Inter-individual variation in reciprocal Ia inhibition is dependent on the descending volleys delivered from corticospinal neurons to Ia interneurons

• Published in: Journal of electromyography and kinesiology Vol. 24; no. 1; pp. 46 - 51
• Main Authors: Kubota, Shinji, Uehara, Kazumasa, Morishita, Takuya, Hirano, Masato, Funase, Kozo
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.02.2014
• Subjects: Adult; Conditioning (Psychology) - physiology; Corticospinal tract; Electric Stimulation; Electromyography; H-Reflex - physiology; Humans; Individual variation; Interneurons - physiology; Muscle, Skeletal - innervation; Neural Inhibition - physiology; Neuronal Plasticity - physiology; Neurons - physiology; Physical Medicine and Rehabilitation; Pyramidal Tracts - cytology; Pyramidal Tracts - physiology; Reciprocal Ia inhibition; Reference Values; Spinal cord; Synaptic plasticity; Synaptic Potentials - physiology; Tibial Nerve - physiology; Transcranial Magnetic Stimulation; Young Adult; Spinal cord; Corticospinal tract; Reciprocal Ia inhibition; Individual variation; Synaptic plasticity
• ISSN: 1050-6411; 1873-5711
• DOI: 10.1016/j.jelekin.2013.11.004

Abstract Introduction We investigated the extent to which the corticospinal inputs delivered to Ia inhibitory interneurons influence the strength of disynaptic reciprocal Ia inhibition. Methods Seventeen healthy subjects participated in this study. The degree of reciprocal Ia inhibition was determined via short-latency (condition-test interval: 1–3 ms) suppression of Sol H-reflex by conditioning stimulation of common peroneal nerve. The effect of corticospinal descending inputs on Ia inhibitory interneurons was assessed by evaluating the conditioning effect of transcranial magnetic stimulation (TMS) on the Sol H-reflex. Then, we determined the relationship between the degree of reciprocal Ia inhibition and the conditioning effect of TMS on the Sol H-reflex. Result We found that the degree of reciprocal Ia inhibition and the extent of change in the amplitude of the TMS-conditioned H-reflex, which was measured from short latency facilitation to inhibition, displayed a strong correlation ( r = 0.76, p < 0.01) in the resting conditions. Conclusion The extent of reciprocal Ia inhibition is affected by the corticospinal descending inputs delivered to Ia inhibitory interneurons, which might explain the inter-individual variations in reciprocal Ia inhibition.