Abstract
IntroductionMirror therapy has been shown to be effective in promoting hemiplegic arm recovery in patients with stroke or unilateral cerebral palsy. This study aimed to explore the cortical mapping associated with mirror therapy in a group of healthy adults by using functional near‐infrared spectroscopy.MethodsFifteen right‐handed healthy adults were recruited by means of convenience sampling. A 2 × 2 factorial design was used: movement complexity with two levels—task‐based (T) and movement‐based (M), and visual direction with two levels—mirror visual feedback task (MT) and covered mirror with normal visual feedback task (NoT) as the control, constituting four conditions, namely TMT, MMT, TNoT, and MNoT. The regions of interest were the sensorimotor cortex (SMC), the supplementary motor area (SMA), the superior parietal cortex (SPL), and the precuneus in both the contralateral and ipsilateral hemispheres.ResultsOur findings showed that in the ipsilateral hemisphere, MT induced a higher activation in the SMA and SPL than NoT. With regard to the activation of the ipsilateral SMC, only one channel was found showing superior effects of MT compared with NoT. In addition, MT can strengthen the functional connectivity between the SMC and SMA. In the contralateral hemisphere, both movement complexity and visual direction showed significant main effects in the SMC, while only movement complexity showed a significant main effect in the SMA and SPL. The precuneus of both sides was deactivated and showed no significant difference among the four conditions.ConclusionsOur experiment implies that the modest activation of ipsilateral SMC during MT is likely to be associated with the enhanced activity of ipsilateral SMA and that the precuneus may not be an essential component of the MT‐related neural network.
Highlights
Mirror therapy has been shown to be effective in promoting hemiplegic arm recovery in patients with stroke or unilateral cerebral palsy
We investigated the cortical activation of mirror visual feedback task (MT) with motor tasks of different complexities in a group of healthy adults using functional near-infrared spectroscopy (fNIRS)
In a recent fNIRS study, 3D T1-weighted MRI was used for the anatomical location of NIRS channels (Inagaki et al, 2019), and researchers found that mirror visual feedback applied in unilateral hand movement could induce higher activation in the postcentral gyrus but not in the precentral gyrus
Summary
Mirror therapy has been shown to be effective in promoting hemiplegic arm recovery in patients with stroke or unilateral cerebral palsy. Attention toward the untrained side (i.e., affected arm in patients with stroke) can be increased due to the produced perceptual conflict between the visual feedback and the kinesthetic feedback This latter hypothesis was supported by many studies showing increased activation in the cortical attention system, including the posterior cingulate cortex, insular cortex, superior parietal cortex (SPL), and the precuneus (Deconinck et al, 2015). To perform movements with incongruent (i.e., mirrored) visual feedback is attention demanding; we expected to see a change in precuneus activity during MT It was not consistently shown across fMRI studies that the activation of the supplementary motor area (SMA), which is related to the motor planning of self-initiated movement and the learning of complicated motor skills, can be induced by MT (Matthys et al, 2009; Nachev, Kennard, & Husain, 2008; Shinoura et al, 2008)
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