The neural mechanism of motor imagery training′s motor recovery effects after stroke / 中华物理医学与康复杂志

ABSTRACT

Objective:To explore the mechanism of motor imagery training (MIT) combined with conventional rehabilitation to promote the functional recovery of upper limbs in stroke survivors. To explore the brain network reorganization resulting when motor imagery training (MIT) is combined with conventional rehabilitation to promote the motor recovery of stroke survivors.Methods:Fourteen hemiplegic patients were recruited as the MIT group. They underwent 4 weeks of MIT (30 min/day, 5 days/week) along with conventional rehabilitation treatment. The upper limb section of the Fugl-Meyer assessment (FMA-UE) and the modified Barthel Index (MBI) were used to assess all of the patients, and resting-state fMRI was performed before and after the treatment. Twenty-eight age- and sex-matched healthy subjects also received one-time resting-state fMRI scanning. Granger causal analysis was performed in the MIT group to calculate the changes in effective connection between the ipsilesional primary motor cortex and the whole brain before and after the treatment, and the results were compared with the healthy control group.Results:After the treatment, the average FMA-UE and MBI of the MIT group had increased significantly. Before the intervention, the effective connection mode of the ipsilesional M1 area in the MIT group was significantly different from that of the healthy controls. The causal flow from the ipsilesional M1 area to the bilateral prefrontal cortex had increased abnormally and the causal flow from the contralesional primary motor cortex, the inferior parietal lobule and the cerebellum to the ipsilesional M1 area had decreased significantly. After the treatment, the effective connection pattern of the stroke survivors was nearly normal, and the causal influence from contralesional motor imagery-related brain areas (the superior parietal lobule, inferior parietal lobule, thalamus and the fusiform gyrus) to the ipsilesional M1 area was enhanced. Effective connection from the ipsilesional M1 area to the contralesional cerebellum before the intervention was positively correlated with the improvement in FMA-UE scores, and the effective connection from the contralesional middle frontal gyrus to the ipsilesional M1 area was correlated negatively.Conclusions:The neural mechanism of MIT's effectiveness when it is combined with conventional rehabilitation might be related to the reorganization of effective connections. That would include enhanced causal flow between motor imagery-related brain areas and the contralesional cerebellum and ipsilesional M1 area. Down-regulation of the effective connection from the contralesional middle frontal gyrus to the ipsilesional M1 area also occurs.