Transcranial Direct Current Stimulation (tDCS) of Left Parietal Cortex Facilitates Gesture Processing in Healthy Subjects

Abstract

Gesture processing deficits constitute a key symptom of apraxia, a disorder of motor cognition frequently observed after left-hemispheric stroke. The clinical relevance of apraxia stands in stark contrast to the paucity of therapeutic options available. Transcranial direct current stimulation (tDCS) is a promising tool for modulating disturbed network function after stroke. Here, we investigate the effect of parietal tDCS on gesture processing in healthy human subjects. Neuropsychological and imaging studies suggest that the imitation and matching of hand gestures involve the left inferior parietal lobe (IPL). Using neuronavigation based on cytoarchitectonically defined anatomical probability maps, tDCS was applied over left IPL-areas PF, PFm, or PG in healthy participants (n ϭ 26). Before and after tDCS, subjects performed a gesture matching task and a person discrimination task for control. Changes in error rates and reaction times were analyzed for the effects of anodal and cathodal tDCS (compared with sham tDCS). Matching of hand gestures was specifically facilitated by anodal tDCS applied over the cytoarchitectonically defined IPL-area PFm, whereas tDCS over IPL-areas PF and PG did not elucidate significant effects. Taking into account tDCS electrode size and the central position of area PFm within IPL, it can be assumed that the observed effect is rather the result of a combined stimulation of the supramarginal and angular gyrus than an isolated PFm stimulation. Our data confirm the pivotal role of the left IPL in gesture processing. Furthermore, anatomically guided tDCS of the left IPL may constitute a promising approach to neurorehabilitation of apraxic patients with gesture processing deficits.

Repetitive transcranial magnetic stimulation reveals a role for the left inferior parietal lobule in matching observed kinematics during imitation

“…Interestingly, a previous study by Weiss et al . () using transcranial direct current stimulation (tDCS) found that anodal stimulation over left area PFm improved participants’ gesture matching ability. However, the authors suggested that their result could have been driven by a combined effect of SMG and AG stimulation, considering the central position of PFm and the size of tDCS electrodes.…”

“…Weiss et al . () stated that both parts of the IPL may have to be stimulated simultaneously in order to facilitate gesture matching. Considering our results, the same could be true for influencing gesture imitation and further highlights the importance of considering in detail the role of different regions of the IPL, along with their interactions.…”

“…An alternative explanation for the similar effects observed for both stimulation sites is that our results reflect an influence of unspecified peripheral stimulation of another area of the IPL, for example cytoarchitectonic area PFm, which lies between PF (in the SMG) and PGa (AG). Interestingly, a previous study by Weiss et al (2013) using transcranial direct current stimulation (tDCS) found that anodal stimulation over left area PFm improved participants' gesture matching ability. However, the authors suggested that their result could have been driven by a combined effect of SMG and AG stimulation, considering the central position of PFm and the size of tDCS electrodes.…”

“…However, the authors suggested that their result could have been driven by a combined effect of SMG and AG stimulation, considering the central position of PFm and the size of tDCS electrodes. Weiss et al (2013) stated that both parts of the IPL may have to be stimulated simultaneously in order to facilitate gesture matching. Considering our results, the same could be true for influencing gesture imitation and further highlights the importance of considering in detail the role of different regions of the IPL, along with their interactions.…”

Single-Session Anodal tDCS with Small-Size Stimulating Electrodes Over Frontoparietal Superficial Sites Does Not Affect Motor Sequence Learning

“…Finding novel techniques to improve rehabilitation in fine movements in the trained hand as well as transfer of learning into the untrained hand would implicate for patients who struggle with fine motor tasks, such as those with stroke or Parkinson’s disease. Recently, anodal transcranial direct current stimulation (a-tDCS), which modulate brain activity, has allowed direct investigation of the role of specific areas of the brain during different stages of sequence learning (Nitsche et al, 2003; Fregni et al, 2005; Reis et al, 2009; Schambra et al, 2011; Zaehle et al, 2011; Javadi and Walsh, 2012; Pope and Miall, 2012; Hoy et al, 2013; Saucedo Marquez et al, 2013; Weiss et al, 2013; Convento et al, 2014; Waters-Metenier et al, 2014; Reis et al, 2015; Rivera-Urbina et al, 2015). …”