The effect of cyclic illusory movement on corticospinal excitability of muscles in the contralateral limb

 

Yumi Umesawa, Kento Nakagawa,
Qi Weihuang, Satoshi Miura,
Yo Kobayashi, Masakatsu Fujie,
Kazuyuki Kanosue, ○Hiroshi Fujimoto

 Recently the number of bedridden older people caused by falling is increasing. No physical activity decreases not only motor function in each body part, but also function of coordination between body parts. In order to propose new rehabilitation tools, we focused on kinesthetic illusion that is passively elicited by vibrating  muscle tendon without actual movement (Goodwin et al. 1972), and the experimental model of neural modulation of resting one hand depending on the cyclic movement of the contralateral hand (Carson et al. 2004). We tested whether just kinesthetic illusion as well as voluntary movement modulates corticospinal excitability depending on the phase of illusory movement.

The experimental tasks were 1) voluntary movement, 2) kinesthetic illusion induced by tendon vibration (80Hz), 3) passive movement. Each task was periodical movement of left hand (0.75Hz). Transcranial magnetic stimulations of the left motor cortex were delivered during the phase of extension or flexion of left wrist, and then motor evoked potentials (MEPs) were recorded from of resting right forearm muscles. The results showed that vibration stimuli for the left wrist with kinesthetic illusion modulated the MEPs amplitude in the resting right wrist muscles depending on illusory movement phase just as observed during voluntary or passive movement. Additionally, the modulation did not occur in the subjects who had no kinesthetic sensation in illusion task.

In conclusion, kinesthetic illusion of single limb may produce the phase-dependent modulation of corticospinal excitability of contralateral limb, which can be efficient rehabilitation tools of inter limb coordination function.