Training the Motor Cortex by Observing the Actions of Others During Immobilization

Abstract

Limb immobilization and nonuse are well-known causes of corticomotor depression. While physical training can drive the recovery from nonuse-dependent corticomotor effects, it remains unclear if it is possible to gain access to motor cortex in alternative ways, such as through motor imagery (MI) or action observation (AO). Transcranial magnetic stimulation was used to study the excitability of the hand left motor cortex in normal subjects immediately before and after 10 h of right arm immobilization. During immobilization, subjects were requested either to imagine to act with their constrained limb or to observe hand actions performed by other individuals. A third group of control subjects watched a nature documentary presented on a computer screen. Hand corticomotor maps and recruitment curves reliably showed that AO, but not MI, prevented the corticomotor depression induced by immobilization. Our results demonstrate the existence of a visuomotor mechanism in humans that links AO and execution which is able to effect cortical plasticity in a beneficial way. This facilitation was not related to the action simulation, because it was not induced by explicit MI.

Dissociating effect of upper limb non-use and overuse on space and body representations

“…Although previous studies demonstrated that immobilization affects motor performance (Bassolino et al, 2012) and cortical excitability (Avanzino et al, 2011;Bassolino et al, 2013;Huber et al, 2006), this works is, at the best of our knowledge, the first report demonstrating the plastic properties of PPS representation after non-use. Before immobilization, the farthest distance at which sounds speed up tactile RTs was between D1 and D2 (corresponding approximately to a sound position perceived between 85 and 7 cm from the arm), and after non-use, this distance shifted to a position between D2 and D3 (corresponding approximately to a location between 70 and 50 cm), suggesting that PPS boundary around the constrained arm contracted.…”

Activating the motor system through action observation: is this an efficient approach in adults and children?

“…Further, a recent work on transcranial magnetic stimulation by our group has demonstrated that the reduction of the excitability of the hand area typically recorded after immobilization can be fully compensated when individuals observed hand actions performed by others. This result suggests that action observation can prevent the cortical effects induced by inactivity in healthy adults …”

Can we simulate an action that we temporarily cannot perform?

“…If alterations are established, interventions using motor imagery or action observation might be tested with the aim of maintaining motor representations and compensating for the lack of sensorimotor input during the period of injury [5,52].…”