Transcranial direct current stimulation (tDCS) is a non-invasive, painless brain stimulation technique that utilizes electrical currents to modulate the activity of neurons. A low intensity current is administered by electrodes to a specific part of the brain through the scalp to increase or decrease neuronal activity.

Despite the fact that tDCS dates back to the 1960s, tDCS has only recently been embraced and explored; over half the scientific articles on the technique have been published in the last two years. tDCS has been used to examine a variety of psychological conditions like anxiety, depression, Alzheimer’s disease, strokes, and chronic pain, but the method’s clinical efficacy is still largely inconclusive. Literature reviews and meta analyses are most helpful in teasing apart all the conflicting data, and there are some promising applications emerging for tDCS as a cognitive enhancement technique.

By strengthening or weakening neural connections, tDCS may facilitate memory formation and learning, as well as the neural plasticity necessary in stroke recovery. tDCS has been used to enhance treatment efficacy in post-stroke aphasia rehabilitation. The results seem promising, with tDCS being effective in increasing various language skills such as verbal speed, fluency, and amount of verbal learning. Language enhancement can also be applied to a word reading context. Repeated tDCS application to adults with developmental dyslexia has been shown to significantly improve reading speed and fluency.

Different studies have demonstrated an improvement in working memory and episodic memory in healthy subjects, with an increase in accuracy and in response time. These memory enhancement effects could be quite useful in combating the effects of both Alzheimer’s and Parkinson’s disease.

Previous research has shown that tDCS can also improve skills such as mathematical ability when applied to the dorsolateral prefrontal cortex, an area involved in regulating emotion. Additionally, innovative social cognition studies are finding reduced racial bias and prejudice after tDCS stimulation, providing an optimistic avenue to explore within the future of cognitive psychology.

It is important to note that upon review, the effects of a single tDCS session did not have a significant long-term effect on various cognitive functions. However, this could just mean that the technique would be more effective after multiple sessions.

As scientists and informed citizens with any burgeoning technology we must analyze new studies with a critical eye to truly understand the effectiveness and validity of their results. Nevertheless, given its simplicity and the volume of research being conducted on tDCS, it seems likely that it may become a generalized clinical tool in the near future; potentially providing therapeutic relief and cognitive enhancement to many people worldwide.

References
Bennabi, D., Pedron, S., Haffen, E., Monnin, J., Peterschmitt, Y., & Waes, V. (2014). Transcranial direct current stimulation for memory enhancement: From clinical research to animal models. Frontiers in Systems Neuroscience, 8.
Kadosh, R., Soskic, S., Iuculano, T., Kanai, R., & Walsh, V. (2010). Modulating Neuronal Activity Produces Specific And Long-Lasting Changes In Numerical Competence. Current Biology, 20(22), 2016-2020.
Horvath, J., Forte, J., & Carter, O. (2015). Quantitative Review Finds No Evidence of Cognitive Effects in Healthy Populations From Single-session Transcranial Direct Current Stimulation (tDCS). Brain Stimulation.
Heth, I., & Lavidor, M. (2015). Improved reading measures in adults with dyslexia following transcranial direct current stimulation treatment. Neuropsychologia, 70, 107-113.
Sellaro, R., Derks, B., Nitsche, M., Hommel, B., van den Wildenberg, W.P.M., van Dam, K., & Colzato, L.S. (submitted). Reducing prejudice through brain stimulation.