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Introduction/Background Motor imagery (MI) has emerged as a promising technique for promoting neuroplasticity and recovery of motor function after a stroke. It is used as an alternative to movement execution (ME). The brain structures involved in MI are largely documented but the existent functional connectivity (FC) during MI and the differences with ME in stroke patients remain underinvestigated. Functional magnetic resonance imaging (fMRI) techniques have the potential to reveal these changes. We aimed to investigate the FC during MI and ME and correlate FC measures between sensorimotor (SMN) regions with motor function of stroke patients. Material and method Twenty-four stroke patients with hemiparesis (time post-stroke = 10 ± 21 months; Upper-limb Fugl-Meyer Score (FMS) = 27.2 ± 13.5/66) were included. The patients underwent fMRI examination while they either imagined or executed wrist extension with their affected hand (AH). We studied FC using seed-to-voxels analysis. We compared the FC of SMN regions between MI and ME of AH movement. Additionally, correlations among brain FC measures and behavioral scores of motor function (FMS) were computed. Results During MI of the AH in comparison with ME, FC of the ipsilesional SMN (BA 40) was decreased with the ipsilesional somatosensory cortex (BA 2, 40, 5) and the cerebellum. In parallel, it was increased with the bilateral frontal cortex (BA 8, 10) ( Fig. 1 ). Besides this, correlation analyses with the FMS revealed that during MI, more impaired patients relied more on functional connections between contralasional BA4 and cerebellum (crus 1 and 2) than less impaired patients did. Conclusion The connectivity changes observed may reveal compensatory networks for MI implicating more the frontal lobe and the contralesional hemisphere in most impaired patients. These results characterized the connectivity patterns of ME and MI and may provide new insights into the neural mechanism underlying them.

Introduction/Background Paired associative stimulation (PAS) is a non-invasive brain stimulation method that modulate cortical plasticity. Motor imagery (MI) can be used as an alternative to movement execution (ME) after stroke. In this study, we want to compare the motor and electrophysiological effects of a session combining PAS and MI exercises to sessions where only one of the intervention was delivered. Material and method MIPAS is a prospective, randomized, cross-over study. Twenty-three stroke patients with hemiparesis (mean age = 52 ± 13 years; time post-stroke = 10 ± 22 months; Upper-limb Fugl-Meyer Score (FMS) = 28 ± 13/66; Kinesthetic and Visual Imagery score (KVIQ_S) = 119 ± 23/140) were included and randomely assigned to one of the three 15 minutes session: PAS + MI; PAS; placebo PAS + MI. The PAS intervention consists of a combination of electrical stimulation of the hemiplegic Extensor Carpi Radialis (ECR) with cortical magnetic stimulation of the ECR cortical representation. In MI condition, the patient is instructed to imagine extension of his hemiplegic wrist and in Placebo PAS intervention, we used a sham probe. We compared the surface variation of the Motor Evoked Potential (MEP) of the ECR and the amplitude of Active Extension (AE) of the hemiplegic side after each session. Results In comparison with the other two sessions, significant facilitation associated with motor improvement was observed 15′ after the end of session placebo PAS + MI (ΔPEM(C) = +62% ± 96.7%; ΔEA(C) = +2.9 ± 6.7°). Significant motor improvement were observed after the sessions PAS + MI and PAS (ΔEA(A) = 4.1 ± 8.1°; ΔEA(B) = 5.4 ± 6.1°) but not association with cortical excitability changes. The motor improvement after the session PAS was significantly higher in comparison with that observed after session placebo PAS + MI. Conclusion Only the session Placebo PAS + MI seems to induce increased cortical excitability associated with motor improvement, the other sessions inducing only motor effect.

