Neural substrate for the effects of passive training on sensorimotor cortical representation: A study with functional magnetic resonance imaging in healthy subjects

Repetitive passive movements are part of most rehabilitation procedures, es pecially in patients with stroke and motor deficit. However, little is know n about the consequences of repeated proprioceptive stimulations on the int racerebral sensorimotor network in humans. Twelve healthy subjects were enr olled, and all underwent two functional magnetic resonance imaging (fMRI) s essions separated by a 1-month interval. Passive daily movement training wa s performed in six subjects during the time between the two fMRI sessions. The other six subjects had no training and were considered as the control g roup. The task used during fMRI was calibrated repetitive passive flexion-e xtension of the wrist similar to those performed during training. The contr ol task was rest. The darn were analyzed with SPM96 software. Images were r ealigned, smoothed, and put into Talairach's neuroanatomical space. The tim e effect from the repetition of the task was assessed in the control group by comparing activation versus rest in the second session with activation v ersus rest in the first session. This lime effect then was used as null hyp othesis to assess the training effect alone in our trained group. Passive m ovements compared with rest showed activation of most of the cortical areas involved in motor control (i.e., contralateral primary sensorimotor cortex , supplementary motor area [SMA], cinguium, Brodmann area 40 ipsilateral ce rebellum). Time effect comparison showed a decreased activity of the primar y sensorimotor cortex and SMA anti an increased activity of ipsilateral cer ebellar hemisphere, compatible with a habituation effect. Training brought about an increased activity of contralateral primary sensorimotor cortex an d SMA. A redistribution of SMA activity was observed. The authors demonstra ted that passive training with repeated proprioceptive stimulation induces a reorganization of sensorimotor representation in healthy subjects. These changes take place in cortical areas involved in motor preparation and moto r execution and represent the neural basis of proprioceptive training, whic h might benefit patients undergoing rehabilitative procedures.