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A Systematic Review on Serious Games in Attention Rehabilitation and Their Effects

Attention is a basic and main mental task and can play an important role in the functioning of other brain abilities such as intelligence, memory, learning, and perception, and its deficit occurs in 80% of patients with traumatic brain injury. The use of game-based tools for rehabilitation is rapidly expanding. Cognitive rehabilitation via video games is an emerging hot topic in cognitive science. Serious games serve a specific purpose in addition to entertainment. They can be more engaging than exercises since they replace reward and motivation systems with real-world motivations as a complement for rehabilitation activities. This study was aimed at identifying and categorizing serious computer games used for attention rehabilitation and evaluating their effects. Six electronic databases (Scopus, PubMed, ISI, Embase, IEEE, and Cochrane) were searched in August 2021. The search strategy consisted of three main concepts of “serious game”, “cognitive deficits”, and “cognitive rehabilitation”. The inclusion criteria were (1) journal articles, (2) English language, (3) being published in the last 10 years, (4) human participants, and (5) game-based intervention. In the 30 included studies, 22 unique games were utilized for attention rehabilitation. Lumosity (20%), Brain Age (Dr. Kawashima's Brain Training) (10%), and MoHRS (6.66%) were the most common games among the studies. There were (57%) casual, (23%) action, (10%) simulation, and (10%) multiple genres. Of the 47 tools used in the studies, 5 utilized cross-modal oddball attention tasks, 4 utilized game performance, 3 utilized the paced auditory serial additional test (PASAT), and the rest employed other tools. A total of 73 outcome measures were related to attention, 42 measures did not have significant results, 30 were significantly improved, 1 was significantly deteriorated, and 4 articles did not have any specific measures for attention evaluation. Thus, the results revealed the positive effect of serious games on attention. However, issues such as absence of scientific teams, the variety of the disorders that cause defects, the variety of criteria, differences in measurements, lack of long-term follow-up, insufficient RCT studies, and small sample sizes should be considered when designing, developing, and using game-based systems to prevent bias.


Introduction
Attention is defined as a set of complex psychological functions that include focusing or engaging with the goal, enduring, and being alert for a long time. It is a feature in the human brain that allows a limited amount of information to be actively processed. This information is taken from the vast amount of information available to the senses, stored memory, and other cognitive processes [1]. It is the basis of cognitive functions because any defect in its function can decrease cognitive efficiency [2], and its improvement can greatly contribute to the rehabilitation process of stroke patients [3]. Attention is a major mental task and can also play an important role in the functioning of other cerebral abilities such as intelligence, memory, and perception [4]. Attention deficit can be caused by various diseases and disorders such as multiple sclerosis, traumatic brain injuries, and stroke. In each of these neuropsychological situations, there are different physical and cognitive symptoms in patients [5]. The attention control system is one of the most complex control procedures in our nervous system. Different networks distributed in the brain are involved in different aspects of the attention control system. Interactions between and within these networks of attention are mediated by various inhibitory and excitatory neurotransmitters. These neurotransmitters play a vital role in the proper functioning of the attention control system, and their interaction is essential. Any defect in neurotransmitter interactions can lead to dysfunction of attention networks and consequently dysfunction of the attention control system [6].
Attention is defined as awareness of what is happening around us [7]. Its deficit is very common and usually occurs in 80% of patients with traumatic brain injury, slowing down the patient's reactions in daily life and increasing irritability [8]. The model of Sohlberg and Mateer [9] classifies attention into five different categories of focused, sustained, selective, alternating, and divided attention [9]. In terms of types of stimuli and due to the existence of five senses in the human body, it is divided into 5 categories: visual, auditory, tactile, olfactory, and gustatory [6]. Also, attention can be divided into two broad categories: intensive processes, such as alertness and vigilance, and selective attention processes, such as focused and divided attention. Aspects of intensity could be a prerequisite for more complex aspects, such as selective [10,11]. In fact, lack of attention is associated with problems with balance, daily life functions, and falls [12]. Due to the high impact of attention deficit on other cognitive and physical functions, many researchers have tried to provide effective treatment options for this deficit [13].
