Non-uniform upregulation of the autogenic stretch reflex among hindlimb extensors following lateral spinal lesion in the cat

• Published in: Experimental brain research Vol. 239; no. 9; pp. 2679 - 2691
• Main Authors: Kajtaz, E., Montgomery, L. R., McMurtry, S., Howland, D. R., Nichols, T. Richard
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01-09-2021; Springer; Springer Nature B.V
• Subjects: Animals; Biomedical and Life Sciences; Biomedicine; Body temperature; Brain research; Cats; Complications and side effects; Decerebrate State; Excitability; Extremities (Anatomy); Feedback; Health aspects; Hindlimb; Medical research; Muscle, Skeletal; Muscles; Neurology; Neurosciences; Physiological aspects; Physiological research; Propagation; Proprioception; Reflex; Reflex, Stretch; Reflexes; Research Article; Spinal Cord Injuries; Stretch (Physiology); Stretch reflex; Surgery; Thorax; Up-Regulation; United States; Length feedback; Ia pathway; Extensor muscles; Hemisection
• ISSN: 0014-4819; 1432-1106
• DOI: 10.1007/s00221-020-06016-1

Successful propagation throughout the step cycle is contingent on adequate regulation of whole-limb stiffness by proprioceptive feedback. Following spinal cord injury (SCI), there are changes in the strength and organization of proprioceptive feedback that can result in altered joint stiffness. In this study, we measured changes in autogenic feedback of five hindlimb extensor muscles following chronic low thoracic lateral hemisection (LSH) in decerebrate cats. We present three features of the autogenic stretch reflex obtained using a mechanographic method. Stiffness was a measure of the resistance to stretch during the length change. The dynamic index documented the extent of adaptation or increase of the force response during the hold phase, and the impulse measured the integral of the response from initiation of a stretch to the return to the initial length. The changes took the form of variable and transient increases in the stiffness of vastus (VASTI) group, soleus (SOL), and flexor hallucis longus (FHL), and either increased (VASTI) or decreased adaptation (GAS and PLANT). The stiffness of the gastrocnemius group (GAS) was also variable over time but remained elevated at the final time point. An unexpected finding was that these effects were observed bilaterally. Potential reasons for this finding and possible sources of increased excitability to this muscle group are discussed.