More conditioning stimuli enhance synaptic plasticity in the human spinal cord

Siobhan C Fitzpatrick; Billy L Luu; Jane E Butler; Janet L Taylor

doi:10.1016/j.clinph.2015.03.013

More conditioning stimuli enhance synaptic plasticity in the human spinal cord

Clin Neurophysiol. 2016 Jan;127(1):724-731. doi: 10.1016/j.clinph.2015.03.013. Epub 2015 Apr 4.

Authors

Siobhan C Fitzpatrick¹, Billy L Luu², Jane E Butler³, Janet L Taylor⁴

Affiliations

¹ Neuroscience Research Australia, Barker Street, Randwick, NSW, Australia; University of New South Wales, Sydney, NSW, Australia. Electronic address: s.fitzpatrick@neura.edu.au.
² Neuroscience Research Australia, Barker Street, Randwick, NSW, Australia; University of New South Wales, Sydney, NSW, Australia. Electronic address: b.luu@neura.edu.au.
³ Neuroscience Research Australia, Barker Street, Randwick, NSW, Australia; University of New South Wales, Sydney, NSW, Australia. Electronic address: j.butler@neura.edu.au.
⁴ Neuroscience Research Australia, Barker Street, Randwick, NSW, Australia; University of New South Wales, Sydney, NSW, Australia. Electronic address: j.taylor@neura.edu.au.

PMID: 25912336
DOI: 10.1016/j.clinph.2015.03.013

Abstract

Objective: To examine whether more paired corticospinal-motoneuronal stimulation (PCMS) is more effective at inducing spinal level plasticity.

Methods: To produce facilitation, corticospinal volleys evoked by motor cortical transcranial magnetic stimulation (TMS) were timed to arrive at corticospinal-motoneuronal synapses prior to antidromic potentials evoked in motoneurones by electrical brachial plexus stimulation. Paired stimuli were delivered repeatedly. 50-pair conditioning (50-PCMS) was compared to 100 pairs in single block (100-PCMSsingle) and spaced (2 blocks of 50, 15-min break; 100-PCMSspaced) patterns, and to 50 single, unpaired TMS (50-TMS). Biceps responses to cervicomedullary stimulation (cervicomedullary motor evoked potentials, CMEPs) and TMS (motor evoked potentials, MEPs) were measured before and for 1h after conditioning (recorded each 5 min).

Results: After 100-PCMS, average CMEP areas were increased by 46 ± 55% (mean ± SD; n=10; 100-PCMSsingle) and 71 ± 99% (100-PCMSspaced). 50-PCMS produced a non-significant 6 ± 40% increase. After 100-PCMSsingle and 100-PCMSspaced, CMEPs were larger than those after 50-TMS from 0 to 60 min (p<0.05). 100-PCMSsingle and 100-PCMSspaced produced more reliable changes than 50-PCMS. Overall, MEPs were larger at 35-60 min; however there were no differences between conditioning protocols.

Conclusions: More PCMS produces more reliable enhancement of corticospinal transmission.

Significance: This technique has therapeutic potential to improve muscle control in patients with reduced descending drive.

Keywords: Corticospinal; STDP; Spike-timing-dependent plasticity.

Publication types

Randomized Controlled Trial
Research Support, Non-U.S. Gov't

MeSH terms

Adolescent
Adult
Cross-Over Studies
Evoked Potentials, Motor / physiology*
Female
Humans
Male
Neuronal Plasticity / physiology*
Pyramidal Tracts / physiology*
Spinal Cord / physiology*
Transcranial Magnetic Stimulation / methods*
Young Adult