Abstract
Post-stroke flexion synergy limits arm/hand function and is also linked to hyperactive stretch reflexes or spasticity. It is implicated in the increased role of indirect motor pathways following damage to direct corticospinal projections. We hypothesized that this maladaptive neuroplasticity also affects stretch reflexes. Specifically, multi-synaptic interactions in indirect motor pathways may increase nonlinear neural connectivity and time lag between stretch and reflex muscle response. Continuous position perturbations were applied to the elbow joint when eleven participants with stroke generated two levels of shoulder abduction (SABD) torques with their paretic arm to induce synergy-related spasticity. Likewise, the perturbations were applied to eleven control subjects while performing SABD and elbow flexion levels matching the synergy torques in stroke. We quantified linear and non-linear connectivity and the corresponding time lags between perturbations and muscle activity. Enhanced nonlinear connectivity with a prolonged time lag was found in stroke as compared to controls. Non-linear connectivity and time lag also increased with the expression of the flexion synergy, as induced by greater SABD load levels, in stroke. This study provides new evidence of changes in neural connectivity and long-latency time lag in the stretch reflex response post-stroke. The results suggest the contribution of indirect motor pathways to synergy-related spasticity.
Original language | English (US) |
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Article number | 9058690 |
Pages (from-to) | 1436-1441 |
Number of pages | 6 |
Journal | IEEE Transactions on Neural Systems and Rehabilitation Engineering |
Volume | 28 |
Issue number | 6 |
DOIs | |
State | Published - Jun 2020 |
Funding
Manuscript received September 18, 2019; revised March 12, 2020; accepted April 4, 2020. Date of publication April 7, 2020; date of current version June 5, 2020. The work of Yuan Yang was supported in part by the Northwestern Medicine and Northwestern University Clinical and Translational Sciences Institute, through the Dixon Translational Research Grants Initiative under Grant UL1TR001422 and in part by the NIH under Grant 1R21HD099710. The work of Netta Gurari was supported under Grant K25 HD096116. The work of Julius P. A. Dewald was supported by the NIH under Grant 1R21HD099710, Grant R01HD039343, and Grant R01NS105759. (Corresponding author: Yuan Yang.) Yuan Yang and Netta Gurari are with the Department of Physical Therapy and Human Movement Sciences, Feinberg School of Medicine, Northwestern University, Chicago, IL 60208 USA, and also with the Interdepartmental Neuroscience Program, Northwestern University, Chicago, IL 60208 USA (e-mail: email: [email protected]).
Keywords
- Hemiparetic stroke
- flexion synergy
- neural connectivity
- spasticity
- stretch reflex
- time lag
ASJC Scopus subject areas
- Internal Medicine
- General Neuroscience
- Biomedical Engineering
- Rehabilitation