Dual Transcranial Direct Current Stimulation Research Articles

Ipsilesional and contralesional regions participate in the improvement of poststroke aphasia: a transcranial direct current stimulation study

In the past few years, noninvasive cerebral stimulations have been used to modulate language task performance in healthy and aphasic patients. In this study, a dual transcranial direct current stimulation (tDCS) on anterior and posterior language areas was applied for 2 weeks to a patient with a possible crossed aphasia following a right hemisphere stroke. Inhibitory cathodal stimulation of the right Brodmann areas (BA) 44/45 and simultaneous anodal stimulation of the left BA 44/45 improved the patient’s performance in picture naming. Conversely, the same bilateral montage on BA 39/40 did not produce any significant improvement; finally, electrode polarity inversion over BA 39/40 yielded a further improvement compared with the first anterior stimulation. Our findings suggest that ipsilesional and contralesional areas could be useful in poststroke functional reorganization and provide new evidences for the therapeutic value of tDCS in aphasia.

Enhanced Motor Learning Following Task-Concurrent Dual Transcranial Direct Current Stimulation

ObjectiveTranscranial direct current stimulation (tDCS) of the primary motor cortex (M1) has beneficial effects on motor performance and motor learning in healthy subjects and is emerging as a promising tool for motor neurorehabilitation. Applying tDCS concurrently with a motor task has recently been found to be more effective than applying stimulation before the motor task. This study extends this finding to examine whether such task-concurrent stimulation further enhances motor learning on a dual M1 montage. MethodTwenty healthy, right-handed subjects received anodal tDCS to the right M1, dual tDCS (anodal current over right M1 and cathodal over left M1) and sham tDCS in a repeated-measures design. Stimulation was applied for 10 mins at 1.5 mA during an explicit motor learning task. Response times (RT) and accuracy were measured at baseline, during, directly after and 15 mins after stimulation. Motor cortical excitability was recorded from both hemispheres before and after stimulation using single-pulse transcranial magnetic stimulation. ResultsTask-concurrent stimulation with a dual M1 montage significantly reduced RTs by 23% as early as with the onset of stimulation (p<0.01) with this effect increasing to 30% at the final measurement. Polarity-specific changes in cortical excitability were observed with MEPs significantly reduced by 12% in the left M1 and increased by 69% in the right M1. ConclusionPerformance improvement occurred earliest in the dual M1 condition with a stable and lasting effect. Unilateral anodal stimulation resulted only in trendwise improvement when compared to sham. Therefore, task-concurrent dual M1 stimulation is most suited for obtaining the desired neuromodulatory effects of tDCS in explicit motor learning.

Effects of dual transcranial direct current stimulation on post-stroke unilateral visuospatial neglect

Based on the interhemispheric inhibition model of unilateral visuospatial neglect (USN) after stroke, the effects of dual-mode transcranial direct current stimulation (tDCS) over the parietal cortices were assessed in a double-blind random-order cross-over experiment. Ten chronic right hemispheric stroke patients (4 men; mean age: 62.6 years) with USN were recruited. All participants underwent three randomly arranged tDCS sessions: (1) dual-mode, anodal tDCS over the right posterior parietal cortex (PPC) and cathodal tDCS over the left PPC; (2) single-mode, anodal tDCS over the right PPC; and (3) sham mode. Each session lasted 20min. Before and immediately after the stimulation, a line bisection test and star cancelation test were carried out. In the line bisection test, significant improvements were observed after both the dual- and the single-mode tDCS (p<0.05), but not after sham stimulation. Statistical analysis showed a significant interaction between time and tDCS mode, where the dual tDCS had a stronger effect than the single or sham stimulation modes (p<0.05). The star cancelation test did not show any significant change. These results suggest that dual tDCS over the bilateral PPC is an effective method for the treatment of USN in stroke patients.

Effects of Dual Transcranial Direct Current Stimulation for Aphasia in Chronic Stroke Patients

ObjectiveTo investigate any additional effect of dual transcranial direct current stimulation (tDCS) compared with single tDCS in chronic stroke patients with aphasia.MethodsEleven chronic stroke patients (aged 52.6±13.4 years, nine men) with aphasia were enrolled. Single anodal tDCS was applied over the left inferior frontal gyrus (IFG) and a cathodal electrode was placed over the left buccinator muscle. Dual tDCS was applied as follows: 1) anodal tDCS over the left IFG and cathodal tDCS over the left buccinator muscle and 2) cathodal tDCS over the right IFG and anodal tDCS over the right buccinator muscle. Each tDCS was delivered for 30 minutes at a 2-mA intensity. Speech therapy was provided during the last 15 minutes of the tDCS. Before and after the stimulation, the Korean-Boston Naming Test and a verbal fluency test were performed.ResultsThe dual tDCS produced a significant improvement in the response time for the Korean-Boston Naming Test compared with the baseline assessment, with a significant interaction between the time and type of interventions. Both single and dual tDCS produced a significant improvement in the number of correct responses after stimulation with no significant interaction. No significant changes in the verbal fluency test were observed after single or dual tDCS.ConclusionThe results conveyed that dual tDCS using anodal tDCS over the left IFG and cathodal tDCS over the right IFG may be more effective than a single anodal tDCS over the left IFG.