Cracking the neural code of human movement.Pearcey, Gregory (PI). Memorial University.
Due to limits in technology, motor unit studies have formerly relied on limited samples of motor units, tasks with limited movement, and focused on muscles chosen for ease of motor unit identification rather than considering their functional roles. The overall goals of this project are: 1) to decode the majority of the motoneuron pool to reveal motor unit recruitment and rate coding strategies across diverse muscle groups, and 2) to examine task-dependent alterations in motor unit recruitment and spike patterns across dynamic motor tasks. Generating an atlas of recruitment and spike patterns across diverse muscle groups and motor tasks will dramatically enhance our understanding of human movement control, with implications for augmentation and repair of movement after injury and/or disease.
The neural control of dorsal neck muscles in non-human primates. Corneil, Brian (PI). Western University.
The muscles of the neck are fundamental for motor control; our eyes and ears are mounted on a mobile head, hence neck muscle recruitment must be coordinated with movement of other body segments for accurate orienting and behaviour in the real world. It has long been recognized that neck muscle anatomy is highly complex, featuring compartmentalizations and sharp heterogeneities in muscle fiber distribution, but we know virtually nothing about the physiological relevance of these complexities. The purpose of this grant is to define neck muscle recruitment synergies, leveraging the unique capabilities of Myomatrix arrays to simultaneously sample motor units within a given muscle and across multiple muscles.
Neuronal mechanisms of circumferential electrical epidural stimulation for motor recovery after spinal cord injury. Frigon, Alain (PI). Université de Sherbrooke.
A promising approach to restore movement after spinal cord injury is to electrically stimulate the spinal cord with electrodes implanted in the epidural space. Despite encouraging results, we do not know the populations and discharge behaviours of neurons within the spinal cord recruited by epidural stimulation. The overall goal of this project is to leverage new technological advances in electrode design, including Myomatrix arrays, and computational analyses to determine how epidural electrical stimulation of the spinal cord recruits and activates populations of interneurons and motoneurons controlling leg muscles. The results will allow us to develop a mechanistic framework to guide the development of epidural electrical stimulation of the spinal cord to restore sensorimotor functions in people with spinal cord injury and other movement disorders.
Accelerator Grants
Quantitative Electrophysiological Analysis in Human Nerve Transfer Surgery.Rice, Charles (PI). St. Joseph’s Hospital.
Nerve transfer surgery is often performed following a peripheral nerve injury in which the odds of spontaneous recovery are unfavorable; however, despite its regular use, little is known about the properties of nascent motor units following nerve transfer surgery. The aim of this project is to use the Myomatrix arrays to quantify the properties of nascent motor units post nerve transfer surgery to better understand the process, timing and definition of reinnervated motor units. Results will provide a greater understanding of the basic properties and neurophysiological characteristics of motor units affected by nerve transfer surgery leading to improved clinical outcomes.
Exploring human motor unit recruitment changes between reciprocal and co-contraction patterns of muscle activity.Scott, Steve (PI). Queen’s University.
Most motor actions involve reciprocal patterns of activity between agonist and antagonist muscle groups, but co-contraction of antagonist muscles is commonly observed when performing difficult or novel motor tasks. While motor units generally follow an orderly recruitment pattern, our hypothesis is that co-contraction will lead to changes in this recruitment order. To test this hypothesis, we will compare motor unit recruitment patterns when resisting applied loads versus voluntarily altering co-contraction levels, in both static and dynamic contexts.
Investigating when, where, why, and how movement preparation occurs in the nervous system.Michaels, Jonathan (PI). York University.
It is generally accepted that movements must be prepared before they can be executed and that longer preparation times lead to faster and more accurate movements. However, it is unclear how much of this preparation relies on neural activity at the spinal cord level. This project investigates how movement preparation operates at the level of the spinal cord using a combination of surface muscle recordings, motor unit recordings, and biomechanical modelling during reaching movements.
Probing the flexibility of supraspinal control of motoneurons innervating forearm muscles.Perich, Matt (PI). University of Montreal.
This project explores the flexibility in the relationships between cortical neurons and the spinal motor units that innervate forearm muscles. We will compare how motor unit recruitment across behaviors of varying complexity to determine how descending inputs from the motor cortex to the spinal cord can rapidly reconfigure patterns of MU recruitment based on behavioral demands.
Harnessing residual voluntary motor units in drop foot syndrome patient for new human-machine interface. Durandau, Guillaume (PI). McGill University
Drop foot syndrome, where patients lose control of ankle flexion, affects 20% to 30% of the stroke population, greatly hindering their mobility. This project aims to create a new human-machine interface by extracting volitional control commands from paretic muscles in stroke patients with drop foot syndrome. For this, we will explore the possibility of recording residual voluntary motor units using the Myomatrix array. We will use this command to drive an ankle neuromusculoskeletal model to estimate voluntary flexion-extension ankle joint torque, creating the base for future robotic assistive solution.
Combined myo-cortical coding of spatial reaching in the rat. Bonizzato, Marco (PI). Polytechnique Montréal.
We seek to study cortical control of spinal circuits for reaching and grasping in the rat. To do so, we codeveloped a robotic platform capable to extend the “single pellet reaching task” by supporting generalized reaches and grasps in a 3D space. We will investigate how activations of neurons in the motor cortex and the spinal cord can couple and decouple as the reaching target changes its position in space.
Evaluating the contribution of female sex hormones in motor unit output. Jakobi, Jennifer (PI). University of British Columbia.
It is difficult to resolve whether motor unit activity differs between males and females when little is understood of ovarian hormones influence on motoneuron output in humans. In this project we will investigate the associations between female sex hormones (estrogen and progesterone), force steadiness, and motoneuron output in pre- and post-menopausal females. To further understanding of motoneuron plasticity and functional output in the female motor system, we will test training-related adaptations in motor unit activity and quantify force steadiness after kinesthetic motor imagery training.
Effects of sex and age on motor unit coordination of extrinsic hand muscles. Paris, Michael (PI). York University.
The digits of the hand display a diversity of function, involving both highly coordinated and independent motor unit control within intrinsic and extrinsic hand muscles. However, our understanding of motor unit control mechanisms of the digits, particularly amongst extrinsic hand muscles, is largely derived from young males, despite well-known sex- and age-related differences in the independent and coordinated control of the fingers. This project aims to explore the coordinated and independent control of motor units of extrinsic agonist and antagonist hand muscles during varied single and multi-finger tasks in young and old males and females.
Enhancing muscle activation via optogenetic stimulation: Reducing fatigue and improving force resolution through natural motor unit recruitment order. Ethier, Christian (PI). Université Laval.
This project tests whether optogenetic nerve stimulation can restore natural motor unit recruitment, reducing muscle fatigue and improving force gradation compared to electrical stimulation. We will optimize viral delivery of high-performance opsins to adult rat motoneurons and use high-density EMG and force recordings to directly compare recruitment patterns and functional outcomes. By addressing key limitations of prior studies, this work will provide critical evidence for the clinical potential of optogenetics in neuromuscular rehabilitation and next-generation neuroprosthetics.