  Current Motor Imagery Brain-Computer Interfaces (MI-BCI) require a lengthy
and monotonous training procedure to train both the system and the user.
Considering many users struggle with effective control of MI-BCI systems, a
more user-centered approach to training might help motivate users and
facilitate learning, alleviating inefficiency of the BCI system. With the
increase of BCI-controlled games, researchers have suggested using game
principles for BCI training, as games are naturally centered on the player.
This review identifies and evaluates the application of game design elements to
MI-BCI training, a process known as gamification. Through a systematic
literature search, we examined how MI-BCI training protocols have been gamified
and how specific game elements impacted the training outcomes. We identified 86
studies that employed gamified MI-BCI protocols in the past decade. The
prevalence and reported effects of individual game elements on user experience
and performance were extracted and synthesized. Results reveal that MI-BCI
training protocols are most often gamified by having users move an avatar in a
virtual environment that provides visual feedback. Furthermore, in these
virtual environments, users were provided with goals that guided their actions.
Using gamification, the reviewed protocols allowed users to reach effective
MI-BCI control, with studies reporting positive effects of four individual
elements on user performance and experience, namely: feedback, avatars,
assistance, and social interaction. Based on these elements, this review makes
current and future recommendations for effective gamification, such as the use
of virtual reality and adaptation of game difficulty to user skill level.
