An estimated 16 million people per year worldwide experience a stroke, of which about two-thirds survive .
Six months poststroke, 30 to 66 percent of them show motor deficit of the arm contralateral to the lesion . Activity-based rehabilitation can improve upper-limb motor function ; this is of great importance, because lack of arm-movement control directly affects activities of daily living and independence .
To improve motor performance, both motor (re)learning and compensatory strategies are required [5-6]. Motor (re)learning and recovery are mainly possible because of plasticity of the brain , and the changes caused by plasticity in the lesioned hemisphere coincide with motor function improvement after activity-based rehabilitation . In addition to neural plasticity changes in the lesioned side, motor recovery may occur because of a shift of balance in the motor cortical recruitment toward the undamaged hemisphere via the ipsilateral pathways [8-9].
Movement practice and repetition form the basis of plasticity-based motor recovery [10-14]. A number of factors are thought to enhance plasticity-based rehabilitation, such as task-oriented movement practice in a challenging, engaging, functional, and meaningful way, and the rehabilitation should address body function and structures, activity, and participation level [9-13,15]. Rehabilitation has shown that, even in chronic stroke, improved upper-limb outcomes can be achieved [16-17].
Recovery after stroke correlates with the frequency and intensity of exercise [11,13,18-19]; however, passive movement is insufficient to alter motor recovery . Active engagement and movement attempts are thought to be more important than passive movement, and the focus should be on movement coordination rather than muscle strengthening .
Moreover, strong evidence exists that bilateral training is effective in functional recovery of the upper limb [20-21]. Summers et al. suggest that bilateral synchronous movement therapy is more effective than similar unilateral training . Bilateral therapy is based on the idea that involvement of the unaffected upper limb facilitates learning the spatial and temporal parameters required for motor recovery of the affected limb . Bilateral training is thought to increase activation of the affected hemisphere, especially the secondary motor areas, by interhemispheric connections [21-22].
Technology-assisted upper-limb training after stroke can provide engaging and task-oriented training in a natural environment using patient-tailored feedback to support (re)learning of motor skills . Computer and video games can improve therapy compliance through engagement . Gaming consoles like the Nintendo Wii (Nintendo; Redmond, Washington) and the Sony Eyetoy (Sony Computer Entertainment, Inc; Tokyo, Japan) are currently used in upper-limb stroke rehabilitation, although limited clinical evidence exists for their effectiveness [23-24]. Console games are designed for nondisabled people; therefore, they are often too fast for people with motor disabilities to use  and frequently provide negative feedback when a game is lost.
Robotic therapy has been reported to improve several motor control aspects (e.g., muscle-activation pattern, selectivity, and speed) and may have long-term effects . Robot-assisted therapy appears to improve motor control more than conventional therapy and is suited for rehabilitation in both the acute and subacute phase . However, the advantages probably exist only because a higher intensity of practice can be reached [13,27], resulting in improvement at a body function and structures level and not necessarily improvement in activities of daily living [13,26]. A disadvantage of robotic therapy is the cost; thus, an important question regarding the future of robotic rehabilitation is whether similar objectives can be accomplished by a simpler and more cost-effective approach [28-29]. …