Introduction: 

Short-term arm immobilization has been shown to induce a reduction of cortical activity of motor areas (M1) in healthy subjects (Huber et al., 2006). In the present study, we investigated whether ten hours of arm immobilization are able to induce modification of cortical excitability of M1 in both the hemispheres and to modulate transcallosal interactions.

Methods: 

To this issue, five right handed subjects (2 males and 3 females, mean age=24.4±2.5 years) wore a soft bandage able to prevent any movement on their dominant arm, from 8 a.m. to 6 p.m. Motor evoked potential (MEP) recruitment curve from right and left first dorsal interosseus and interhemispheric inhibition (IHI) both from left to right and right to left hemispheres were studied one day before and immediately after hand immobilization.

Results:

After immobilization MEP amplitudes decreased in the controlateral hemisphere, while they did not change in the ipsilateral one. Further, we observed a decrease of IHI from the controlateral to the ipsilateral hemisphere and a slight increase of IHI from the ipsilateral to the controlateral hemisphere.

Conclusions: 

Preliminary results show that ten hours of hand nonuse are able to reduce cortical excitability in the controlateral M1 and to modify the inhibitory interactions between hemispheres. These effects could be due to a decrease of both sensory afferent information and motor commands during the period of immobilization. Moreover, changes in interhemispheric inhibition could describe a "balance effect" between the two M1.