Modulation of Stretch Reflexes of the Finger Flexors by Sensory Feedback From the Proximal Upper Limb Poststroke

• Published in: Journal of neurophysiology Vol. 102; no. 3; pp. 1420 - 1429
• Main Authors: Hoffmann, Gilles, Kamper, Derek G, Kahn, Jennifer H, Rymer, William Z, Schmit, Brian D
• Format: Journal Article
• Language: English
• Published: United States Am Phys Soc 01.09.2009; American Physiological Society
• Subjects: Adult; Aged; Analysis of Variance; Biomechanical Phenomena; Electromyography - methods; Feedback - physiology; Female; Fingers - pathology; Humans; Male; Metacarpophalangeal Joint - physiopathology; Middle Aged; Muscle, Skeletal - physiopathology; Posture - physiology; Reflex, Stretch - physiology; Stroke - pathology; Torque; Upper Extremity - physiopathology
• ISSN: 0022-3077; 1522-1598
• DOI: 10.1152/jn.90950.2008

1 Sensory Motor Performance Program, Rehabilitation Institute of Chicago, Chicago, Illinois; 2 Department of Biomedical Engineering, Illinois Institute of Technology, Chicago, Illinois; 3 Department of Physiology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois; and 4 Department of Biomedical Engineering, Marquette University, Milwaukee, Wisconsin Submitted 21 August 2008; accepted in final form 24 June 2009 Abstract Neural coupling of proximal and distal upper limb segments may have functional implications in the recovery of hemiparesis after stroke. The goal of the present study was to investigate whether the stretch reflex response magnitude of spastic finger flexor muscles poststroke is influenced by sensory input from the shoulder and the elbow and whether reflex coupling of muscles throughout the upper limb is altered in spastic stroke survivors. Through imposed extension of the metacarpophalangeal (MCP) joints, stretch of the relaxed finger flexors of the four fingers was imposed in 10 relaxed stroke subjects under different conditions of proximal sensory input, namely static arm posture (3 different shoulder/elbow postures) and electrical stimulation (surface stimulation of biceps brachii or triceps brachii, or none). Fast (300°/s) imposed stretch elicited stretch reflex flexion torque at the MCP joints and reflex electromyographic (EMG) activity in flexor digitorum superficialis. Both measures were greatest in an arm posture of 90° of elbow flexion and neutral shoulder position. Biceps stimulation resulted in greater MCP stretch reflex flexion torque. Fast imposed stretch also elicited reflex EMG activity in nonstretched heteronymous upper limb muscles, both proximal and distal. These results suggest that in the spastic hemiparetic upper limb poststroke, sensorimotor coupling of proximal and distal upper limb segments is involved in both the increased stretch reflex response of the finger flexors and an increased reflex coupling of heteronymous muscles. Both phenomena may be mediated through changes poststroke in the spinal reflex circuits and/or in the descending influence of supraspinal pathways. Address for reprint requests and other correspondence: G. Hoffmann, Sensory Motor Performance Program, Rehabilitation Institute of Chicago, 345 E. Superior St., Suite 1406, Chicago, IL 60611 (E-mail: g-hoffmann{at}northwestern.edu )