Abstract
Mirror visual feedback (MVF) is a promising approach to enhance motor performance without training in healthy adults as well as in patients with focal brain lesions. There is preliminary evidence that a functional modulation within and between primary motor cortices as assessed with transcranial magnetic stimulation (TMS) might be one candidate mechanism mediating the observed behavioral effects. Recently, studies using task-based functional magnetic resonance imaging (fMRI) have indicated that MVF-induced functional changes might not be restricted to the primary motor cortex (M1) but also include higher order regions responsible for perceptual-motor coordination and visual attention. However, aside from these instantaneous task-induced brain changes, little is known about learning-related neuroplasticity induced by MVF. Thus, in the present study, we assessed MVF-induced functional network plasticity with resting-state fMRI (rs-fMRI). We performed rs-fMRI of 35 right-handed, healthy adults before and after performing a complex ball-rotation task. The primary outcome measure was the performance improvement of the untrained left hand (LH) before and after right hand (RH) training with MVF (mirror group [MG], n = 17) or without MVF (control group [CG], n = 18). Behaviorally, the MG showed superior performance improvements of the untrained LH. In resting-state functional connectivity (rs-FC), an interaction analysis between groups showed changes in left visual cortex (V1, V2) revealing an increase of centrality in the MG. Within group comparisons showed further functional alterations in bilateral primary sensorimotor cortex (SM1), left V4 and left anterior intraparietal sulcus (aIP) in the MG, only. Importantly, a correlation analysis revealed a linear positive relationship between MVF-induced improvements of the untrained LH and functional alterations in left SM1. Our results suggest that MVF-induced performance improvements are associated with functional learning-related brain plasticity and have identified additional target regions for non-invasive brain stimulation techniques, a finding of potential interest for neurorehabilitation.
Highlights
Behavioral Findings of Mirror Visual FeedbackMotor recovery after stroke depends on the intrinsic properties of the central nervous system to reorganize its structure, function and connections
In line with our hypotheses, we observed superior performance improvements in mirror group (MG) compared to control group (CG)
By taking a closer look at the underlying modifications in Resting-state functional connectivity (rs-FC) within each group via paired t-tests, we found a significant increase in centrality in MG in bilateral SM1 and left V4 and a non-significant trend towards an increase in left premotor cortex (PMC) ipsilateral to the untrained left hand (LH)
Summary
Behavioral Findings of Mirror Visual FeedbackMotor recovery after stroke depends on the intrinsic properties of the central nervous system to reorganize its structure, function and connections. It is known that to some extent, unilateral skill training results in performance gains of both the trained and untrained limb (Obayashi, 2004; Perez et al, 2007; Kwon et al, 2013) In the literature, this phenomenon called intermanual transfer, has been described for multiple motor tasks, like strength training (Carroll et al, 2006), sequential pinch force tasks (Camus et al, 2009) and reaching movements (Criscimagna-Hemminger et al, 2003). This phenomenon called intermanual transfer, has been described for multiple motor tasks, like strength training (Carroll et al, 2006), sequential pinch force tasks (Camus et al, 2009) and reaching movements (Criscimagna-Hemminger et al, 2003) It seems to be influenced by several factors, like structural integrity of the corpus callosum or complexity of the task (Bonzano et al, 2011). Neural mechanisms underlying intermanual transfer seem to be divergent from those mediating MVF-induced performance improvements (Nojima et al, 2012, 2013) and further studies are needed to distinguish these mechanisms/phenomena
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