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

Abstract

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.

Non-invasive Brain Stimulation in the Treatment of Post-stroke and Neurodegenerative Aphasia: Parallels, Differences, and Lessons Learned

“…They found that in both stimulation conditions word retrieval greatly improved (Meinzer et al, 2014). Other studies employing a bilateral stimulation approach support Meinzer, demonstrating that ctDCS to the right hemisphere Brodmann area 44/45 and anodal stimulation to left Brodmann 44/45 results in improved language performance (Costa et al, 2015). …”

“…Integrating the first and second model, there is growing body of evidence supporting bi-hemispheric stimulation, wherein patients receive anodal tDCS to the left hemisphere and cathodal tDCS to the right hemisphere (Lee et al, 2013; Marangolo et al, 2014; Meinzer et al, 2014; Costa et al, 2015). Meinzer and colleagues conducted a study that contrasted the effect of anodal tDCS, dual hemisphere tDCS, and sham.…”

Use of Computational Modeling to Inform tDCS Electrode Montages for the Promotion of Language Recovery in Post-stroke Aphasia

“…The rationale for implementing bilateral tDCS was based on the assumption that simultaneously upregulating excitability of the intact portion of the ipsilesional hemisphere through anodic stimulation while at the same time downregulating excitability of the contralesional hemisphere through cathodic stimulation should lead to the greatest recovery. This has been demonstrated in the motor domain by Lindenberg et al [29] but has also recently been implemented in aphasia tDCS rehabilitation-research studies [30][31][32][33][34]. However, a major misconception in most of the aphasia unilateral bipolar 1x1 tDCS studies was that the focus and interest has been on the active electrode and researchers have neglected the role of the "return" electrode, assuming that, since the prefrontal cortex is not critically involved in language processing, the supraorbital electrode would be irrelevant with respect to the underlying area.…”

“…Indeed, bilateral tDCS studies in the motor domain have already shown that the simultaneous modulation of the left and right motor area with opposite current is effective for motor recovery [29]. In the language domain, initial studies both in single cases [30,34] and in patient groups [29,30,33] have already confirmed bilateral tDCS efficacy for promoting language recovery which was not limited to treated forms [30] but also generalized to untrained items [32].…”

“…While these five initial bilateral tDCS aphasia studies [229,30,[32][33][34] are an exciting first step into extending our understanding of tDCS dose and administration parameters for speechlanguage deficits post-stroke, more tDCS studies with a larger sample of subjects are needed in order to design optimal electrotherapies as an adjuvant for language recovery in stroke survivors with aphasia. …”