The Mental Cost of Cognitive Enhancement

Abstract

Noninvasive brain stimulation provides a potential tool for affecting brain functions in the typical and atypical brain and offers in several cases an alternative to pharmaceutical intervention. Some studies have suggested that transcranial electrical stimulation (TES), a form of noninvasive brain stimulation, can also be used to enhance cognitive performance. Critically, research so far has primarily focused on optimizing protocols for effective stimulation, or assessing potential physical side effects of TES while neglecting the possibility of cognitive side effects. We assessed this possibility by targeting the high-level cognitive abilities of learning and automaticity in the mathematical domain. Notably, learning and automaticity represent critical abilities for potential cognitive enhancement in typical and atypical populations. Over 6 d, healthy human adults underwent cognitive training on a new numerical notation while receiving TES to the posterior parietal cortex or the dorsolateral prefrontal cortex. Stimulation to the the posterior parietal cortex facilitated numerical learning, whereas automaticity for the learned material was impaired. In contrast, stimulation to the dorsolateral prefrontal cortex impaired the learning process, whereas automaticity for the learned material was enhanced. The observed double dissociation indicates that cognitive enhancement through TES can occur at the expense of other cognitive functions. These findings have important implications for the future use of enhancement technologies for neurointervention and performance improvement in healthy populations.

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).…”

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

“…In this paradigm, oppositional parietal tDCS (right anodal, left cathodal) produced faster automaticity and more linear mapping of artificial symbols in a training over 6 days, with sustainability after 6 months (Cohen Kadosh et al 2010). For the opposite placement, an impaired automaticity was detected, but here, the stimulation also produced steeper learning curves superior to prefrontal and sham stimulations (Iuculano and Cohen Kadosh 2013). Interestingly, when the numerical training paradigm was administered in two individuals with severe arithmetic problems, only the left anodal-right cathodal configuration, which led to impairment in typical participants, led to behavioral improvements (Iuculano and Cohen Kadosh 2014).…”

The Enhancement of Social Norm Compliance: Prospects and Caveats

“…Salient distractors caused interference in both placebo and methylphenidate conditions but significantly more in the methylphenidate condition compared with placebo, suggesting that methylphenidate enhanced attention to the target, but its effect was detrimental when stimulus features were shared by distractors and targets. Biases towards one behavior may be costly for flexible adaptation to the environment, and, more in general, for other cognitive functions, as it has been discussed in Iuculano and Kadosh (2013): findings show that numeric learning was enhanced by the transcranial electrical stimulation (TES) of the posterior parietal cortex and impaired by the TES of the dorsolateral prefrontal cortex, whereas the reverse was true for automaticity for learned material. This argument furthermore outlines a potential harmful consequence of uncontrolled long-term tDCS use (also see diytdcs.com), in addition to previously reported risks of adverse effects (Brunoni et al 2012).…”