Recovery of reaching and grasping ability is a crucial function to recover from cervical spinal cord injury (SCI). Epidural electrical stimulation (EES) has shown promising results in improving limbs motor control after SCI in various animal models and in humans. In particular, spatiotemporal alternation of stimulation bursts during movement restored skilled locomotion in rats and Rhesus monkeys with SCI. By mimicking spinal segments activation patterns, these refined stimulation protocols could be pivotal also for the recovery of functional reaching and grasping movements. Indeed, skilled arm control requires complex coordinated activations of multiple arm/hand muscles that might be difficult to achieve with simple continuous stimulation protocols. Here we studied the activation patterns of motorpools in the cervical spinal cord during a reaching and grasping task in primates, for the design of spatiotemporal cervical epidural stimulation protocols. Based on such activation maps we propose a simple spatiotemporal stimulation protocol mimicking the natural synergistic muscle activation during upper limb movements.
Non‐invasive reversible perturbation techniques of brain output such as continuous theta burst stimulation (cTBS), commonly used to modulate cortical excitability in humans, allow investigation of possible roles in functional recovery played by distinct intact cortical areas following stroke. To evaluate the potential of cTBS, the behavioural effects of this non‐invasive transient perturbation of the hand representation of the primary motor cortex (M1) in non‐human primates (two adult macaques) were compared with an invasive focal transient inactivation based on intracortical microinfusion of GABA‐A agonist muscimol. The effects on the contralateral arm produced by cTBS or muscimol were directly compared based on a manual dexterity task performed by the monkeys, the “reach and grasp” drawer task, allowing quantitative assessment of the grip force produced between the thumb and index finger and exerted on the drawer's knob. cTBS only induced modest to moderate behavioural effects, with substantial variability on manual dexterity whereas the intracortical muscimol microinfusion completely impaired manual dexterity, producing a strong and clear cortical inhibition of the M1 hand area. In contrast, cTBS induced mixed inhibitory and facilitatory/excitatory perturbations of M1, though with predominant inhibition. Although cTBS impacted on manual dexterity, its effects appear too limited and variable in order to use it as a reliable proof of cortical vicariation mechanism (cortical area replacing another one) underlying functional recovery following a cortical lesion in the motor control domain, in contrast to potent pharmacological block generated by muscimol infusion, whose application is though limited to an animal model such as non‐human primate.
Patients with supernumerary phantom limb report experiencing an additional limb duplicating its physical counterpart, usually following a stroke with sensorimotor disturbances. Here, we report a short‐lasting case of a right upper supernumerary phantom limb with unusual visuomotor features in a healthy participant during a pure Jacksonian motor seizure unexpectedly induced by continuous Theta‐Burst Stimulation over the left primary motor cortex. Electromyographic correlates of the event followed the phenomenological pattern of sudden appearance and brutal dissolution of the phantom, adding credit to the hypothesis that supernumerary phantom limb results from a dynamic resolution of conflictual multimodal information.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.