How is motor and cognitive performance modified using a visual-haptic interface?

Updated: Aug 20, 2019
  • Author: Morris Steffin, MD; Chief Editor: Jonathan P Miller, MD  more...
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Answer

Answer

Central to the ability to modify motor performance in patients with neurologic disorders is the means to apply corrective or cueing forces to the body parts involved in the activity. In patients with cerebellar tremor, for example, as occurs in multiple sclerosis, a movement such as reaching toward and grasping an object becomes extremely difficult, as demonstrated in the image below (panels A-F are stages of the movement in time).

Patient with cerebellar tremor showing free trajec Patient with cerebellar tremor showing free trajectory of wrist and hand movement. Force corridor is represented by 3 regions of interest (ROIs) as corridor limits. Graphs indicate degree of encroachment on ROIs as an attempt is made to reach the target.

The entire epoch, which lasts approximately 3 seconds, is shown fully graphed in the image below.

Patient with cerebellar tremor showing free trajec Patient with cerebellar tremor showing free trajectory of wrist and hand movement. Force corridor is represented by 3 regions of interest (ROIs) as corridor limits. Note failure to reach the target successfully (ie, the glass is overturned).

As the patient attempts to reach for the target object (ie, the glass), his hand oscillates rather than following a smooth and accurate trajectory. Interestingly, the terminal regions (thumb and fingers) are relatively stable, allowing for reasonably accurate grasping, but the wrist oscillations result in overturning rather than grasping the target object.

The successful trajectory for the patient's hand can be mapped out in advance once the target is selected. As long as the patient's wrist and hand remain within limits established by the position of the target, he or she will be able to reach it with stability. The spatial domain of these limits may be termed the force corridor. A device can be envisioned that applies force to counter the patient's wrist movement should the wrist deviate outside the corridor.


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