Neurocognitive Effects of Transcranial Direct Current Stimulation in Arithmetic Learning and Performance: A Simultaneous tDCS-fMRI Study

Abstract

BACKGROUND A small but increasing number of studies suggest that non-invasive brain stimulation by means of transcranial direct current stimulation (tDCS) can modulate arithmetic processes that are essential for higher-order mathematical skills and that are impaired in dyscalculic individuals. However, little is known about the neural mechanisms underlying such stimulation effects, and whether they are specific to cognitive processes involved in different arithmetic tasks. METHODS We addressed these questions by applying tDCS during simultaneous functional magnetic resonance imaging (fMRI) while participants were solving two types of complex subtraction problems: repeated problems, relying on arithmetic fact learning and problem-solving by fact retrieval, and novel problems, requiring calculation procedures. Twenty participants receiving left parietal anodal plus right frontal cathodal stimulation were compared with 20 participants in a sham condition. RESULTS We found a strong cognitive and neural dissociation between repeated and novel problems. Repeated problems were solved more accurately and elicited increased activity in the bilateral angular gyri and medial plus lateral prefrontal cortices. Solving novel problems, in contrast, was accompanied by stronger activation in the bilateral intraparietal sulci and the dorsomedial prefrontal cortex. Most importantly, tDCS decreased the activation of the right inferior frontal cortex while solving novel (compared to repeated) problems, suggesting that the cathodal stimulation rendered this region unable to respond to the task-specific cognitive demand. CONCLUSIONS The present study revealed that tDCS during arithmetic problem-solving can modulate the neural activity in proximity to the electrodes specifically when the current demands lead to an engagement of this area.

Psychological and Brain Connectivity Changes Following Trauma-Focused CBT and EMDR Treatment in Single-Episode PTSD Patients

“…The present results, together with previously reported findings in PTSD patients, might suggest potential targets for both TMS and tES applications aimed at enhancing the therapeutic processes induced by psychotherapy. For instance, application of cathodal tDCS over the occipital lobe in PTSD patients might decrease local cortical excitability and modulate connectivity patterns (Callan et al, 2016; Hauser et al, 2016), and could be used to amplify the effect of each therapeutic session. Following the same logic, increase in excitability of prefrontal regions could be achieved by means of anodal tDCS, possibly increasing top-down control over subcortical regions.…”

Effects of Transcranial Direct Current Stimulation on Baseline and Slope of Prefrontal Cortex Hemodynamics During a Spatial Working Memory Task

“…In another study, tDCS paired with an n-back memory task reduced prefrontal oxygenated (HbO) and deoxygenated hemoglobin (HbR) (Choe et al, 2016). Yet, there is also evidence of increased alpha power (Choe et al, 2016), and BOLD response with anodal stimulation (Alekseichuk et al, 2016;Hauser et al, 2016).…”

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

“…Most studies employed supraorbital or prefrontal return cathodes without necessarily highlighting potential effects on such domain-general functions. Interestingly, for novel and complex subtractions, left parietal tDCS prevented characteristic prefrontal deactivations below the right prefrontal cathode as captured with simultaneous fMRI (Hauser et al 2016) and this configuration improved reaction times (Hauser et al 2013). In another paradigm, after viewing an instructional video, administering a complex statistical procedure was enhanced from left parietal anodal tDCS with a temporal cathode (Houser et al 2015), but not with placement of a prefrontal cathode (Houser et al 2014).…”