Researchers are now well aware that the brain is a more flexible organ than previously thought and is able to significantly repair damage by reorganizing itself, which is the basis of functional rehabilitation. This feature is called neuroplasticity of the brain [14]. It is shown that the brain can repair itself after injury through repetitive, intensive, and task-oriented exercises [15]. Cognitive rehabilitation, behaviour adjustment, psychological management, education, and individual and family counselling are the primary methods of treatment in the rehabilitation of attention deficits [16]. Many researchers have emphasized the importance of cognitive rehabilitation in reducing behavioural and cognitive consequences and promoting independence and quality of life [14,17,18]. Cognitive rehabilitation currently generally uses one of the two approaches to treating cognitive deficits. (a) The therapeutic or restitution approach seeks to directly retrain impaired cognitive function. The basic rationale for this approach is the notion that practicing carefully selected exercises improves damaged neural circuits and restores function in the damaged attention processes themselves. (b) The alternative or compensation approach helps people with attention deficits learn or relearn how to perform specific skills. The basic rationale for this approach is that new neuropsychological processes replace the damaged areas of the brain through practice and develop individual skills [19,20]. Most studies have pointed to the positive effect of cognitive rehabilitation on attention deficit due to various diseases in both approaches, especially in the compensation approach [21][22][23], but at the same time, some studies are ambiguous about this positive effect in the long time [23,24].
Still, the most important challenge for therapists is how to encourage patients to perform rehabilitation programs frequently [25,26]. Today, cognitive rehabilitation methods can be divided into two main categories: traditional methods and computer-based methods. Traditional methods use noncomputer neuropsychological techniques to improve attention and concentration deficits. The traditional rehabilitation is done face-to-face; that is, one or sometimes several therapists work with a patient [27]. These methods have many limitations such as lack of access in all places, high travel costs, lack of accurate monitoring, dearth of information about the patient's performance, and being dull due to their repetitive nature [28,29]. Computer-based methods use similar neuropsychological processes but utilize the computer for training as an adjunct to face-to-face rehabilitation that will solve the problems associated with traditional methods [29][30][31]. Several studies suggest that providing feedback, training strategies, and intervention control by the therapist, along with technology, can improve outcomes [31][32][33].
Over the past few decades, evidence has highlighted the positive impact of computer-based rehabilitation programs on a variety of deficiencies [31,[34][35][36][37][38]. Among these interventions, the use of game-based tools for rehabilitation is rapidly increasing [39]. Serious games are games that serve a specific purpose in addition to entertainment [40]. The use of serious games in physical rehabilitation has a long history, but this method in cognitive rehabilitation, although scientifically a hot topic, is still not practically and widely practiced [41,42]. Serious games can be more engaging than exercises because they replace reward and motivation systems with real-world motivations as a complement to rehabilitation activities. People can be immersed in the game world, and their ability and knowledge can be improved without any danger [43]. Other features of these games are increasing the quality and effectiveness of rehabilitation, providing different levels of play to people according to the severity of defects and overcoming the limited resources and facilities of conventional rehabilitation methods [44]. Coles et al. [45] used computer games to teach safety knowledge to children with cognitive impairments, and Prang et al. [46] utilized computer games to rehabilitate disabled patients. Traditional rehabilitation exercises require repetitive and dull activities that are not completed by patients. Moreover, most people today are familiar with digital environments, especially mobile phones. Therefore, health professionals are interested in using computer games for rehabilitation purposes, which will both enhance motivation and determine the outcome of rehabilitation [47,48].
In this qualitative literature review, we summarize findings about serious games in attention rehabilitation. The objectives of this review are as follows:

Materials and Methods
Herein, we present a systematic literature review of serious games for attention rehabilitation based on the PRISMA checklist 2020 [49]. This review identified and classified relevant studies on serious games and summarized the findings and gaps. To be flexible in the search, we used parallel and iterative processes for screening, classification, and review phases.
