Impaired Sequential but Preserved Motor Memory Consolidation in Multiple Sclerosis Disease.

Studies investigating motor learning in patients with multiple sclerosis (MS) disease highlighted that MS patients exhibit similar learning performance than healthy controls, but that learning can be hampered by the progression of MS eventually leading to impaired efficiency of subcortical-cortical networks. We aimed at investigating whether the long-term, overnight consolidation of sequential motor memories is preserved in MS disease. Thirty-one patients with MS and two healthy control groups (27 young and 14 middle age) were tested over two consecutive days using a serial reaction time task. Performance was tested (a) 20 min after the end of learning at Day 1 to monitor transient offline, short-term increase in motor and sequential performance and (b) after 24 h on Day 2 to quantify overnight delayed changes in performance reflecting memory consolidation. Besides a slower overall RT in patients with MS, motor performance similarly evolved in all groups. Sequence learning as assessed by interference effects was similar in patients with MS and both control groups on Day 1 (Learning and 20-min test). In contrast, while interference effects keep increasing on Day 2 after 24 h (Relearning) in healthy control groups, it reverted to levels reached at the end of learning for patients with MS. Long-term consolidation of sequential knowledge is impaired in patients with MS. At the motor level, learning and overnight consolidation abilities are preserved in MS disease.

Cognitive Fatigue, Sleep and Cortical Activity in Multiple Sclerosis Disease. A Behavioral, Polysomnographic and Functional Near-Infrared Spectroscopy Investigation.

Patients with multiple sclerosis (MS) disease frequently experience fatigue as their most debilitating symptom. Fatigue in MS partially refers to a cognitive component, cognitive fatigue (CF), characterized by a faster and stronger than usual development of the subjective feeling of exhaustion that follows sustained cognitive demands. The feeling of CF might result from supplementary task-related brain activity following MS-related demyelination and neurodegeneration. Besides, CF in MS disease might also stem from disrupted sleep. The present study investigated the association between the triggering of CF, task-related brain activity and sleep features. In a counterbalance mixed design, 10 patients with MS and 11 healthy controls were exposed twice for 16 min to a CF-inducing dual working memory updating task (TloadDback) under low or high cognitive demands conditions, counterbalanced. Considering known inter-individual differences and potential cognitive deficits in MS, the maximal cognitive load of the task was individually adapted to each participant's own upper limits. During the experimental sessions, cortical brain activity was measured using near-infrared spectroscopy (NIRS) during the CF-induction task, and in a resting state immediately before and after. Ambulatory polysomnography recordings were obtained on the nights preceding experimental sessions. When cognitive load was individually adapted to their processing capabilities, patients with MS exhibited similar than healthy controls levels of subjectively perceived CF, evolution of performance during the task, and brain activity patterns. Linear mixed models indicate a negative association between oxygenation level changes in the dorsolateral prefrontal cortex (DLPFC) and the triggering of subjective CF in patients with MS only. Longer total sleep time was also associated with higher CF in MS patients. These results suggest that controlling for cognitive load between individuals with and without MS results in a similar task-related development of subjective CF. Besides comparable performance and cortical brain activity between groups, mixed model analyses suggest a possible association between CF, DLPFC activity and sleep duration in MS disease.

Relative contribution of cognitive and physical disability components to quality of life in MS.

BACKGROUND: Information on the relative influence of cognitive and physical impairment on the quality of life in multiple sclerosis is currently limited and no scientific consensus has been reached yet. OBJECTIVE: For this reason, we wanted to examine the relative contribution of cognitive and physical impairment measures comprised in the MSFC test on quality of life in MS. METHODS: In the National MS Center Melsbroek, patients regularly undergo MSFC and EQ5D measurements. We investigated the correlations between the EQ5D, EQVAS and the MSFC and EDSS scores by the use of ANOVA and multilinear models. RESULTS: We found a significant correlation between the EQVAS score and cognition in a univariate model. When including EDSS score and MSFC outcomes into the model, cognition was, however, excluded based on the Akaike Information Criterion. Cognition was, on the other hand, a significant predictor for the "Usual Activities" question of the EQ5D. CONCLUSIONS: Although cognitive performance as measured on the PASAT-3s does not correlate with a patient's perceived quality of life in a multivariate model, it remains an important predictor for the patient's usual activities.