Functional connectivity as a neural correlate of cognitive rehabilitation programs' efficacy: a systematic review

Researchers who have been assessing the efficacy of cognitive rehabilitation (CR) programs are expressing a growing concern with the validity of the assessment protocols and have tried to improve them by including multidomain measures in addition to cognitive and behavioral ones. Within this scope, changes in brain functioning associated with CR are being reported through the analysis of neural correlates. Nonetheless, the influence of CR on functional connectivity (FC) and its relationship with the behavioral outcomes conventionally used are still unclear. A systematic review of the literature was performed, up to January 2021, through a search on EBSCOhost, PubMed, and Web of Science, which targeted empirical studies assessing the efficacy of CR programs in adults, with FC as an outcome. This review included 51 studies, whose methodological quality was assessed through Cicerone's classification. We present the characteristics of the studies, the cognitive rehabilitation programs, as well as the techniques, protocols and methods used to measure FC. All of the CR programs used in the studies were associated with significant improvements in FC, and the majority of these programs were also related to significant improvements in behavioral outcomes. In addition, 32 studies that analyzed the relationship between behavioral and neural outcomes had reported that changes in FC were significantly associated with improvements in behavioral outcomes, namely in cognitive functioning, quality of life, and affective domains. Despite the high methodological heterogeneity of the studies, FC seems to be a proper indicator of the efficacy of CR programs, unveiling the importance of its use combined with behavioral outcomes.