Tetris is a worldwide falling block puzzle computer game that has attracted many people over three decades. Studies using Tetris have been conducted across various disciplines mainly in the field of behavioral and cognitive sciences (Haier et al. 1992a, b, 2009; De Lisi and Wolford 2002; Holmes et al. 2009, 2010; Rietschel et al. 2012; Belchior et al. 2013; Nouchi et al. 2013; Price et al. 2013; Yoshida et al. 2014; Harmat et al. 2015; Lindstedt and Gray 2015; Skorka-Brown et al. 2015; James et al. 2016; Sibert et al. 2016; Bikic et al. 2017; Iyadurai et al. 2017; Lau-Zhu et al. 2017; de Sampaio Barros et al. 2018; Meneghetti et al. 2018; Gold and Ciorciari 2019; Milani et al. 2019). Because visuospatial cognitive loads of Tetris are thought to compete with build-up of intrusive traumatic memories in the brain, recent studies have attempted to use Tetris for clinical application, in particular for prevention of traumatic flashbacks (Holmes et al. 2009, 2010; James et al. 2016; Iyadurai et al. 2017). Other studies looking at clinical applications of Tetris have demonstrated that this game may reduce drug cravings through competing visuospatial loads (Skorka-Brown et al. 2015). Overall, Tetris is expected to be used for cognitive training due to the cognitive effects associated with the game (e.g. improvement of attention, mental rotation and visuospatial working memory) (De Lisi and Wolford 2002; Belchior et al. 2013; Nouchi et al. 2013; Bikic et al. 2017; Milani et al. 2019). Important features of Tetris that make it suitable for clinical application include the fact that people of different cultures and with different cognitive levels are able to play Tetris with minimal instructions, having a high level of motivation and compliance because it is a worldwide entertainment game which can be conducted on various computer platforms non-verbally (it was certified in Guinness World Records as “most ported videogame” 1) (Ackerman 2016).
There are few studies investigating brain activity related to Tetris play (Haier et al. 1992a, b, 2009; Rietschel et al. 2012; Price et al. 2013; Yoshida et al. 2014; Harmat et al. 2015; de Sampaio Barros et al. 2018). Moreover, to our knowledge, canonical referential data of functional neuroimaging in healthy subjects during playing Tetris in a natural form has not been published yet. This would confirm Tetris’s neurocognitive clinical application based on evidence. Therefore, also as a potential preliminary step towards clinical application of Tetris, this study aimed to detect frontal activation patterns during playing Tetris using functional near-infrared spectroscopy (fNIRS), which has proven to be a reliable tool to explore cortical activation during the naturally performed Tetris game (Yoshida et al. 2014; Harmat et al. 2015; de Sampaio Barros et al. 2018).
fNIRS is a non-invasive neuroimaging technique, which requires little restriction compared with other neuroimaging methods such as positron emission tomography (PET), functional magnetic resonance imaging (fMRI) and magnetoencephalography (MEG). It shows low sensitivity to artifact by motion and electric devices. In addition, considering its high portability and low cost, the use of fNIRS is expected to spread worldwide (for a review see Pinti et al. 2018). In fNIRS, near-infrared light penetrates into tissues and is differentially absorbed by hemoglobin depending upon the oxygenation state and its optical path length in the tissues (modified Beer–Lambert Law). This relationship enables fNIRS to detect relative changes in concentration of oxygenated hemoglobin ([oxy-Hb]) and deoxygenated hemoglobin ([deoxy-Hb]) by emitting near-infrared light at several different wavelengths into the cortex and detecting its remnants (Jöbsis 1977; Hoshi 2003; Ferrari et al. 2004). Areas with high neural activity show increased oxygen consumption followed by supply oxygenated hemoglobin (neurovascular coupling) (Fox and Raichle 1986; Hoshi et al. 2001). This means that neural activity is measured indirectly by using relative changes in regional cerebral blood volumes (rCBV).
To our knowledge, there are three English articles using fNIRS during Tetris play (Yoshida et al. 2014; Harmat et al. 2015; de Sampaio Barros et al. 2018). However, these studies used Tetris to induce subjective flow experience without an interest of the underlying neural activation patterns of playing Tetris per se. Additionally, the extension of the cortex analyzed in those studies was much smaller than that of our study. The results of these previous studies suggest that the bilateral ventrolateral prefrontal cortex, the right dorsolateral prefrontal cortex (DLPFC) and the right inferior parietal lobe are significantly activated by Tetris play itself (de Sampaio Barros et al. 2018; Yoshida et al. 2014).
Using functional neuroimaging techniques, except for fNIRS, Tetris was first studied by Haier et al. (1992a), using PET in eight male healthy high performers trained intensively in Tetris. These subjects showed decreased metabolism over all brain areas induced by Tetris training. This led authors to conclude that activity of brain cortical areas was reduced by learning. They also reported that cortical metabolism after Tetris training could increase in areas needed for high Tetris performance, including the right precuneus and left cingulate (Haier et al. 1992b). Using fMRI Haier et al. (2009) demonstrated significant BOLD-signal increases in precentral gyrus, superior parietal lobule, inferior parietal lobule and occipital gyrus (after a 3-month training) during playing Tetris in 15 healthy females. In addition, cortical thickness increased in left superior frontal gyrus and anterior superior temporal gyrus after training Tetris. Another fMRI study showed significant BOLD-signal increases in the right occipital cortex and the left DLPFC during Tetris play (Price et al. 2013). However, in these functional neuroimaging studies, Tetris was performed under restricted experimental conditions. Thus, it is difficult to consider that cortical activation patterns were investigated during naturally-performed Tetris. Only an electroencephalography (EEG) study investigated neural activation and network activity during naturally-performed Tetris. In the study, the activations were measured on Fz, F3, F4, C3, C4, T3, T4, P3, P4, O1, and O2 of the international 10/20 system for EEG, and the network activities were investigated between Fz and the other measurement points. Its findings showed increasing activations across the cortical areas and elevated network activities between the motor planning area in the frontal cortex (Fz) and the other cortical areas (the sensory and executive brain regions) as difficulty of Tetris increases (Rietschel et al. 2012).
Based on the findings of previous Tetris studies, we hypothesized that significant activation would be found in the lateral prefrontal cortex. Furthermore, as an exploratory investigation we attempted to identify frontal areas required to play Tetris successfully taking into account the relation between activation and performance.