Alternative Motor Task-Based Pattern Training With a Digital Mirror Therapy System Enhances Sensorimotor Signal Rhythms Post-stroke

Abstract

Mirror therapy (MT) facilitates motor learning and induces cortical reorganization and motor recovery from stroke. We applied the new digital mirror therapy (DMT) system to compare the cortical activation under the three visual feedback conditions: (1) no mirror visual feedback (NoMVF), (2) bilateral synchronized task-based mirror visual feedback training (BMVF), and (3) reciprocal task-based mirror visual feedback training (RMVF). During DMT, EEG recordings, including time-dependent event-related desynchronization (ERD) signal amplitude in both mu and beta bands, were obtained from the standard C3 (ispilesional hemisphere, IH), C4 (contralesional hemisphere, CH), and Cz scalp sites (supplementary motor area, SMA). The entire ERD curve was separated into three time-phases: P0 (-2 to 0 s), P1 (0 to 2 s), and P2 (2 to 4 s). Four-way and subsequent repeated-measures analyses of variance were used to examine the effects of group (stroke vs. control group), test condition (NoMVF, BMVF, and RMVF), time-phase (P0, P1, and P2), and brain area (IH, CH, SMA) on the ERD areas (%) in mu and beta bands. For the mu band, generally, ERD areas (%) were larger in the control than in the stroke group. The ERD areas (%) were largest under the RMVF condition, followed by BMVF and NoMVF conditions. Similar results were found in the beta bands. The main effects of group, time-phase, and test condition on the ERD areas (%) were significant for the three brain areas, except the main effect of group in the SMA (Cz) and CH (C4) brain area. The ERD areas (%) were larger in the control than in the stroke group. The ERD area (%) was significantly larger during P1 than during P0 and P2 (ps < 0.02), and during P2 than during P0 (ps < 0.01). The ERD area (%) under the RMVF condition was significantly larger than that under the BMVF condition and NoMVF condition (ps < 0.05). The present study suggests that cortical activation particularly in the SMA (Cz) of the brain increases in the RMVF condition in both healthy subjects and stroke patients. This result supports the hypothesis that stroke patients may benefit from RMVF training.

Keywords: mirror therapy system; occupational therapy; pattern training; sensorimotor training; stroke therapy.

Copyright © 2019 Chang, Lo, Chen, Lee, Chiang and Li.

Figures

Figure 1

Experimental set up: The DMT system consists of a host personal computer, camera, and therapy table with a movement area and a mirror area. The participant sits behind the table and places a paper cup for task-based training on the mirror area and their non-impaired hand (active hand) on the movement area. In the mirror area of the table, a slim, 27-inch liquid crystal display monitor was situated slightly above the table to reserve the underlying space for the impaired hand as the non-active hand.

Figure 2

Operation process of three test conditions that were used to test their impact on sensorimotor cortical activity. (A) The mirror area showed only a paper cup with a still image of the mirror area without the hand (NoMVF condition). (B) The mirror area showed synchronous, simultaneous mirrored images of the movements of the left hand with bilateral task-based mirror visual feedback (MVF; BMVF condition). (C) The mirrored images of the movements of the left hand were shown in a 2-s delay of the reciprocal action task-based MVF (RMVF condition).

Figure 3

Three-way repeated-measures analysis of variance was used to examine the effects of group, test condition, and time-phase on the event-related desynchronization (ERD) areas (%) in the mu band. (A) There is a statistically significant interaction effect between group and time-phase in the IH brain area (C3). (B) There is a significant interaction effect between the test condition and time-phase in the CH brain area (C4).

Figure 4

Mu band event-related desynchronization (ERD) areas (%) of the control and stroke group (n = 16 each) with error bars (standard deviations) for the three test conditions (NoMVF, BMVF, and delayed RMVF) for the IH (C3), SMA (Cz), and CH (C4) brain areas, respectively. The ERD areas (%) are shown as P0: white, P1: gray, and P2: black; a time-course change in cortical activation can be observed. *,†ERD areas (%) of this test condition are significantly higher than the areas of the previous test condition for the same brain area.

Figure 5

Overall event-related desynchronization (ERD) areas of the control and stroke group (n = 16 each) with error bars (standard deviations) for the three test conditions (NoMVF: white; BMVF: gray, and RMVF: black) for the IH (C3), SMA (Cz), and CH (C4) brain areas, respectively. (A) Overall ERD areas (%) of the mu band (B) Overall ERD areas (%) of the beta band. *,†Overall ERD areas (%) of this test condition are significantly higher than the previous one for the same brain area.

Figure 6

Three-way repeated-measures analysis of variance in the beta band revealed that both test condition and time-phase have main effects in all three brain areas, while group also had a main effect in the IH brain area (C3). Comparison of the mean value of event-related desynchronization (ERD) areas for each main effect are shown for (A) test condition, (B) time-phase, and (C) group. *,†ERD areas (%) of this test condition, time-phase, or group are significantly higher than the previous one in each comparison.