## 4 Discussion
showed a mean improvement of 1.5 points from 5.8 to 7.3 in the MMSE after 25 sessions (e.g., a total of over 16 h) of _CogMed_[31], which is comparable to the results reported herein: an average increase of 1.79 points in the DBS from 4.14 to 5.93 after 12 h of _Neuro-World_ play. It is noteworthy that _CogMed_ includes a game that specifically targets the DBS by displaying a sequence of numbers and instructing users to remember and reproduce the sequence in reverse order [31]. On the other hand, _Neuro-World_ includes games that ask users to remember and reproduce a sequence of animals, leaving a farm to train working memory, which does not replicate the DBS. There exist studies that reported statistically significant improvements in the DFS after conventional or game-based interventions [56; 60]. However, in our study, stroke survivors showed only non-statistically significant improvement in the DFS. This is likely because the participants in our study scored 7.36 on average at baseline, a relatively high score for the DFS [61], which yields limited room for improvement (i.e., ceiling effect). We envision a clinical scenario in which stroke survivors will first be introduced to _Neuro-World_ while they receive treatments in inpatient facilities. Then, stroke survivors could be prescribed to use _Neuro-World_ in outpatient facilities, in addition to the routine motor and cognitive rehabilitation programs, to enable frequent, low-cost, high-dosage cognitive rehabilitation in naturalistic settings. Stroke survivors' compliance level to _Neuro-World_ (e.g., frequency and duration of gameplays) can be summarized and made available to clinicians, such that clinicians can remotely follow up (e.g., a phone call or SMS) to improve patients' adherence to the intervention regimen. Although this remote management of stroke survivors may impose additional burden for clinicians, we believe mobile rehabilitation systems, in turn, will decrease the overall healthcare cost for chronic stroke survivors in the long-term [62]. We may also consider leveraging patient-centered mobile-health solutions (e.g., smartwatch or smartphone-based reminder systems) that use data-driven, personalized health information as part of reminders to promote positive health-related behaviors (e.g., adhering to at-home training) [63; 64]. For example, our prior study has shown that quantitative measurements of stroke survivors' game performance in _Neuro-World_ (e.g., average duration to complete a stage, the most difficult stages reached for each game, etc.) can be analyzed via machine learning algorithms to accurately estimate their cognitive level in terms of MMSE [40]. In other words, _Neuro-World_ could not only be used as a training tool but also as an assessment tool for cognitive level, such that patients can self-monitor the recovery process. Furthermore, clinicians could also use the information to closely monitor patients' longitudinal recovery trajectories and devise individually tailored therapy programs to maximize the chances of independent living, which is the ultimate goal of rehabilitation. The current study has several limitations. First, the study had a relatively small sample size. However, the preliminary results reported herein warrant a larger scale study, which would examine the effect of _Neuro-World_ with respect to the level of patients' education, different domains of cognitive function, stroke subtypes (e.g., size and location), or other medical factors. Second, the passive control group showed unexpected decreases in all outcome measures, where the decrease in the total MMSE score was statistically and clinically significant. At the completion of the data analysis, we subsequently followed up with the assessor to understand the potential factors that could have resulted in this unexpected decrease.