Academic journal article Canadian Journal of Experimental Psychology

Transcranial Electrical Stimulation and Numerical Cognition

Academic journal article Canadian Journal of Experimental Psychology

Transcranial Electrical Stimulation and Numerical Cognition

Article excerpt

Processing, representing, and manipulating numbers and quantities is one of the most advanced cognitive abilities humans possess. This ability is becoming increasingly important with the rising dependence of society on technology, and rising educational and occupational focus on quantitative aptitude. Moreover, deficits in numerical cognition may impair both individual and societal achievement (Beddington et al., 2008; Duncan et al., 2007; Parsons & Bynner, 2005).

Recently, there has been increasing academic and public attention on the applications of transcranial electrical stimulation (tES) for cognitive enhancement. Improvements have been observed in a range of psychological variables in healthy populations, including high-level cognition such as visual short term memory (Tseng et al., 2012), working memory (Fregni et al., 2005; Richmond et al., 2014), planning (Dockery et al., 2009), language learning (Flöel et al., 2008; Meinzer et al., 2014), analogical reasoning (Santarnecchi et al., 2013), and numerical cognition. The application of tES to numerical cognition is the focus of this review.

Research on the use of tES for cognitive enhancement is very new, and within this emerging field, tES for enhancing numerical cognition is itself a nascent field of enquiry. The use of tES is both of scientific importance in understanding numerical cognition, and also of immense practical importance in the enhancement of typical and atypical numerical cognition. There are as yet no reviews on the use of tES for enhancing numerical cognition, though there are several on tES and general cognitive enhancement (e.g., Cohen Kadosh, 2013, in press; Jacobson, Koslowsky, & Lavidor, 2012; Krause & Cohen Kadosh, 2013; Kuo & Nitsche, 2012). An area of particular interest is the combination of tES and cognitive training, which seems to produce long-lived effects that are apparent even up to 6 months after the last stimulation session (e.g., Cappelletti et al., 2013; Cohen Kadosh et al., 2010; Looi et al., 2015; Reis et al., 2009; Snowball et al., 2013). Cognitive training leads to particular neuroanatomical and neurophysiological changes (Boyke et al., 2008; Draganski et al., 2004; Klingberg, 2010; Slagter et al., 2007). tES is combined with training to facilitate these neural changes, acting as an ingredient to sensitize the neural environment to the effects of training, thereby facilitating the acquisition of the practice effects to a greater degree than training by itself (Cohen Kadosh et al., 2012).

This article attempts to bring together several important findings in this (small) body of research to provide a general picture of this emerging field. The material is divided into three sections: (a) A short overview of two relevant forms of tES; (b) the application of tES in the enhancement of three aspects of numerical cognition: numerosity, magnitude processing, and arithmetic operations; and (c) an agenda for future research.

Principles of tES

The technology is portable, painless, easy to use, and safe when appropriate screening procedures are conducted (e.g., excluding participants with a personal or family history of epilepsy). The impact of the stimulation on neuronal activity depends on the shape of the current, and in this regard, there are several forms of tES that produce different effects based on the nature of the current. All the forms of tES can be accompanied by appropriate placebo conditions, in which the current is simply turned off after a brief period (e.g., 30 s), which serves as an effective placebo by generating physical sensations indistinguishable from real stimulation (Gandiga, Hummel, & Cohen, 2006), but no neural changes (Fritsch et al., 2010).

Two forms of tES have been used in numerical cognition research, transcranial direction current stimulation (tDCS), and transcranial random noise stimulation (tRNS), and some of their features are described below.

tDCS

This is the most well-known and most frequently used form of tES. …

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