Reduction of Spasticity With Repetitive Transcranial Magnetic Stimulation in Patients With Spinal Cord Injury

Objective. Spasticity with increased tone and spasms is frequent in patients after spinal cord injury (SCI). Damage to descending corticospinal pathways that normally exert spinal segmental control is thought to play an important causal role in spasticity. The authors examined whether the modulation of excitability of the primary motor cortex with highfrequency repetitive transcranial magnetic stimulation (rTMS) could modify lower limb spasticity in patients with incomplete SCI. Methods. Patients were assessed by the Modified Ashworth Scale, Visual Analogue Scale, and the Spinal Cord Injury Spasticity Evaluation Tool (SCI-SET) and neurophysiologically with measures of corticospinal and segmental excitability by the Hmax/Mmax, T reflex, and withdrawal reflex. Fifteen patients received 5 days of daily sessions of active (n = 14) or sham (n = 7) rTMS to the leg motor area (20 trains of 40 pulses at 20 Hz and an intensity of 90% of resting motor threshold for the biceps brachii muscle). Result. A significant clinical improvement in lower limb spasticity was observed in patients following active rTMS but not after sham stimulation. This improvement lasted for at least 1 week following the intervention. Neurophysiological studies did not change. Conclusions. High-frequency rTMS over the leg motor area can improve aspects of spasticity in patients with incomplete SCI.This work was supported in part by grants from the Foundation La Marató TV3 (071931), the Cátedra BBVA (CAT06/023), CNRS UMR 5105 LPNC & INSERM Unit S975-ICM, Paris, France, the FIS (PI082004), and the National Institutes of Health (K24 RR018875 and UL1 RR025758)Medicin

Frontal Non-Invasive Neurostimulation Modulates Antisaccade Preparation in Non-Human Primates

A combination of oculometric measurements, invasive electrophysiological recordings and microstimulation have proven instrumental to study the role of the Frontal Eye Field (FEF) in saccadic activity. We hereby gauged the ability of a non-invasive neurostimulation technology, Transcranial Magnetic Stimulation (TMS), to causally interfere with frontal activity in two macaque rhesus monkeys trained to perform a saccadic antisaccade task. We show that online single pulse TMS significantly modulated antisaccade latencies. Such effects proved dependent on TMS site (effects on FEF but not on an actively stimulated control site), TMS modality (present under active but not sham TMS on the FEF area), TMS intensity (intensities of at least 40% of the TMS machine maximal output required), TMS timing (more robust for pulses delivered at 150 ms than at 100 post target onset) and visual hemifield (relative latency decreases mainly for ipsilateral AS). Our results demonstrate the feasibility of using TMS to causally modulate antisaccade-associated computations in the non-human primate brain and support the use of this approach in monkeys to study brain function and its non-invasive neuromodulation for exploratory and therapeutic purposes

Manipulation of Pre-Target Activity on the Right Frontal Eye Field Enhances Conscious Visual Perception in Humans

The right Frontal Eye Field (FEF) is a region of the human brain, which has been consistently involved in visuo-spatial attention and access to consciousness. Nonetheless, the extent of this cortical site’s ability to influence specific aspects of visual performance remains debated. We hereby manipulated pre-target activity on the right FEF and explored its influence on the detection and categorization of low-contrast near-threshold visual stimuli. Our data show that pre-target frontal neurostimulation has the potential when used alone to induce enhancements of conscious visual detection. More interestingly, when FEF stimulation was combined with visuo-spatial cues, improvements remained present only for trials in which the cue correctly predicted the location of the subsequent target. Our data provide evidence for the causal role of the right FEF pre-target activity in the modulation of human conscious vision and reveal the dependence of such neurostimulatory effects on the state of activity set up by cue validity in the dorsal attentional orienting network

