Transcranial electrical stimulation (TES) is a noninvasive form of brain stimulation which has been used to enhance cognitive performance. It may offer an alternative to pharmaceutical intervention in specific patient populations. The possibility of cognitive side effects has not been well-studied however. In this study, healthy human adults underwent cognitive training on a new numerical notation while receiving TES to the posterior parietal cortex or the dorsolateral prefrontal cortex. The posterior parietal cortex is a key brain area involved in numerical understanding while the dorsolateral prefrontal cortex is widely implicated in learning.
The results showed that stimulation of 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 enhancement of a specific cognitive ability can occur at the expense of other abilities. The authors suggest that this mental “cost” might be the result of a shift in metabolic consumption or neurochemical modulation caused by TES, which changes the respective involvement of different brain areas. These findings have important implications for the future development and use of enhancement technologies.
Iuculano T and Cohen Kadosh R: The mental cost of cognitive enhancement. J. Neuroscience 33(10): 4482-4486 (2013).
