Bilateral Bi-Cephalic Tdcs with Two Active Electrodes of the Same Polarity Modulates Bilateral Cognitive Processes Differentially

Abstract

Transcranial direct current stimulation (tDCS) is an innovative method to explore the causal structure-function relationship of brain areas. We investigated the specificity of bilateral bi-cephalic tDCS with two active electrodes of the same polarity (e.g., cathodal on both hemispheres) applied to intraparietal cortices bilaterally using a combined between- and within-task approach. Regarding between-task specificity, we observed that bilateral bi-cephalic tDCS affected a numerical (mental addition) but not a control task (colour word Stroop), indicating a specific influence of tDCS on numerical but not on domain general cognitive processes associated with the bilateral IPS. In particular, the numerical effect of distractor distance was more pronounced under cathodal than under anodal stimulation. Moreover, with respect to within-task specificity we only found the numerical distractor distance effect in mental addition to be modulated by direct current stimulation, whereas the effect of target identity was not affected. This implies a differential influence of bilateral bi-cephalic tDCS on the recruitment of different processing components within the same task (number magnitude processing vs. recognition of familiarity). In sum, this first successful application of bilateral bi-cephalic tDCS with two active electrodes of the same polarity in numerical cognition research corroborates the specific proposition of the Triple Code Model that number magnitude information is represented bilaterally in the intraparietal cortices.

What letters can “learn” from Arabic digits – fMRI-controlled single case therapy study of peripheral agraphia

“…In particular, its crucial role during handwriting is still unclear, because: (i) language organisation in the brain shows high intra-individual variability (Lubrano, Roux, & Démonet, 2004); (ii) pure lesion data have the potential to provide causal structurefunctional relationships; but only, when combined with functional imaging one can identify, which parts of the frequently larger structural lesions in some patients are still functionally active as compared to other patients with similar pathology or whether other areas may be involved compensating lost functions due to functional reorganisation in chronic patients; (iii) although functional imaging studies are informative regarding potential areas functionally involved in writing, they do not provide causal structure-functional relationships but only correlations. The observed brain activity could also reflect unspecific co-activation of the respective cortex areas (Klein et al, 2013). Thus, drawing general conclusions regarding the role of Exner's area requires further research.…”

Double dissociation of working memory and attentional processes in smokers and non-smokers with and without nicotine

“…Non-smokers did not profit from nicotine and displayed slowed reaction times for all sections (word, color, and color-word) after nicotine patch administration. The Stroop task can be employed as a Bmarker^for an unspecific excitatory/inhibitory upregulation and downregulation of cognitive processes (Klein et al 2013). Similar to working memory performance, Stroop interference improves with increased cortical excitation, especially of the dorsolateral prefrontal cortex (Adleman et al 2002).…”

Cognitive Enhancement of Numerical and Arithmetic Capabilities: a Mini-Review of Available Transcranial Electric Stimulation Studies

“…In other words, higher demands not only for discriminating close targets but also for processing multidigit numbers could encompass more task-induced activity ready for neuromodulation. NDE in multi-digit comparisons was unaffected by several tDCS configurations of Hauser et al (2013), but the distractor-distance effect for selecting correct two-digit addition results was monotonically modulated by a bilateral-bicephalic parietal stimulation (Klein et al 2013). In contrast to the effect of tDCS on the parietal lobe, when the prefrontal cortex was stimulated, both NDE and single-digit accuracy rates were unaffected.…”

“…According to physical arrangement classification (Nasseri et al 2015), successful modulations of numerical performance utilized unilateral monopolar placements with large return electrodes, bilateral bipolar-balanced and non-balanced placements, as well as the dual-channel bilateral double-monopolar arrangement by Klein et al (2013). Most studies focus on parietal placements with 1 mA, but also prefrontal placements appear effective with tRNS (Pasqualotto 2016) and produce significant modulations of spatial-numerical associations (Schroeder et al 2016) and of math-related emotional processing (Sarkar et al 2014;Plewnia et al 2015).…”