Inclusion Criteria:  Common criteria:  Berg Balance Scale < 50/56; Ability to maintain the standing position with o without one support for 1 minute; Functional Independence measure < 100/126; Barthel Index < 80/100.  Stroke:  Single ischemic stroke; Lesion occured after 2 and within 18 months; National Institute of Health Stroke Scale ≤ 14.  Parkinson:  1.5 < Hoehn & Yahr < 3; Subitem "freezing when walking"of the UPDRS ≤ 2.  Multiple Sclerosis:  Relapsing remitting or secondary progressive Multiple Sclerosis; Expanded Disability Status Scale ≤ 6.5.  Exclusion Criteria:  Untreated epilepsy; Major depressive disorder; Fractures; Dementia; Ideomotor Apraxia; Neglect; Severe impairment of verbal comprehension; Severe acoustic and visual disorders.