2.1. Eligibility Criteria. The eligibility criteria were as follows: (1) being a journal article, (2) being written in English, (3) being published in the last 10 years, (4) human participants, and (5) providing any game-based intervention. Studies would be excluded from the study if they were (1) unrelated and (2) duplicated; (3) had unavailable full texts or were abstract-only studies; (4) were of other types, e.g., reviews, (5) involved no video games or cognitive rehabilitation; and (6) were protocols and studies only about Exergames.

Information Sources and Search
Strategy. According to the AMSTAR guidelines, at least two databases have to be searched in a systematic review [50]. To obtain more accurate and exhaustive results, we increased the number of searched databases. Six electronic databases (Scopus, PubMed, ISI, Embase, IEEE, and Cochrane) were searched on 2 August 2021 for articles published from January 2011 to August 2021. In addition, to ensure the search of all related articles and reduce the possibility of bias, a manual search was performed using two methods: (1) checking the references of the related papers and (2) using the Google Scholar search engine. We adopted the PICO approach to prepare the search terms [51]. The research team jointly selected three different categories of keywords "serious game", "cognitive deficits", and "cognitive rehabilitation" to achieve the objectives of the study and the exhaustiveness and sensitivity of the search. Then, we used MeSH, Emtree, and other related papers to find all the keywords related to these categories. During the primary search, we found that some articles with topics and themes cognitive rehabilitation, executive function, memory, perception, problem solving, etc. also considered attention along with these topics; thus, to cover these articles as well, we used the term cognitive as the more general term instead of attention. To extract more information about games that were not fully described by the included article, Internet resources and other articles were searched. We also searched the websites of the games to obtain the latest release information.
2.4. Risk of Bias Assessment. Because we aimed to provide a classification of articles and games available for attention rehabilitation and evaluate their overall effects, at this phase, we did not intend to conduct a meta-analysis on the data; therefore, we did not perform a quality assessment of the included studies.

Synthesis Methods and Analysis.
According to the objectives, comparative tables and figures are presented to describe and categorize the results. With a qualitative analysis method, we combined and analysed the results and no meta-analysis was performed due to the heterogeneity of the outcome measures and differences in the populations. Prior to this step, data were checked and refined to provide better results. Excel 2016 was used to present and analyse the data.

Results
3.1. Selection of Studies. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) flow diagram of the study selection process is displayed in Figure 1. Initially, 3,937 studies were obtained from six scientific databases; after removing the duplicates, the remaining 1,672 articles were screened based on the titles and abstracts. The screening process resulted in the exclusion of 1,369 articles based on the inclusion and exclusion criteria. Then, 303 articles were downloaded in full text for further screening. Of these, 282 were excluded after reviewing their full text for various reasons, e.g., administering the intervention to nonpatients, games with physical activities, lack of gamification, noncognitive rehabilitation intervention, or being review articles. From these databases, 21 articles entered the final phase of inclusion, and 9 articles were manually searched. Finally, 30 articles were selected for data extraction. The results are visualized using the PRISMA flow diagram in Figure 1.  Table 1). The highest target group of the games was the elderly 10 (33%) and those with traumatic brain injury 6 (20%). Other target diseases include autism spectrum disorder, ADHD, at-risk children, developmental disabilities, HIV, dementia, dyslexia, neglect disorder, neurocognitive disorders, stroke, and multiple sclerosis (MS). Evidently, the target groups in the studies were very diverse. Moreover, 12 (40%) of the studies were RCTs, while the rest were of other types such as prepost (6, 20%), pilot RCT (4, 13%), quasi-experimental (3, 10%), case series (2, 6.66%), singlesubject (2, 6.66%), or uncontrolled clinical trial (1, 3.33%). Most studies were conducted in Italy (4, 13%) and Spain (4, 13%), and some studies were the result of the collaboration of several countries.
All included interventions belonged to different types of computer technologies involving gamification. On the other hand, there were various types of control groups. Most  Most studies had a sample size of more than 10 (25 out of 30). Studies with a small sample were often comprised a virtual reality (VR) or augmented reality (AR) intervention group (8,9,29). The largest sample size was 232 and 157, respectively (24,5), while the other sample sizes were below 60.
