Front. Hum. Neurosci., 19 June 2020 | https://doi.org/10.3389/fnhum.2020.00235
- Cognitive NeuroLab, Faculty of Health Sciences, Universitat Oberta de Catalunya (UOC), Barcelona, Spain
Transcranial magnetic stimulation (TMS) is a non-invasive brain stimulation technique able to modulate cortical excitability. This modulation may influence areas and networks responsible for specific cognitive processes, and the repetition of the induced temporary changes can produce long-lasting effects. TMS effectiveness may be enhanced when used in conjunction with cognitive training focused on specific cognitive functions. Playing video games can be an optimal cognitive training since it involves different cognitive components and high levels of engagement and motivation. The goal of this study is to assess the synergistic effects of TMS and video game training to enhance cognition, specifically, working memory and executive functions. We conducted a randomized 2 × 3 repeated measures (stimulation × time) study, randomly assigning 27 healthy volunteers to an active intermittent theta-burst stimulation or a sham stimulation group. Participants were assessed using a comprehensive neuropsychological battery before, immediately after, and 15 days after finishing the video game+TMS training. The training consisted of 10 sessions where participants played a 3D platform video game for 1.5 h. After each gaming session, TMS was applied over the right dorsolateral prefrontal cortex (DLPFC). All participants improved their video gaming performance, but we did not find a synergistic effect of stimulation and video game training. Neither had we found cognitive improvements related to the stimulation. We explored possible confounding variables such as age, gender, and early video gaming experience through linear regression. The early video gaming experience was related to improvements in working memory and inhibitory control. This result, although exploratory, highlights the influence of individual variables and previous experiences on brain plasticity.
Non-invasive brain stimulation techniques have become a step forward in cognitive neuroscience due to their ability to establish causal links between cognition and its neural substrate. Among these techniques, transcranial magnetic stimulation (TMS) allows modulation of cortical excitability in highly specific target regions, inducing changes in the associated cognitive functions and even enhancing them (e.g., Luber and Lisanby, 2014).
Nevertheless, the specific parameters through which TMS affects cognition are not entirely clear. TMS effectiveness seems to be partially task-dependent (Koch and Rothwell, 2009; Johnson et al., 2012; Duecker et al., 2013; Matsugi et al., 2014) and most effective when used together with cognitive training (Bentwich et al., 2011; Schilberg et al., 2012; Hopfner et al., 2015; Rabey and Dobronevsky, 2016; Lee et al., 2017; Nguyen et al., 2017). But both, the stimulation and the training must have certain characteristics to achieve the desired near-transfer and far-transfer effects (i.e., translation of benefits to similar or different cognitive domains, respectively).
Regarding the stimulation, its influence can be maximized when it is delivered after skill training. This allows us to take advantage of the state-dependency effects in specific neural populations (Romei et al., 2016), and TMS can interact with their current, imbalanced state (Silvanto et al., 2018). Examples in animal studies, using hypothalamic intracranial self-stimulation have shown that, administering the stimulation immediately after a skill training produce higher retention rates for that skill than administering the stimulation before the training (Redolar-Ripoll et al., 2002).
On the other hand, transfer effects of the training are maximized when different cognitive skills are integrated (Taatgen, 2013), high levels of engagement and motivation are maintained (Maraver et al., 2016), and there is sufficient exposure to the task (Zhao et al., 2020). In recent decades, video games have received a great deal of attention as cognitive training tools, due to some features that make them suitable for cognitive enhancement: they are widely available, integrate several cognitive processes at once, allow adjustment of variable difficulty, and are highly motivating and engaging. Furthermore, they are often used for long enough over a person’s lifetime to have a real impact on cognition. There is a considerable body of literature dedicated to the effects of video gaming on the brain (for a systematic review see Palaus et al., 2017), and the implications of using a particular video game genres are well understood (Dobrowolski et al., 2015).
Given the ability of TMS to induce plastic changes in the brain, and the particular suitability of video games to train cognitive functions, we expect that their combination would produce synergistic effects on cognitive enhancement, but the literature documenting combined use of TMS and video games is still scarce (e.g., Anguera et al., 2013). In particular, we expect to enhance cognition (i.e., processing speed, visuospatial skills, attention, working memory, executive functions, and general intelligence) in a healthy sample by playing a 3D platform video game during 10 sessions and applying TMS over the dorsolateral prefrontal cortex (DLPFC) immediately after playing. We hypothesized that post video game TMS would enhance the positive effects of video game training over cognition.