Motion of the drawing hand induces a progressive increase in muscle activity of the non-dominant hand in Ramachandran?s mirror-box therapy

Abstract

Objective: To observe the real-time muscle activity of bilateral hands while subjects draw circles under 2 conditions: with and without using Ramachandran?s mirror-box. Subjects: A total of 24 healthy volunteers. Methods: Subjects drew 4 circles sequentially using their dominant hand with the other hand at rest, both with and without looking at a mirror image. Circles were marked by 8 dots on the paper, which subjects connected up to draw the shape. The activity of the bilateral first dorsal interosseus muscles was recorded using surface electromyography. Results: Muscle activity of the dominant hand remained constant during each task. In contrast, muscle activity of the non-dominant hand increased under the condition of watching the image in the mirror, but was low under the non-watching condition. Furthermore, muscle activity of the non-dominant hand increased over the duration of the task. However, wide variation between subjects was observed under the mirror-image condition. Conclusion: Increased muscle action potential of the non-dominant hand may be induced by the circle drawing task of the dominant hand during Ramachandran?s mirror-box therapy, which supports previous observations of increased brain activity caused by watching a mirror image.