Video game genre refers to categories of games with similar gameplay characteristics, usually not defined by the story and the setting (unlike cinema) but by how the player interacts with the game [81]. Genres cover a wide range of games and are further branched into subgenres. For example, a simulation game is classified into subgenres such as sports and process games [81]. Of all the included articles, there were 17 (57%) casual, 7 (23%) action, 3 (10%) simulation, and 3 (10%) multiple genres. Among the casual genre studies, there were 1 (6%) item with board games, 11 (65%) puzzles, and 5 (29%) multiple subgenres. In the action genre, there were 3 (43%) items with first-person shooters, 3 (43%) platformers, and 1 (14%) role-playing game (RPG) subgenre. Of the simulation genre studies, there were 1 (33%) item with process and 2 (67%) sport. All multiple genres also had multiple subgenres (3, 10%). Figure 4 illustrates the genres and subgenres of games according to the platforms used in the articles.

Brief Description of the Games Involved.
In this section, we will briefly describe the features of the games included in the study. All the games along with some of their features are listed in Table 2.
FarmerKeeper is a brain-computer interface video game developed by Mercado et al. to support neurofeedback training for children with autism spectrum disorder [52]. Neurofeedback can regenerate and retrain brain activity to enhance cognitive function in healthy individuals and those with certain developmental neurological conditions [82,83]. The game takes place on a farm. The object is to keep children's attention above a certain threshold to control a runner who is looking for lost farm animals to bring them back to their pen.
Dr. Kawashima Brain Training for the Nintendo Switch is the fifth entry in the Brain Age puzzle video game series. It is based on research by neurologist Ryuta Kawashima whose avatar guides the player throughout the game. The Italian version of the game was used in the study by De Giglio et al. [53]. The minigames included in this game set include calculations, voice calculation, reading aloud, low to high, syllable count, head count, triangle math, and time lapse. In calculation, simple math questions appear on the screen very quickly and the player has to write the answer on the touch screen. In voice calculation, the answers must be said aloud. In reading aloud, a piece of a classic story should be read as soon as possible. In low to high, the position of num-bers that appear on the screen for a short time should be memorized, and the player should demonstrate numbers from lowest to highest. In syllable count, the number of syllables in each sentence is counted. In head count, the screen above shows a group of people. After a few seconds, they are enclosed by a house and soon start coming in and out of the house. The player must count the number of people currently in the house. In triangle math, equations consist of 3 numbers and 2 operations and the player must perform operations in two modes, e.g., 7 + 5 + 4 and ð7 + 5Þ + ð5 + 4 Þ. In time lapse, the time difference between the 2 analog hours must be calculated.
Labyrinth includes a little man moving in the maze to reach the goal. The game character is controlled with a joystick by the gamer. The level of difficulty changes according to the task. The game consists of two tasks: diamond task and snake task. Each task has eight difficulty levels on a continuum from lower (level 1) to higher levels (level 8). The purpose of the game character depends on the nature of the current task. In DT, the man must collect diamonds that are randomly distributed in the play area. In ST, he must avoid being caught by a snake and reach the shelter house which appears in a random place.
Lumosity includes 50 games, 10 of which are specifically related to attention (Assist Ants, Feel the Beat, Skyrise, Eagle Eye, Playing Koi, Trouble Brewing, Train of Thought, Lost in Migration, and Star Search). In the included studies that have used the Lumosity package, different minigames have been utilized. Here, we provide a brief description of the games related to attention only. Assist Ants is designed to challenge your divided attention. You need to ensure the safety of each ant by helping it avoid collisions. Feel the Beat practices a sense of timing and rhythm. You have to rely on audio cues and use your sense of rhythm to match the beats in each experiment. In Skyrise, the goal is to work on your field of vision. In this game, several squares with numbers inside them appear. You have to memorize all the numbers and select them in ascending numerical order. The main goal of Eagle Eye is to improve your peripheral vision. You need to focus on the white circle in the middle and memorize the symbol or number that appears there. The goal of Playing Koi is to feed all the fish in the pond only once. In Trouble Brewing, you have to prepare a certain number of coffee orders in 2 minutes. In Train of Thought, you must guide each train to the matching station by switching the route keys. In Lost in Migration, the herd stays at one point and your task is to determine the path that the middle bird is facing. In Star Search, players must quickly find a unique object among a set of items that have the same shape, color, movement, and texture.
