# Integration Between Serious Games and EEG Signals:
## 4 A Review of Technological Solutions That Integrate Serious Game and EEG Signals
### Experimental Strategy Based on Spontaneous Signals  
In this strategy, the user performs a mental task such as imagined movement, counting, or subvocal counting to create changes in brain signals that can be detected by a BCI [56]. Therefore, spontaneous signals are generated by the subject voluntarily without any external stimulus. [PERSON] et al. [51] presented the design, algorithm, and implementation of two new EEG-based 2D and 3D concentration games using a fractal dimension model. The experiment was designed to be able to classify two brain states (relaxation and concentration). [PERSON] et al. [64] proposed a video game that allows multiple users to connect to the same application in a 3D environment controlled by the characteristics of EEG. In this work, EEG signals were related to three different levels of attention and traditional control mechanisms such as the keyboard. The authors identified that the main motor rhythms in EEG connected to attention and memory correspond to the theta (4-8 Hz), alpha (8-12 Hz), and beta (13-20 Hz) bands of EEG. [PERSON] et al. [65] designed and developed a human-machine interface (HMI) to control a game based on the implementation of bio-signals. For this research (first phase), they decided to record brain signals and also use voice recognition as an additional tool for control. The \(\mu\) waves were analyzed because they are related to events that occur only during imaginary and real motor action, which have a frequency similar to \(\alpha\) waves. In addition, [PERSON] et al. [66] measured brain wave activation through an electroencephalogram to relate psychological components to physiological measurements. From the EEG signal recording in the experiment, which presents a psychological evaluation phase and a phase of playing video games, the activation of different band frequencies or waves emitted by the brain (theta, beta, alpha, and delta) was observed along with the area in which they are most active. [PERSON] and [PERSON] [68] created a serious game to measure and compare people's brain activity based on beta waves when playing a serious game in 2D and 3D (beta waves are activated just when the person is concentrating). [PERSON] et al. [69] examined the effect of gaming experience on the ability to modulate brain patterns during motor imagery training and the elements that contribute to high BCI control. For the experiment, users were grouped based on their gaming experience (experienced player and moderate player), and mental images of the corresponding hand (right or left) were used for game control. [PERSON] et al. [18] presented a proposal for an EEG-based serious game that provides training to increase focus for those diagnosed with Attention Deficit Hyperactivity Disorder (ADHD), and Attention Deficit Disorder (ADD). The research contemplated two states to be trained (\"push\" and \"neutral\") and the tests were performed on healthy subjects who did not suffer from ADHD symptoms, who used mentally issued commands (after training) to move the avatar. In the study by [PERSON] et al. [67], they also studied ADHD, exploring a multi-channel EEG-based BCI using regression and classification methods for attention training by a serious game.