Contributions frontales et pariétales à la perception visuelle humaine

Les aires cérébrales frontales et pariétales sont impliquées dans différents processus cognitifs importants pour la performance visuelle, tels que l'attention ou la conscience. Malgré les preuves existantes en faveur d'une implication de ces régions dans la cognition visuelle, leurs contributions dans le traitement de stimuli non masqués de faible contraste ainsi que l'activité spatio-temporelle sous-tendant ces contributions restent largement inexplorées, tout particulièrement en termes de causalité. Nous avons mené une exploration approfondie de ces contributions chez l'humain, en mettant l'accent sur la dynamique de l'activité neurale et les améliorations perceptives potentielles qui peuvent résulter de la manipulation non invasive de l'activité cérébrale. À cette fin, nous avons testé chez des sujets sains les effets d'impulsions simples ou de rafales courtes de stimulation magnétique transcrânienne (SMT) réelle versus fausse, délivrée sur le champ oculomoteur frontal ou le sillon intrapariétal avant la présentation d'un filtre de Gabor de faible contraste, sur la discrimination et la détection consciente de ce filtre de Gabor. Nos résultats montrent que chez l'humain, la distribution spatio-temporelle de l'activité frontale et pariétale joue un rôle causal dans la performance visuelle. Nos recherches contribuent à mieux comprendre les bases oscillatoires de la cognition visuelle et les comportements associés et à préparer le terrain pour le développement de nouvelles thérapies basées sur la manipulation non-invasive de l'activité cérébrale oscillatoire avec, pour objectif ultime, l'amélioration des pathologies neuropsychiatriques.Frontal and parietal areas have been shown to subtend different cognitive processes such as attentional orienting, decision making and access to consciousness, with bearing on visual performance. In spite of prior evidence supporting an implication of those regions in visual cognition, their contributions to the processing of low-contrast unmasked stimuli and the characteristic spatiotemporal activity patterns underlying them remain to be fully explored and causation is lacking. We here addressed a thorough exploration of such contributions in humans, with an emphasis on the dynamics of neural activity and visual performance enhancements as probed by patterns of noninvasive manipulation of local brain oscillatory activity. To this end, we tested in healthy participants the effects of either single pulses or short bursts of active vs. sham transcranial magnetic stimulation (TMS), delivered to the frontal eye field (FEF) and the intraparietal sulcus (IPS) prior to the presentation of a lateralized low-contrast near-threshold Gabor stimulus, on the visual discrimination and conscious detection of such stimulus. Our findings contribute to better substantiate the oscillatory basis of visual cognition and its associated behaviors and to set the stage for the development of novel therapies based on noninvasive manipulation of dysfunctional brain oscillatory activity.PARIS-JUSSIEU-Bib.électronique (751059901) / SudocSudocFranceF

Motor Cortex Neurostimulation Technologies for Chronic Post-stroke Pain: Implications of Tissue Damage on Stimulation Currents

Background: Central post stroke pain (CPSP) is a highly refractory syndrome that can occur after stroke. Primary motor cortex (M1) brain stimulation using epidural brain stimulation (EBS), transcranial magnetic stimulation (TMS), and transcranial direct current stimulation (tDCS) have been explored as potential therapies for CPSP. These techniques have demonstrated variable clinical efficacy. It is hypothesized that changes in the stimulating currents that are caused by stroke-induced changes in brain tissue conductivity limit the efficacy of these techniques. Methods: We generated MRI-guided finite element models of the current density distributions in the human head and brain with and without chronic focal cortical infarctions during EBS, TMS, and tDCS. We studied the change in the stimulating current density distributions’ magnitude, orientation, and maxima locations between the different models. Results: Changes in electrical properties at stroke boundaries altered the distribution of stimulation currents in magnitude, location, and orientation. Current density magnitude alterations were larger for the non-invasive techniques (i.e., tDCS and TMS) than for EBS. Nonetheless, the lesion also altered currents during EBS. The spatial shift of peak current density, relative to the size of the stimulation source, was largest for EBS. Conclusion: In order to maximize therapeutic efficiency, neurostimulation trials need to account for the impact of anatomically disrupted neural tissues on the location, orientation, and magnitude of exogenously applied currents. The relative current-neuronal structure should be considered when planning stimulation treatment, especially across techniques (e.g., using TMS to predict EBS response). We postulate that the effects of altered tissue properties in stroke regions may impact stimulation induced analgesic effects and/or lead to highly variable outcomes during brain stimulation treatments in CPSP.National Institutes of Health (U.S.) (Grants (R01-NS33975, R21-NS062317, R21-NS084022, R44-AT008637, and R44NS080632)National Institute of Neurological Disorders and Stroke (U.S.) (Award R44NS080632)National Center for Complementary and Integrative Health (U.S.

La stimulation magnétique trans-crânienne répétitive à basse fréquence (rTMS) au niveau de l'hémisphère gauche est-elle efficace pour la rééducation de la négligence spatiale unilatérale persistante après un AVC ?

International audienc

“I do not feel my hand where I see it”: causal mapping of visuo-proprioceptive integration network in a surgical glioma patient

International audienceA recent tasked-based fMRI study unveiled a network of areas implicated in the process of visuo-proprioceptive integration of the right hand. In this study, we report a case of a patient operated on in awake conditions for a glioblastoma of the left superior parietal lobule. When stimulating a white matter site in the anterior wall of the cavity, the patient spontaneously reported a discrepancy between the visual and proprioceptive perceptions of her right hand. Using several multimodal approaches (axono-cortical evoked potentials, tractography, resting-state functional connectivity), we demonstrated converging support for the hypothesis that tumor-induced plasticity redistributed the left-lateralized network of right-hand visuo-proprioceptive integration towards its right-lateralized homolog