Captain's Log marketed by Brain Train Corporation is a comprehensive suite of computer cognitive learning games consisting of more than 2,000 computer-based exercises targeting 20 cognitive skills. Training modules are presented as games in which students' performance is recorded and points are earned based on performance accuracy.
Rayman Raving Rabbids includes 75 minigames and has two modes of play: story mode and score mode. In the story mode, the game follows 15 days of Rayman's imprisonment 18 Behavioural Neurology by the Rabbids. Every day, Rayman must do at least three trials. In the score mode, players can repeat previous trials to improve their scores. Kinect Sports Ultimate Collection simulates 13 sports: basketball, soccer, American football, bowling, beach volleyball, table tennis, boxing, golf, tennis, skiing, darts, baseball, and track and field. To improve performance, songs and comments are used to help control and play the games.
AR-Therapist is a simulated augmented reality (AR) environment using a simple game. The game simply simulates two balls in 3D; one is the target ball and the other is not. The player must hit the ball at a specified time which, if correct, will add to the value of the correct shots. Otherwise, the value is added to the errors.
CogARC uses the AR interaction technique and manipulation of tangible physical objects (cubes) for cognitive screening and training. This game includes 6 minigames. Game mechanics include challenges, competition, feedback, and rewards. The gameplay structure offers two modes: free and linear. The player can play the minigames freely (free mode), in any order and at the desired levels, or play all the minigames in a predetermined order (linear mode). The minigames include Shape Match in which similar shapes should be matched, Color Match where you have to match the meaning of one word with another word's color, Sum Tower that uses numbers to create the desired sum, Building Blocks where you should find the answer to simple arithmetic calculations, Pattern Memory where you have to memorize and recreate a 3 × 3 matrix pattern of colored tiles, and Word Game where words related to a specific topic must be found.

Medal of Honor: Rising Sun (MoHRS) is a first-person
shooter video game, the fifth in a series of Medal of Honor released by EA Game. Rising Sun is set in World War II during the Pacific War and has single and multiplayer capabilities.
The VR-based serious game application comprises several daily life activities such as buying several items, finding the way to the minimarket, finding a virtual character dressed in yellow, and recognizing outdoor advertisements, devised to train cognitive functions.
The Brain Powered Games (BPG) package includes Butterfly, iSpy, Stampede, Whacky Animal, and Gone Fishing. Butterfly is a simple game in which a butterfly flies on the screen and the player must use a mouse or other input devices to move the butterfly when it stops moving at a random location. iSpy is a memory game that works based on a common learning and memory pattern. The player is asked to watch a scene. After a brief display, the image is removed with a short delay and then represented, and the player is asked to click on the new item(s) that were absent in the previous image. In Stampede, the player sees a special animal to be memorized. Then, a group of animals appear spinning on a computer screen, and the player has to click only on the animal that was originally presented. In the Whacky Animal training program, the player is shown animals that must be memorized; as the animals appear randomly on the screen, they must be clicked or touched before disappearing behind the screen. In Gone Fishing, the player has to fish by following the bobber and clicking on it.
In Duckneglect, the player is told to tap one or more objects belonging to a particular class (targets) that appear      23 Behavioural Neurology on the screen in a virtual scenario and to avoid distractions with the hand contralateral to the neglected space. The goal of this game is to guide players through visual search tasks.

Behavioural Neurology
MeMo is divided into two parts, and the first part involves memory. The second part involves flexibility and mental attention, which includes the following three activities: Arrows for processing speed, inhibitory control, and mental flexibility training; Tricky Cards for working memory training; and Jumping Squares for reaction anticipation and inhibitory control training.
BrainHQ includes 29 exercises that cover six areas of cognition, including memory, attention, speed, people skills, navigation, and intelligence.
