Faculty Collaboration Database

Evidence for force-feedback inhibition in chronic stroke. IEEE Trans Neural Syst Rehabil Eng 2004 Jun;12(2):166-76

Date

06/29/2004

Pubmed ID

15218931

DOI

10.1109/TNSRE.2004.828428

Scopus ID

2-s2.0-2942657963 (requires institutional sign-in at Scopus site)   14 Citations

Abstract

The presence of force-feedback inhibition was explored during reflex responses in five subjects with known incidence of stroke. Using constant velocity stretches, it was previously found that after movement onset, active reflex force progressively increases with increasing joint angle, at a rate proportional to a fractional exponent of the speed of stretch. However, after the reflex force magnitude exceeds a particular level, it begins rolling off until maintaining a steady-state value. The magnitudes of these force plateaus are correlated with the speed of stretch, such that higher movement speeds result in higher steady-state forces. Based upon these previous studies, we hypothesized that force plateau behavior could be explained by a force-feedback inhibitory pathway. To help facilitate an understanding of this stretch reflex force roll off, a simple model representing the elbow reflex pathways was developed. This model contained two separate feedback pathways, one representing the monosynaptic stretch reflex originating from muscle spindle excitation, and another representing force-feedback inhibition arising from force sensitive receptors. It was found that force-feedback inhibition altered the stretch reflex response, resulting in a force response that followed a sigmoidal shape similar to that observed experimentally. Furthermore, simulated reflex responses were highly dependent on force-feedback gain, where predicted reflex force began plateauing at decreasing levels with increases in this force-feedback gain. The parameters from the model fits indicate that the force threshold for force-sensitive receptors is relatively high, suggesting that the inhibition may arise from muscle free nerve endings rather than Golgi tendon organs. The experimental results coupled with the simulations of elbow reflex responses suggest the possibility that after stroke, the effectiveness of force-feedback inhibition may increase to a level that has functional significance. Practical implications of these findings are discussed in relation to muscle weakness commonly associated with stroke.

Author List

Hidler JM, Schmit BD

Author

Brian Schmit PhD Professor in the Biomedical Engineering department at Marquette University

MESH terms used to index this publication - Major topics in bold

Chronic Disease
Computer Simulation
Diagnosis, Computer-Assisted
Elbow Joint
Electromyography
Evidence-Based Medicine
Feedback
Humans
Models, Neurological
Muscle Contraction
Muscle Spasticity
Muscle, Skeletal
Neural Inhibition
Paresis
Reflex
Stress, Mechanical
Stroke