The inclusion and exclusion criteria assessments and the neurological examination will be performed by a blinded neurologist specialized in MS. The cognition, fatigue, depression, and quality of life assessment will be performed by a blinded neuropsychologist. The remaining assessments, including walking, balance, and motor imagery abilities will be assessed by a blinded physiotherapist. All the assessments will be performed before and after the training in the 6-week motor imagery training group. The participants in the wait-list control group will underwent the assessment with a 6-week interval. The healthy participants will be assessed only one.