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.