Abstract
Paired associative stimulation (PAS) produces enduring neuroplasticity based on Hebbian associative plasticity. This study established the changes in spinal motoneuronal excitability by pairing transcortical and transspinal stimulation. Transcortical stimulation was delivered after (transspinal-transcortical PAS) or before (transcortical-transspinal PAS) transspinal stimulation. Before and after 40 minutes of each PAS protocol, spinal neural excitability was assessed based on the amplitude of the transspinal-evoked potentials (TEPs) recorded from ankle muscles of both legs at different stimulation intensities (recruitment input-output curve). Changes in TEPs amplitude in response to low-frequency stimulation and paired transspinal stimuli were also established before and after each PAS protocol. TEP recruitment input-output curves revealed a generalized depression of TEPs in most ankle muscles of both legs after both PAS protocols that coincided with an increased gain only after transcortical-transspinal PAS. Transcortical-transspinal PAS increased and transspinal-transcortical PAS decreased the low-frequency-dependent TEP depression, whereas neither PAS protocol affected the TEP depression observed upon paired transspinal stimuli. These findings support the notion that transspinal and transcortical PAS has the ability to alter concomitantly cortical and spinal synaptic activity. Transspinal and transcortical PAS may contribute to the development of rehabilitation strategies in people with bilateral increased motoneuronal excitability due to cortical or spinal lesions.
Highlights
Activity-dependent strengthening of synapses is an important mechanism underlying neural plasticity in both invertebrates and vertebrates [1]
Human corticospinal excitability is affected by paired stimuli delivered to a mixed peripheral nerve of arms or legs and motor cortex based on the timing between the two associative stimuli [2,3,4,5,6,7,8,9]
Neural Plasticity transspinal Paired associative stimulation (PAS)) [17]. These neuromodulatory effects coincided with directional changes of the excitability threshold of muscle spindle primary (Ia) afferents [17]. Based on these strong neuromodulatory effects, in this study we investigated to what extent transspinal and transcortical PAS alters the amplitude of transspinal-evoked potentials (TEPs) recorded from shank muscles of both legs
Summary
Activity-dependent strengthening of synapses is an important mechanism underlying neural plasticity in both invertebrates and vertebrates [1] In this context, human corticospinal excitability is affected by paired stimuli delivered to a mixed peripheral nerve of arms or legs and motor cortex based on the timing between the two associative stimuli [2,3,4,5,6,7,8,9]. Plasticity of cortical, corticospinal, and spinal human neural excitability as a result of paired associative stimulation (PAS) delivered to a mixed peripheral nerve and motor cortex is well established [8, 11,12,13,14,15,16]. Cortical feedback mechanisms remain unaltered, and corticospinal excitability decreases when TMS is delivered before transspinal stimulation
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
