Neuroplasticity of imagined wrist actions after spinal cord injury: a pilot study

Motor imagery (MI - i.e., the mental representation of an action without physically executing it) stimulates brain motor networks and promotes motor learning after spinal cord injury (SCI). An interesting issue is whether the brain networks controlling MI are being reorganized with reference to spared motor functions. In this pilot study, we tested using magnetoencephalography (MEG) whether changes in cortical recruitment during MI were related to the motor changes elicited by rehabilitation. Over a 1-year period of inclusion, C6 SCI participants (n = 4) met stringent criteria for inclusion in a rehabilitation program focused on the tenodesis prehension (i.e., a compensatory prehension enabling seizing of objects in spite of hand and forearm muscles paralysis). After an extended baseline period of 5 weeks including repeated MEG and chronometric assessments of motor performance, MI training was embedded to the classical course of physiotherapy for five additional weeks. Posttest MEG and motor performance data were collected. A group of matched healthy control participants underwent a similar procedure. The MI intervention resulted in changes in the variability of the wrist extensions, i.e., a key movement of the tenodesis grasp (p < .05). Interestingly, the extent of cortical recruitment, quantified by the number of MEG activation sources recorded within Brodmann areas 1–8 during MI of the wrist extension, significantly predicted actual movement variability changes across sessions (p < .001). However, no such relationship was present for movement times. Repeated measurements afforded a reliable statistical power (range .70–.97). This pilot study does not provide straightforward evidence of MI efficacy, which would require a randomized controlled trial. Nonetheless, the data showed that the relationship between action and imagery of spared actions may be preserved after SCI.