The aim of the study is to optimise the hand dexterity exercising program in virtual reality (VR) for patients with multiple sclerosis and Parkinson's disease. Little research has been published on this topic, but the preliminary results are promising. Different levels of difficulty of a VR game will be tested. The patients will be assessed using neuropsychological tests of executive functions, visuospatial abilities, mental speed, flexibility and motor speed. Functional ability, coordination and cognitive abilities will also be assessed.

Each patient meeting the inclusion criteria will be randomised to one of the four groups (i.e., 10cubes game difficulty level). The patients will perform five exergaming sessions, each session lasting for 1 hour, on five consecutive working days within the period of two weeks. The 10cubes task requires that all 10 cubes are moved within 2 minutes. Each patient will perform the task 5 times in succession with 1-2 minute breaks. The patients will be assessed using the Box & Blocks Test, Frontal Assessment Battery (FAB), Delis-Kaplan Executive Function System (D-KEFS) and Judgment of Line Orientation (JLO) before the first session and after the last session. In addition, the patients will fill in the Intrinsic Motivation Inventory (IMI) after each session. Based on statistical sample size calculations, the study plan is to include 80 patients with Parkinson's disease and 12 patients with multiple sclerosis randomising them separately, so that the groups will be balanced in terms of size and diagnosis.

Inclusion Criteria:

• diagnose of Parkinson's disease or multiple sclerosis;
• Mini Mental State Examination score above 24;
• preserved upper limb function;
• for Parkinson's disease patients Hoehn and Yahr scale score between 2 and 3.

Exclusion Criteria:

• any communicable disease;
• severe vision impairment.