Same Intervention-Different Reorganization: The Impact of Lesion Location on Training-Facilitated Somatosensory Recovery After Stroke

Background. The brain may reorganize to optimize stroke recovery. Yet relatively little is known about neural correlates of training-facilitated recovery, particularly after loss of body sensations. Objective. Our aim was to characterize changes in brain activation following clinically effective touch discrimination training in stroke patients with somatosensory loss after lesions of primary/secondary somatosensory cortices or thalamic/capsular somatosensory regions using functional magnetic resonance imaging (fMRI). Methods. Eleven stroke patients with somatosensory loss, 7 with lesions involving primary (S1) and/or secondary (S2) somatosensory cortex (4 male, 58.7 +/- 13.3 years) and 4 with lesions primarily involving somatosensory thalamus and/or capsular/white matter regions (2 male, 58 +/- 8.6 years) were studied. Clinical and MRI testing occurred at 6 months poststroke (preintervention), and following 15 sessions of clinically effective touch discrimination training (postintervention). Results. Improved touch discrimination of a magnitude similar to previous clinical studies and approaching normal range was found. Patients with thalamic/capsular somatosensory lesions activated preintervention in left ipsilesional supramarginal gyrus, and postintervention in ipsilesional insula and supramarginal gyrus. In contrast, those with S1/S2 lesions did not show common activation preintervention, only deactivation in contralesional superior parietal lobe, including S1, and cingulate cortex postintervention. The S1/S2 group did, however, show significant change over time involving ipsilesional precuneus. This change was greater than for the thalamic/capsular group (P = .012; d = -2.43; CI = -0.67 to -3.76). Conclusion. Different patterns of change in activation are evident following touch discrimination training with thalamic/capsular lesions compared with S1/S2 cortical somatosensory lesions, despite common training and similar improvement.