Effects of an integrative groupbased cognitive rehabilitation on cognition and brain connectivity in multiple sclerosis

People with multiple sclerosis (MS) may present deficits across a broad range of cognitive domains. Processing speed decline is one of the most common cognitive deficits in the disorder, and it can adversely affect the functioning of other cognitive processes. However, it is still unclear whether the distinct MS cognitive deficits occur as a result of processing speed decline or constitute independent deficits regardless of processing speed decline. On the other side, cognitive rehabilitation might be a promising therapeutic approach for addressing cognitive deficits in persons with MS. Nevertheless, further methodologically rigorous randomized clinical trials (RCTs) are required to attain a greater level of evidence for its efficacy in the disorder. Moreover, the neurobiological mechanisms underlying cognitive improvements following cognitive interventions are not yet entirely understood. The present research consists of three studies. The objective of the first study was to investigate the role of processing speed decline in other MS cognitive deficits. The second study aimed to assess the efficacy of an integrative group-based cognitive rehabilitation programme on improving cognitive functioning and daily functionality in persons with MS. The third study was targeted at examining brain functional and structural connectivity changes in response to the cognitive rehabilitation in MS, as well as the relationship between brain connectivity changes and cognitive improvements following the intervention. The results of the first study showed the presence of significant deficits in diverse cognitive domains (attention, processing speed, episodic memory, verbal fluency, and executive functioning) in people with MS; however these deficits became non-significant once the effect of processing speed was controlled. The results of the second study revealed significant cognitive improvements involving several domains (processing speed, working memory, episodic memory and executive functioning) in those persons with MS attending the cognitive rehabilitation. Finally, the third study showed that persons with MS also experienced significant brain functional connectivity decreases within the default mode network (DMN) and the hippocampal memory network (HMN) in response to the cognitive rehabilitation. Additionally, these functional connectivity decreases were significantly associated with some of the cognitive improvements detected following the intervention. In conclusion, present findings support that processing speed decline may to a large extent lie beneath other cognitive deficits in MS, underscoring the need for identifying the precise source of these deficits to better-inform intervention decisions. Furthermore, the findings of this research provide evidence for the efficacy of integrative group-based cognitive rehabilitations in MS, suggesting that this therapeutic approach can not only improve cognitive functioning but also induce adaptive brain functional connectivity changes in persons with the disorder.