may provide more effective cortical stimulation than single-hemispheric transcranial direct current stimulation.

Keywords: cortical activation; dual-hemispheric stimulation; functional MRI; neural regeneration; neuroimaging; primary sensorimotor cortex; regeneration; transcranial direct current stimulation.

Figure 1

The schema of the experimental design and transcranial direct current stimulation (tDCS) application. The functional MRI (fMRI) scanning was performed as a block design with a sham-resting phase, preparatory phase, and a stimulation phase. All subjects underwent conditions A and B with a 5-minute rest period between the conditions to allow for the elimination of the effects of the previous tDCS. The orders of the conditions were evenly counterbalanced in each of subjects to control for order effects in a repeated measures design. For the dual-hemispheric tDCS, the anodal electrode was placed over the primary sensorimoter cortex (SM1) in the right hemisphere, whereas the cathodal electrode was placed over the SM1 in the left hemisphere. For conventional single-hemispheric tDCS, the anodal electrode was placed over the SM1 in the left hemisphere, whereas the cathodal electrode was placed over the supraorbital area in the right hemisphere.