title: Locomotor training improves reciprocal and nonreciprocal inhibitory control of soleus motoneurons in human spinal cord injury.
abstract: Pathologic reorganization of spinal networks and activity-dependent plasticity are common neuronal adaptations after spinal cord injury (SCI) in humans. In this work, we examined changes of reciprocal Ia and nonreciprocal Ib inhibition after locomotor training in 16 people with chronic SCI. The soleus H-reflex depression following common peroneal nerve (CPN) and medial gastrocnemius (MG) nerve stimulation at short conditioning-test (C-T) intervals was assessed before and after training in the seated position and during stepping. The conditioned H reflexes were normalized to the unconditioned H reflex recorded during seated. During stepping, both H reflexes were normalized to the maximal M wave evoked at each bin of the step cycle. In the seated position, locomotor training replaced reciprocal facilitation with reciprocal inhibition in all subjects, and Ib facilitation was replaced by Ib inhibition in 13 out of 14 subjects. During stepping, reciprocal inhibition was decreased at early stance and increased at midswing in American Spinal Injury Association Impairment Scale C (AIS C) and was decreased at midstance and midswing phases in AIS D after training. Ib inhibition was decreased at early swing and increased at late swing in AIS C and was decreased at early stance phase in AIS D after training. The results of this study support that locomotor training alters postsynaptic actions of Ia and Ib inhibitory interneurons on soleus motoneurons at rest and during stepping and that such changes occur in cases with limited or absent supraspinal inputs.
authors.affiliation: Sensory Motor Performance Program, Rehabilitation Institute of Chicago, Chicago, Illinois; Department of Physical Medicine and Rehabilitation, Northwestern University Feinberg Medical School, Chicago, Illinois; Graduate Center/The City University of New York, New York, New York; and Department of Physical Therapy, College of Staten Island, Staten Island, New York Maria.Knikou@csi.cuny.edu m-knikou@northwestern.edu.
authors.forename: Maria
authors.identifier: http://orcid.org/0000-0002-6277-236X
authors.initials: M
authors.lastname: Knikou
authors.affiliation: Northwestern University Interdepartmental Neuroscience Program, Chicago, Illinois;
authors.forename: Andrew C
authors.initials: AC
authors.lastname: Smith
authors.affiliation: Sensory Motor Performance Program, Rehabilitation Institute of Chicago, Chicago, Illinois;
authors.forename: Chaithanya K
authors.initials: CK
authors.lastname: Mummidisetty
mesh_terms: D000328:Adult; D004558:Electric Stimulation; D004576:Electromyography; D005081:Exercise Therapy; D005260:Female; D006181:H-Reflex; D006801:Humans; D008297:Male; D008875:Middle Aged; D009043:Motor Activity; D009046:Motor Neurons / Q000502:physiology*; D018482:Muscle, Skeletal / Q000294:innervation / Q000503:physiopathology; D009433:Neural Inhibition; D010525:Peripheral Nerves / Q000503:physiopathology; D013119:Spinal Cord Injuries / Q000503:physiopathology* / Q000628:therapy; D055815:Young Adult
keywords: Ib inhibition; locomotor training; neuromodulation; neuroplasticity; reciprocal inhibition; spinal cord injury