Heteronymous Ia-afferent connections in the upper limb following stroke

• Published in: Muscle & nerve Vol. 41; no. 1; pp. 71 - 77
• Main Authors: Lewis, Gwyn N., McNair, Peter J.
• Format: Journal Article
• Language: English
• Published: Hoboken Wiley Subscription Services, Inc., A Wiley Company 01.01.2010; Wiley
• Subjects: Adult; Afferent Pathways - physiopathology; Aged; Aged, 80 and over; Biological and medical sciences; Electromyography; Female; Follow-Up Studies; Fundamental and applied biological sciences. Psychology; Hand - innervation; Hand - physiopathology; hemiparesis; heteronymous pathway; Humans; Ia afferent; Male; Medical sciences; Middle Aged; Motor control and motor pathways. Reflexes. Control centers of vegetative functions. Vestibular system and equilibration; Muscle Contraction - physiology; Muscle, Skeletal - innervation; Muscle, Skeletal - physiopathology; Neurology; Neurons, Afferent - physiology; Reflex - physiology; stretch reflex; Stroke - diagnosis; Stroke - physiopathology; upper limb; Vascular diseases and vascular malformations of the nervous system; Vertebrates: nervous system and sense organs; Human; Hemiparesis; Nervous system diseases; Stroke; Stretch reflex; Prevalence; Motor system disorder; Excitability; Cardiovascular disease; ia afferent; Flexor carpi radialis muscle; Cerebral disorder; Vascular disease; Coactivation; Chronic; Biceps brachii muscle; Central nervous system disease; Body movement; Upper limb; Neurological disorder; Cerebrovascular disease; heteronymous pathway; Tendon
• ISSN: 0148-639X; 1097-4598; 1097-4598
• DOI: 10.1002/mus.21444

Synergistic arm movement patterns are common following stroke and may arise through enhanced spinally mediated reflex connections between muscles. Our goal was to investigate the excitability of heteronymous Ia‐afferent pathways in people with chronic stroke. Responses to tendon taps of the flexor carpi radialis (FCR) muscle were recorded in FCR, biceps brachii (BB), and middle deltoid (MD) of 13 people with stroke and 13 controls. Heteronymous reflexes were elicited in BB and MD in some, but not all, stroke and control subjects. The prevalence and size of the heteronymous responses were not significantly different between groups. Homonymous reflex responses in FCR were significantly larger in the stroke group. We found that the excitability of heteronymous Ia‐mediated pathways from FCR to BB and MD muscles is not enhanced following stroke, despite exaggerated homonymous reflexes, and they are therefore not likely to contribute to coactivation of forearm and more proximal upper limb muscles. Muscle Nerve, 2010