Virtual reality and motor imagery for early post-stroke rehabilitation

So where is the protocol for this located so all 10 million yearly stroke survivors  can easily find it?

Virtual reality and motor imagery for early post-stroke rehabilitation

• Chi S. Choy,
• Qiang Fang,
• Katrina Neville,
• Bingrui Ding,
• Akshay Kumar,
• Seedahmed S. Mahmoud,
• Xudong Gu,
• Jianming Fu &
• Beth Jelfs 

BioMedical Engineering OnLine volume 22, Article number: 66 (2023) Cite this article

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Abstract

Background

Motor impairment is a common consequence of stroke causing difficulty in independent movement. The first month of post-stroke rehabilitation is the most effective period for recovery. Movement imagination, known as motor imagery, in combination with virtual reality may provide a way for stroke patients with severe motor disabilities to begin rehabilitation.

Methods

The aim of this study is to verify whether motor imagery and virtual reality help to activate stroke patients’ motor cortex. 16 acute/subacute (< 6 months) stroke patients participated in this study. All participants performed motor imagery of basketball shooting which involved the following tasks: listening to audio instruction only, watching a basketball shooting animation in 3D with audio, and also performing motor imagery afterwards. Electroencephalogram (EEG) was recorded for analysis of motor-related features of the brain such as power spectral analysis in the αand β frequency bands and spectral entropy. 18 EEG channels over the motor cortex were used for all stroke patients.

Results

All results are normalised relative to all tasks for each participant. The power spectral densities peak near the α band for all participants and also the β band for some participants. Tasks with instructions during motor imagery generally show greater power spectral peaks. The p-values of the Wilcoxon signed-rank test for band power comparison from the 18 EEG channels between different pairs of tasks show a 0.01 significance of rejecting the band powers being the same for most tasks done by stroke subjects. The motor cortex of most stroke patients is more active when virtual reality is involved during motor imagery as indicated by their respective scalp maps of band power and spectral entropy.

Conclusion

The resulting activation of stroke patient’s motor cortices in this study reveals evidence that it is induced by imagination of movement and virtual reality supports motor imagery. The framework of the current study also provides an efficient way to investigate motor imagery and virtual reality during post-stroke rehabilitation.

Background

Stroke is a brain lesion which generally causes disability and even death [1, 2]. Motor impairment is a common consequence of stroke affecting stroke patients’ ability to live independently [3, 4]. The major mechanism behind post-stroke recovery is neuroplasticity which rewires the neural network of the brain [5, 6]. Early motor rehabilitation is essential to effectively restore motor function of stroke patients because neuroplasticity is most active within the first month post-stroke [2, 6, 7]. Initially, mobility of stroke patients is minimal; often they are not able to instigate any movement [2, 8]. There are six Brunnstrom motor recovery stages (BMRS) which describe different levels of mobility[2]. Stroke patients who cannot initiate any movement from affected body parts are classified in stage 1 of the BMRS [2]. Conventional post-stroke rehabilitation that relies on physical movement may be ineffective during the early stage of post-stroke motor recovery because stroke patients are often severely paralysed and unable to participate in physical rehabilitation [2, 8, 9].

Motor imagery (MI) is the mental representation of a body movement [6]. In MI, a patient is required to mentally rehearse a movement without its physical execution [3, 4]. It was suggested that MI could promote recovery of the lesioned brain areas using functional and other neuronal networks; hence, MI appears to be an effective alternative therapy for early post-stroke motor rehabilitation [5, 7]. However, MI requires training and may be challenging particularly for stroke patients [10].

It was shown that observing an action may activate the motor cortex and promote motor learning; thus, facilitating neural recovery [3, 11]. This is due to the mirror neurons being activated during both action execution and observation [3, 11]. The mirror neuron system assists the observer to imitate an observed action; hence, there may be an overlap between action observation (AO) and the process of performing a physical movement [3, 11]. It was also reported that AO via virtual reality (VR) technology could assist stroke patients to focus on MI tasks by visually simulating real movements within an immersive environment, minimising distractions from the surroundings, thus, potentially reducing the difficulty of conventional MI [10, 12]. VR technology has also been shown to assist stroke patients in a minimally conscious state to perform MI [9]. As a result, combining MI and AO for performing the same movement may enhance activation of the motor cortex and facilitate motor recovery of stroke patients, especially in stage 1 of the BMRS [4, 5, 10]. Despite there being positive evidence of VR-assisted MI in post-stroke rehabilitation, the experimental protocol of different studies is not standardised and involves various VR machineries [8, 10, 12]. The findings of different VR-MI studies are not conclusive though promising.

Physiological measure of MI recorded by electroencephalogram (EEG) provides a relatively accessible and objective way to measure brain signals induced by MI with a high temporal resolution [10, 12,13,14,15,16]. In this study, we apply filters as well as both EEG spectra and entropy analyses to investigate whether MI and VR may help to activate the brain areas responsible for motor functions; thus, potentially promoting motor recovery.

Results

The 18 EEG channels covering the motor brain areas shown in Fig. 5 are considered in computing the periodograms and band powers for stroke patients as movement processes mainly involve the motor cortex [8, 10]. Figure 1 shows all subjects’ epoch-averaged periodograms normalised with respect to the subjects’ own experimental tasks in this study: VOICE, MI after VOICE, VR+MI, and MI after VR, with 1 = the maximum and −1 = the minimum. Table 1 presents the p-values of the Wilcoxon signed-rank test for comparing the α

and β band powers associated with different pairs of tasks performed by the stroke patients. Figures 2 and 3 are, respectively, the normalised α and β

band power scalp maps relative to all classes in Experiment 1 for stroke patients 2 and 3 and in Experiment 2 for stroke patients 8 and 10. Figure 4 shows the spectral entropy scalp maps normalised to all classes in Experiments 1 and 2, respectively.

Table 1 Results of the Wilcoxon signed-ranked test between different tasks in the α

and β

frequency bands from the 18 EEG channels on the motor brain areas of stroke subjects

Full size table

Discussion

The experiments of this study aim to guide participants to mentally perform a basketball shooting movement which they cannot perform physically. Bimanual basketball shooting is selected as the MI task to mimic a sport activity involving the upper limbs. Mentally performing a sport involving both hands may actively promote both hemispheres of the brain to be activated, maximising brain activity of the motor cortex, especially for non-experts [3, 6, 17,18,19,20,21]. An upper limb MI is chosen because a larger area of the motor cortex is activated to control upper limbs, thus has been shown to be more effective in motor function recovery than that of lower limbs [3, 6, 22]. The basketball shooting instruction provided in the current study prompts participants to activate their motor cortex by gradually guiding them to imagine the movement in a few steps. Stroke patients have suffered brain damage, so movement instruction should be relatively straightforward and simulate physical movement as much as possible to make the MI task practical [6, 9, 23,24,25,26,27]. A sport exercise shown via video is used to induce a sense of embodiment and self-esteem from the stroke patients by attempting to trigger the neural pathways for motor processes through the patients’ imagination of performing a physical task that appears to be impossible [6, 8, 17, 18, 21, 28,29,30]. The activation intensity distribution of the brain can be studied by power spectral density (PSD), band power and spectral entropy of the EEG data that have been preprocessed [8, 31,32,33].

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