Neural correlates of visuomotor transformations using the Rehabilitation Gaming System (RGS): actual and imagined target catching

Aims: The Rehabilitation Gaming System is an interactive computer simulation tool used to improve rehabilitation of motor deficits in stroke or other neurological patients. Based on a virtual reality RGS mimics the movements of the user by two virtual arms of an avatar integrated in a virtual environment. We assumed that combined observation, imagination and active execution of movements induce neural reorganization and fascilitate functional recovery.

Method: In this event-related function magnetic resonance imaging (fMRI) study investigating the brain system engaged in these processes, we used statistical parametric mapping with random effects analysis in 18 healthy, right-handed subjects (24±3 years). In 1st and 3rd person perspective views, subjects were required to passively observe, actively catch or imagine catching a coloured ball approaching from the horizon. The intention to catch the ball was indicated by a left or right button-press.

Results: During active catching, subjects anticipated the catch by on average 248 ms succeeding in 94±9 percent of the trials. This was associated with a decrease of activity in right inferior frontal gyrus and inferior parietal lobule. In the imagination task, the ball disappeared after 2.5 seconds requiring the subjects to imagine its flight path and catching. The button press was timed with a short delay of 55 ms succeeding in 75±29 percent of the trials. This led to activations (p<0.005, uncorrected) in right inferior and medial frontal cortex, bilateral inferior parietal lobule and left cerebellum. Compared to the 1st person perspective, the 3rd person perspective involved the right anterior medial frontal cortex in both tasks.

Conclusion: RGS induced changes in higher order brain circuits in relation to visuomotor control. This can provide a neural basis for this crossmodal neurorehabilitation approach.