Video game tasks involves two types of tasks to train attention: the flow task and the control task. These tasks have the same content, except that the flow task is designed by increasing the difficulty of the task according to the patients' skills and providing clear goals and quick feedback on the score. The task includes Square, Click Number, and Tower. In the Square task, patients must control a central blue square with the mouse and prevent red squares from entering the right, left, top, or bottom of the screen. If the squares coming towards the blue square are black, patients get points for hitting them. In the Click Number task, patients must click and delete disks in numerical order. In the Tower task, blocks of three colors are randomly stacked. Patients should click and delete the right, left, or center of the block based on its color as soon as possible. The removal time of all the blocks is calculated.
Caribbean Quest (CQ) is composed of five cognitive games: Scuba, Submarine, Wave, Pirate Delicatessen, and Squidditch. Scuba and Pirate Delicatessen are working memory games, Submarine and Wave are sustained attention games, and Squidditch is a selective attention game. Submarine and Wave are similar in cognitive tasks but different in terms of gameplay. Submarine is a static environment in which the player's only control is the selection of fish from the middle porthole, while the Wave allows the user to navigate an avatar in an ocean.
Brainastic includes 17 minigames, four of which are specific for attention. In Conveyor Belt, to learn versatility, you have to change the conveyor sorter and collect items with a specific color. In Spot the Difference, you need to find a unique insect to teach attention and the ability to filter information. In Film Collector, the film should be selected with a specific color or pattern to teach the immediate reaction to move objects. In Honey Haunters, to teach attention and the ability to filter information, you need to determine the correct number continuously over a short period.
RehAtt™ uses a 3D VR game environment to combine visual scanning training and multisensory stimulation. The hardware creates a virtual 3D world. The feeling of real touch and guidance is provided by a robotic pen and through vibrotactile feedback.
Video game therapy (Kinect Adventures and Kinect Sports) encompasses a wide range of physical activities. Kinect Adventures using full-body movement allows the player to participate in a variety of minigames. Kinect Sports is a collection of six sport simulations and eight small games designed to demonstrate the capabilities of Kinect motion. The six sports include bowling, boxing, athletics, table tennis, beach volleyball, and union football.
In Space Fortress, the player uses the joystick to steer a spaceship in an environment without friction and shoot the rocket into the space castle to destroy it; meanwhile, mines keep appearing on the screen.

Discussion
This study identified and categorized serious computer games used for attention rehabilitation and assessed the 24 Behavioural Neurology   27 Behavioural Neurology effects of these games. Game categories were presented based on game genres and different platforms. To the best of our knowledge, this was the first review on this subject. Bogdanova et al. [5] conducted a systematic review somewhat closely related to this study, but they examined computerized rehabilitation programs, not computer games. On the other hand, they considered only attention deficits after acquired brain injury. Also, the study by Norman et al. was somewhat similar and examined the effectiveness of cognitive rehabilitation programs after acquired brain injury [5,19]. Examples of the differences between serious games and traditional computer rehabilitation methods are the following: the ability to prevent boredom and monotony, increase motivation, and provide timely feedback and the ability to perform multitasking exercises, attractive visual interfaces, providing consistent content, and difficulty level according to the performance of players [85].
Out of the 73 outcome measures, 30 showed significant improvement and only one showed significant deterioration [55]. Furthermore, 19 of the 26 studies that performed attention evaluation had at least one significant improvement in their measures [42, 52-54, 56, 58, 61-66, 72, 73, 75, 76, 78, 80, 84]. Therefore, most studies support the effects of serious game-based computer interventions for attention rehabilitation. Although these results are promising, several methodological issues need to be addressed in future studies to determine the effects of interventions more accurately. For example, most studies did not have an appropriate sample size to ensure the significance and validity of the results, so that 20 out of 30 studies had less than 20 participants in the intervention group [52-54, 57-63, 65, 66, 69, 71-73, 75-79]. Also, 5 studies were performed with 1 to 5 participants [58,59,65,71,79]. In addition, the type and severity of the disease causing the attention deficit may have affected the outcome. Participants' age can also affect the rehabilitation process. Moreover, the control groups are different across studies; 11 studies provided routine care to the control group [53-55, 61-63, 66, 68, 70, 72, 77], whereas other studies included video, cartoon, and other active control groups. One-third of the studies did not have a control group at all, and out of 12 RCT studies, six studies include an active control group for comparison [57,60,73,74,78,84]. Evidently, considering routine care as a control group will increase the risk of bias; that is, the positive effect of the intervention may not be due to increased physical, group, and social activity [86]. Therefore, it is recommended that future studies include active control groups.
