Abstract
Most neuroimaging research in stroke rehabilitation mainly focuses on the neural mechanisms underlying the natural history of post-stroke recovery. However, connectivity mapping from resting-state fMRI is well suited for different neurological conditions and provides a promising method to explore plastic changes for treatment-induced recovery from stroke. We examined the changes in resting-state functional connectivity (RS-FC) of the ipsilesional primary motor cortex (M1) in 10 post-acute stroke patients before and immediately after 4 weeks of robot-assisted bilateral arm therapy (RBAT). Motor performance, functional use of the affected arm, and daily function improved in all participants. Reduced interhemispheric RS-FC between the ipsilesional and contralesional M1 (M1-M1) and the contralesional-lateralized connections were noted before treatment. In contrast, greater M1-M1 functional connectivity and disturbed resting-state networks were observed after RBAT relative to pre-treatment. Increased changes in M1-M1 RS-FC after RBAT were coupled with better motor and functional improvements. Mediation analysis showed the pre-to-post difference in M1-M1 RS-FC was a significant mediator for the relationship between motor and functional recovery. These results show neuroplastic changes and functional recoveries induced by RBAT in post-acute stroke survivors and suggest that interhemispheric functional connectivity in the motor cortex may be a neurobiological marker for recovery after stroke rehabilitation.
Highlights
Resting-state functional magnetic resonance imaging (RS-fMRI) has emerged as a powerful tool for evaluating intrinsic brain connectivity and regional interactions during wakeful rest (Friston, 1994; Raichle and Mintun, 2006; Van Essen et al, 2012)
The paired Wilcoxon test on the Fugl-Meyer Assessment (FMA)-upper limb (FMA-upper limb (UL)) total scores revealed that participants showed significant improvements in levels of motor impairment from pre-treatment to the end of robot-assisted bilateral arm therapy (RBAT) (Z = 2.82, p = 0.005)
Functional Connectivity Results The paired Wilcoxon test on the value of the M1-M1 RS-FC showed that participants had significantly increased M1-M1 functional connectivity from pre-treatment to the end of RBAT (Z = 2.80, p = 0.005)
Summary
Resting-state functional magnetic resonance imaging (RS-fMRI) has emerged as a powerful tool for evaluating intrinsic brain connectivity and regional interactions during wakeful rest (Friston, 1994; Raichle and Mintun, 2006; Van Essen et al, 2012). RS-FC research shows that the functional connectivity between the ipsilesional and the contralesional primary sensorimotor cortex is significantly diminished at the early stage of stroke (Wang et al, 2010; Park et al, 2011; Golestani et al, 2013). Decreased functional connectivity with the ipsilesional primary motor cortex (M1) was found in other brain regions such as the bilateral supplementary motor area (SMA), bilateral secondary somatosensory cortex, bilateral cerebellum, bilateral thalamus, contralesional premotor cortex, and contralesional posterior parietal cortex (Carter et al, 2010; Wang et al, 2010)
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