Reliability of the TMS-conditioned monosynaptic reflex in the flexor carpi radialis muscle. (6th February 2021)

• Record Type: Journal Article
• Authors: Capozio, Antonio; Chakrabarty, Samit; Astill, Sarah
• Is Part Of: Neuroscience letters. Volume 745(2021)
• Publication Date: 2021-02-06
• Subjects: EF early facilitation -- EMG electromyography -- FCR flexor carpi radialis -- H-reflex Hoffman reflex -- Mmax maximal motor wave -- HM10 % H-reflex at 10 % of Mmax -- ICC intraclass correlation coefficient -- MEP motor evoked potential -- M1 primary motor cortex -- MSO maximum stimulator output -- MT motor threshold -- PNS peripheral nerve stimulation -- TMS transcranial magnetic stimulation; Transcranial magnetic stimulation -- H-reflex -- FCR -- Corticospinal tract -- Reliability; Neurology -- Periodicals; Neurology -- Periodicals; Research -- Periodicals; Neurologie -- Périodiques; Neuroanatomie -- Périodiques; Neuropharmacologie -- Périodiques; Neurophysiologie -- Périodiques; Neurology; Periodicals; Electronic journals; 617.48
• DOI: 10.1016/j.neulet.2020.135622
• Languages: English
• ISSNs: 0304-3940

Abstract

Highlights: TMS pulses increase the amplitude of the FCR H-reflex at multiple conditioning-test intervals. TMS-conditioned H-reflexes exhibit good to excellent reliability over 3 sessions. The highest reliability was observed when the cortical volley reached spinal motoneurons 2 ms before the peripheral volley. The technique can be used to study pathway-specific changes in neural excitability. Abstract: A subthreshold pulse of transcranial magnetic stimulation (TMS) on the motor cortex can modulate the amplitude of the monosynaptic reflex (H-reflex) elicited in the flexor carpi radialis (FCR) muscle, a method known as TMS-conditioning of the H-reflex. The purpose of this study was to establish the intersession reliability of this method over the course of three sessions. Eleven healthy participants received either peripheral nerve stimulation (PNS), TMS or a combination of the two. The intensity of the PNS stimuli was set to evoke a monosynaptic response (H-reflex) corresponding to 10 % of the maximum motor response (Mmax ), HM10 % . The conditioning effect of TMS on the monosynaptic reflex was assessed by delivering subthreshold cortical pulses at different conditioning-test intervals (from -7 ms to 7 ms) from peripheral nerve stimulation. The first interval at which facilitation could be observed was deemed early facilitation (EF). Using intraclass correlation coefficients (ICCs), we found excellent reliability for Mmax amplitudes (ICC = 0.98), HM10 % amplitudes (ICC = 0.85) and TMS-conditioned H-reflexes recorded at the interval following EF (EF + 2 ms) (ICC = 0.87). Good reliability (ICCs ranging from 0.67 to 0.77) was found for the other conditioning-test intervals. We conclude that TMS-conditioned H-reflexes are reliable parameters to assess the excitability of corticospinal circuits.