The lack of long-term follow-up was another problem. As observed in the study by Ballesteros et al. [54], the results demonstrated a significant improvement immediately after the intervention but a nonsignificant result on the three-month follow-up. This could also be true in the case of other studies; therefore, follow-up should be performed at longer intervals to evaluate the validity and persistence of the result.
The reviewed studies used different tools to measure attention and its subdomains. Some tools can be applied to all cognitive domains, while some are specific to the domain of attention or its subdomains. There is no standard for measuring attention, and this necessitates a comprehensive and appropriate standard for this purpose. Another important point in game design is the role of scientific teams in game design. Other studies emphasize the participation of therapists and scientific teams in the design process [5,36]. The benefits of being a therapist along with the use of these tools include higher patient motivation, better feedback for the physician, and better management and control of the device according to the patient's condition [31]. Most of the reviewed studies did not mention the exact process or the team involved in game development. The development of standard games with the participation of various scientific groups and stakeholders seems to be necessary for attention and its subcategories, and standard methods must be developed to use and evaluate the attention rehabilitation process. Unfortunately, the increasing growth of programmers and commercial companies producing games and medical equipment, without the use of specialized scientific groups, poses many dangers and harms to the health of people in the community. It can be seen that there are many commercial tools that are unjustifiably advertised in the market to improve various mental skills. There is a need to take action to solve this problem [31]. For example, in all tools or games in the field of public health, basic criteria can be defined, both based on the interface and usability and based on their content. Extensive clinical evaluation may be mandatory for all instruments to obtain a license to use. Also, systematic review studies can be helpful for this purpose.
Due to the insufficient RCT studies and the existence of various measures, it was not possible to perform a metaanalysis on the data. Moreover, the control groups greatly differed. For many games, no clinical trial was performed. There were also many articles on general cognitive rehabilitation in which attention rehabilitation was a subscale. Thus, the search was very comprehensive and we tried to overcome this limitation by conducting a more comprehensive search and excluding irrelevant articles.
As mentioned in the introduction, attention deficit disorder is usually associated with other cognitive impairments, and each of these deficits may have a positive or negative effect on the other. Perhaps it would have been better if this study had evaluated all these cognitive deficits together, but due to their great complexity and diversity, this was not possible in the study. Therefore, because attention deficit is fundamental and rehabilitation and improvement can help promote other cognitive deficits and reduce disability, we focused only on the area of attention deficit [5]. The fundamentality of attention skills means that, for example, attention skills support patients' visual and spatial perceptual ability to help predict next action. The ability of working memory is also required to temporarily store information to perform actions. On the other hand, maintaining patients' 28 Behavioural Neurology attention is a prerequisite for using their working memory ability [87].

Conclusions
In this systematic review, we reported game-based computer technologies for attention rehabilitation and assessed the effects of these games. In 19 out of 26 articles measuring the criterion of attention, at least one significant improvement was reported; therefore, it can be concluded that games created for attention rehabilitation are effective and patients and therapists can use the significant benefits of these games to rehabilitate attention deficits. However, to prevent bias, factors such as the variety of criteria and differences in their measurement, small sample size, lack of accurate evaluations of clinical trials on games, absence of scientific teams, lack of long-term follow-up, the existence of different control groups, and not including active groups for comparison should be considered when designing, developing, and using game-based systems. On the other, most of the games found in our study are presented on PC and virtual reality platforms, and for the benefits of portability and continuity of use, we suggest that more games be made for portable platforms such as mobile and tablet.