Cognitive and Motor Neurobehavioral Relationships in People with Multiple Sclerosis and Healthy Individuals

Even though cognition and motor behavior have been traditionally conceived as independent processes, a growing body of literature supports that motor and cognitive processes are highly interrelated (Hommel et al., 2016; Mirelman et al., 2018). The relative contribution of cognition -or executive control- to motor behavior has been evidenced by means of a behavioral approach (e.g. dual task) and/or a neurophysiological approach (Clark, 2015). In this context, a deeper understanding of the cognitive-motor interference that arises from the dual task performance of a motor and cognitive task is needed, as well as the characterization of cognitive demand in neural oscillatory activity in motor-related cortical regions of the brain. The general aim of this thesis is to examine the interplay between cognitive and motor processes by means of its effect on behavior and neural correlates in people with Multiple Sclerosis and healthy individuals. It will be achieved through the study of the cognitive-motor interference during dual-task performance in people with Multiple Sclerosis and healthy individuals, as well as through the study of oscillatory brain activity potentially associated with the cognitive demand during motor control in a healthy sample. The focus is not only theoretical but also applied since the cognitivemotor interference is evaluated for its applicability to the cognitive functional assessment of people with Multiple Sclerosis

The effect of prioritization over cognitive-motor interference in people with relapsing-remitting multiple sclerosis and healthy controls.

The cognitive-motor interference (CMI) produced by simultaneous performance of a cognitive and a motor task has been proposed as a marker of real-life impairment of people with Multiple Sclerosis (pwMS), yet there is no consensus on the dual task (DT) procedure. This study aimed to compare DT performance of pwMS and healthy controls (HC) under different instructions and to examine its association with neuropsychological and clinical variables. PwMS (N = 23; relapsing-remitting course) and HC (N = 24) completed the cognitive (Verbal Fluency) and motor (walking) tasks under three conditions: independently or as single task (ST), both tasks simultaneously at best capacity or double prioritization (DT-DP), and only the cognitive task at best capacity while walking at preferred speed or cognitive prioritization (DT-CP). Compared to HC, pwMS walked significantly slower and produced less correct words under all conditions. The distance walked by pwMS and HC significantly differed between conditions (DT-CP< DT-DP< ST). PwMS produced more words during ST respective to DT-DP and DT-CP, with no difference between both DT conditions. HC showed no differences in cognitive performance between conditions. Motor and cognitive dual-task costs (DTC) were similar between groups. Only in pwMS, the cognitive DTC of DT-DP was different from zero. CMI measures correlated with neuropsychological, symptomatic, physiological (cognitive event-related potentials) and clinical variables. These results suggest that cognitive performance while walking is impaired in pwMS, but not in HC. CMI over cognitive performance might be a potential early marker of cognitive decline in pwMS, which may be enhanced by the instruction to prioritize both tasks in DT