Spinal plasticity with motor imagery practice

Abstract

Key points While a consensus has now been reached on the effect of motor imagery (MI) – the mental simulation of an action – on motor cortical areas, less is known about its impact on spinal structures. The current study, using H‐reflex conditioning paradigms, examined the effect of a 20 min MI practice on several spinal mechanisms of the plantar flexor muscles. We observed modulations of spinal presynaptic circuitry while imagining, which was even more pronounced following an acute session of MI practice. We suggested that the small cortical output generated during MI may reach specific spinal circuits and that repeating MI may increase the sensitivity of the spinal cord to its effects. The short‐term plasticity induced by MI practice may include spinal network modulation in addition to cortical reorganization. Abstract Kinesthetic motor imagery (MI) is the mental simulation of a movement with its sensory consequences but without its concomitant execution. While the effect of MI practice on cortical areas is well known, its influence on spinal circuitry remains unclear. Here, we assessed plastic changes in spinal structures following an acute MI practice. Thirteen young healthy participants accomplished two experimental sessions: a 20 min MI training consisting of four blocks of 25 imagined maximal isometric plantar flexions, and a 20 min rest (control session). The level of spinal presynaptic inhibition was assessed by conditioning the triceps surae spinal H‐reflex with two methods: (i) the stimulation of the common peroneal nerve that induced D1 presynaptic inhibition (HPSI response), and (ii) the stimulation of the femoral nerve that induced heteronymous Ia facilitation (HFAC response). We then compared the effects of MI on unconditioned (HTEST) and conditioned (HPSI and HFAC) responses before, immediately after and 10 min after the 20 min session. After resting for 20 min, no changes were observed on the recorded parameters. After MI practice, the amplitude of rest HTEST was unchanged, while HPSI and HFAC significantly increased, showing a reduction of presynaptic inhibition with no impact on the afferent‐motoneuronal synapse. The current results revealed the acute effect of MI practice on baseline spinal presynaptic inhibition, increasing the sensitivity of the spinal circuitry to MI. These findings will help in understanding the mechanisms of neural plasticity following chronic practice.

Gravity highlights a dual role of the insula in internal models

“…Our results showed, regardless of task dynamics, a high temporal correspondence between them. This isochronism extends previous findings that reported comparable durations of actual and mental movements (Gentili et al, 2004;Guillot and Collet, 2005;Papaxanthis et al, 2012) and reinforces the well-documented idea of a similar neurocognitive network between actual and mental states (Grosprêtre et al, 2019;Ruffino et al, 2017). Temporal similarities between actual and mental movements reinforce the idea that the brain preserves an accurate internal model of arm and environmental dynamics.…”

Vibration‐induced depression in spinal loop excitability revisited

“… b ) with an interstimulus interval of 20 ms, reported as the most effective delay to ensure a large inhibitory effect on the conditioned H‐reflex (Grospretre et al . ). Ten conditioned H‐reflexes ( H D1 ) were recorded at 5–10 s intervals for PRE and POST measurements (Fig.…”

“…the lowest intensity that evoked at least three M-waves out of five stimulations (mean M-waves were 0.68 ± 0.36 mV and 0.59 ± 0.33 mV for S H depress and S H match sessions, respectively). Then the SOL H-reflex (using the stimulation intensity determined for H TEST ) was conditioned by a prior stimulation of the fibular nerve (Mizuno et al 1971;Hultborn et al 1987b) with an interstimulus interval of 20 ms, reported as the most effective delay to ensure a large inhibitory effect on the conditioned H-reflex (Grospretre et al 2018). Ten conditioned H-reflexes (H D1 ) were recorded at 5-10 s intervals for PRE and POST measurements ( Fig.…”

Motor Imagery Practice and Cognitive Processes

“…These regions include the supplementary motor area (SMA), premotor cortex (PMC), primary motor cortex (M1), posterior parietal regions (e.g., the inferior and superior parietal lobes), the basal ganglia (BG) and cerebellum (see Hardwick et al, 2018). Furthermore, evidence demonstrates that MIP not only activates motor cortical and subcortical regions but also induces plastic change in motor networks and modulates synaptic activity at the spinal level (e.g., Debarnot et al, 2014;Grosprêtre et al, 2019). Interestingly, the latter effect indicates that motor commands are issued during MI and while they remain subthreshold for physical movement, they have the capacity to influence spinal cord activity (Grosprêtre et al, 2018(Grosprêtre et al, , 2019.…”