Cognitive Enhancement or Cognitive Cost: Trait-Specific Outcomes of Brain Stimulation in the Case of Mathematics Anxiety

Abstract

The surge in noninvasive brain stimulation studies investigating cognitive enhancement has neglected the effect of interindividual differences, such as traits, on stimulation outcomes. Using the case of mathematics anxiety in a sample of healthy human participants in a placebo-controlled, double-blind, crossover experiment, we show that identical transcranial direct current stimulation (tDCS) exerts opposite behavioral and physiological effects depending on individual trait levels. Mathematics anxiety is the negative emotional response elicited by numerical tasks, impairing mathematical achievement. tDCS was applied to the dorsolateral prefrontal cortex, a frequent target for modulating emotional regulation. It improved reaction times on simple arithmetic decisions and decreased cortisol concentrations (a biomarker of stress) in high mathematics anxiety individuals. In contrast, tDCS impaired reaction times for low mathematics anxiety individuals and prevented a decrease in cortisol concentration compared with sham stimulation. Both groups showed a tDCS-induced side effect-impaired executive control in a flanker task-a cognitive function subserved by the stimulated region. These behavioral and physiological double dissociations have implications for brain stimulation research by highlighting the role of individual traits in experimental findings. Brain stimulation clearly does not produce uniform benefits, even applied in the same configuration during the same tasks, but may interact with traits to produce markedly opposed outcomes.

Transcranial Electrical Stimulation as a Tool to Enhance Attention

“…One cannot meaningfully speak of enhancement when a substantial portion of individuals shows no response or even a detriment. Potential costs to cognitive enhancement are often overlooked, but are a real possibility: enhancement of one cognitive function could be paired with a decline in another function (Brem et al 2014a;Iuculano and Cohen Kadosh 2013;Sarkar et al 2014), as the brain networks underlying cognitive functions do not operate in isolation (Wokke et al 2015).…”

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

“…In the field of arithmetic, several studies have investigated the beneficial effect of tDCS on various aspects of arithmetic problem solving and learning [13,16,17,36]. However, despite first progress, the findings thus far are relatively heterogeneous and different stimulation protocols being beneficial only for a narrow set of cognitive processes and skills.…”

“…In the arithmetic domain, first studies have demonstrated that tDCS can affect arithmetic performance and learning [13][14][15][16]. However, the observed effects strongly depended on the cognitive processes involved in the arithmetic operation as well as the placement of the tDCS electrodes.…”

The modulating effects of brain stimulation on emotion regulation and decision-making

“…These studies show that, depending on the stimulated brain regions, anodal tDCS influences arousal during emotion regulation [20], regulation of negative emotions in situations characterized by social exclusion [63,64], mathematics anxiety [67], emotional reactions to pain stimuli [62], negative affect for negative pictures [59], negative affect for negative stimuli [56], and momentary ruminative self-referent thoughts [76].…”

“…In a study on mathematics anxiety in healthy subjects using tDCS and salivary cortisol, Sarkar et al [67] expected that anodal stimulation to the left DLPFC and inhibitory cathodal stimulation to the right DLPFC would produce the greatest reduction in negative emotional reactions. The authors based this on previous studies related to salivary cortisol [8] and positive and negative emotional processing of the left and right DLPFC ( [31,78].…”