Brain activity changes associated with treadmill training after stroke

Abstract

Background and purpose: The mechanisms underlying motor recovery after stroke are not fully understood. Several studies used functional MRI longitudinally to relate brain activity changes with performance gains of the upper limb after therapy, but research into training-induced recovery of lower limb function has been relatively neglected thus far.

Methods: We investigated functional reorganization after 4 weeks of treadmill training with partial body weight support in 18 chronic patients (mean age, 59.9+/-13.5 years) with mild to moderate paresis (Motricity Index affected leg: 77.7+/-10.5; range, 9 to 99) and gait impairment (Functional Ambulation Category: 4.4+/-0.6; range, 3 to 5) due to a single subcortical ischemic stroke using repeated 3.0-T functional MRI and an ankle-dorsiflexion paradigm.

Results: Walking endurance improved after training (2-minute timed walking distance: 121.5+/-39.0 versus pre: 105.1+/-38.1 m; P=0.0001). For active movement of the paretic foot versus rest, greater walking endurance correlated with increased brain activity in the bilateral primary sensorimotor cortices, the cingulate motor areas, and the caudate nuclei bilaterally and in the thalamus of the affected hemisphere.

Conclusions: Despite the strong subcortical contributions to gait control, rehabilitation-associated walking improvements are associated with cortical activation changes. This is similar to findings in upper limb rehabilitation with some differences in the involved cortical areas. We observed bihemispheric activation increases with greater recovery both in cortical and subcortical regions with movement of the paretic foot. However, although the dorsal premotor cortex appears to play an important role in recovery of hand movements, evidence for the involvement of this region in lower extremity recovery was not found.

Figures

Figure 1

Mixed effects z-statistics image at the group level showing areas where signal change from baseline to follow-up with movement of the (right) paretic foot versus rest correlated with performance gains after training. A, For active movement. Significant voxels were found in the SMC (I row), the cingulate motor area (II row), and the caudate nucleus (III row) in both the lesioned and unlesioned hemispheres (coronal, sagittal, axial sections) as well as in both thalami (IV row, far left and middle image in axial orientation). B, For passive movement. Significant voxels were identified in the SMC bilaterally in areas that show partial overlap with those defined by the contrasts with active movement. (All results are from clusterbased mixed effects analyses; z >2.3, corrected P=0.05; crosshairs at local maxima specified by MNI coordinates; images shown in radiological convention; left hemisphere=lesioned by the strokes).

Figure 2

Region of interest analyses. Scatterplots with fitted linear regression curves demonstrating the significant correlation between the median signal change from baseline to follow-up with movement of the paretic foot versus rest in the primary SMC and the absolute increase in walking endurance (A, SMCc cluster in the lesioned left hemisphere marked by the arrowhead; (B) SMCi cluster in the unlesioned right hemisphere, marked by the arrowhead).