Objectives Transcranial magnetic stimulations (TMS) have been used for many years as a diagnostic tool to explore changes in cortical excitability, and more recently as a tool for therapeutic neuromodulation. We are interested in their applications following brain injury: stroke, traumatic and anoxic brain injury. Data synthesis Following brain injury, there is decreased cortical excitability and changes in interhemispheric interactions depending on the type, the severity, and the time-lapse between the injury and the treatment implemented. rTMS (repetitive TMS) is a therapeutic neuromodulation tool which restores the interhemispheric interactions following stroke by inhibiting the healthy cortex with frequencies ≤ 1 Hz, or by exciting the lesioned cortex with frequencies between 3 and 50 Hz. Results in motor recovery are promising and those in improving aphasia or visuospatial neglect are also encouraging. Finally, the use of TMS is mainly limited by the risk of seizure, and is therefore contraindicated for many patients. Conclusion TMS is a useful non-invasive brain stimulation tool to diagnose the effects of brain injury, to study the mechanisms of recovery and a non-invasive neuromodulation promising tool to influence the post-lesional recovery.

Objectives The Paired Associative Stimulation (PAS) is a non-invasive brain stimulation technique combining an electrical peripheral stimulation and a magnetic cortical stimulation. Applied on the wrist extensor muscles, one session induced changes in cortical excitability. We studied the effects of a repetition of 5 PAS sessions against placebo. Material and methods This is a prospective, randomized, double-blind against placebo study. One session consisted in applying an electrical peripheral stimulation on the wrist extensor muscle followed by a 25-ms later magnetic cortical stimulation over the wrist area, at a 0.1-Hz frequency during 30 minutes, the patient receiving 180 paired stimuli. In the SHAM group, the patient received the electrical peripheral stimulation and a SHAM magnetic stimulation. One session was applied every day during 5 days. The changes in area of the motor-evoked potential (MEP), reflecting the changes in cortical excitability, and motor changes studied by the Fugl-Meyer score were assessed at the end of the 1st and 5th session, 3, 5 and 7 days after the end of the 5 days session. Results Twenty-eight patients were included (19 men, mean age: 49.9 ± 13.5 years), with stroke from 10.0 ± 5.1 weeks. Only data from 24 patients were exploitable, 13 patients being included in the PAS group. It was not found significant differences between the two groups regardless of the time after stimulation, or the electrophysiological parameters, neither the motor scores. However, there is a greater MEP variability in the PAS group compared to the SHAM group. All patients ( n = 5) for which PAS increased cortical excitability (D8-MEP > +200% D1-MEP) were those with a low initial level of cortical excitability. Discussion The initial level of cortical excitability seems to play a key role of repeated sessions of PAS on the lasting effects on brain plasticity. Our results confirm the importance of the initial level of neuronal activation in the cortical modulation induced by TMS.

Objective Motor imagery (MI) is a cognitive process of imagining a movement without actually doing it. This technique has demonstrated its benefits in the rehabilitation of hemiplegic patients. Non-invasive brain stimulation (NIBS) is still at a preclinical stage but has demonstrated their adjunct effect in the learning of a motor task. In this study, we studied the motor and electrophysiological effects of a session combining Paired Associative Stimulation (PAS), a technique of NIBS and MI exercises (PAS-MI). Methods A prospective, randomized cross-over study where six patients were included (4 men, age = 44.5 ± 13.7 years; 5.7 ± 7.7 months post-stroke). They randomly underwent three 15-minute sessions of stimulation, one week apart: PAS-MI, PAS alone and ShamPAS associated with MI exercises (ShamPAS-MI). The PAS intervention consisted in an electrical stimulation of the hemiplegic extensor carpi radialis (ECR) associated with cortical magnetic stimulation over the wrist motor area. In MI condition, the patient was instructed to imagine extension of his hemiplegic wrist and in ShamPAS intervention, we used a SHAM probe. We compared the surface variation of the motor-evoked potential (MEP) of the ECR and the amplitude of active extension (AE) of the hemiplegic side obtained after each session. Results Twenty-five minutes after the end of session PAS alone, an increase of MEP surface (+91% ± 150.3%) which reveals a higher cortical excitability associated with a slight motor improvement (ΔEA = 1.33 ± 3.14°) was shown. A smaller facilitation was shown after sessions PAS-MI and ShamPAS-MI (+45.97 ± 134.32% and 44.85 ± 28.77%, respectively) and, in these cases, was not associated with motor improvement. Conclusion The session PAS alone seems to induce motor improvement associated with increased cortical excitability not shown after the other two sessions. The combination of two types of stimuli seems to have less effect, perhaps because of the mechanisms regulating the homeostasis of brain plasticity. The results have to be confirmed on a larger sample.