Biology subjects

Grigsby, E. M.

Publications and source records attributed to Grigsby, E. M..

4 recordsLinked to original sources

bioRxiv2026

Pre-synaptic facilitation of corticospinal output improves dexterity and finemotor control after stroke

The corticospinal tract (CST) is a neural pathway that supports skilled use of the arm and hand. Lesions of corticospinal axons result in muscle weakness, deficits of gross motor function, and loss of proximal and distal dexterous control for which effective treatments are still lacking. Here we exploited excitatory connections from motor thalamus to primary motor cortex to potentiate surviving descending signals and restore volitional arm and hand control in three monkeys with corticospinal tract lesion, using deep brain stimulation. Stimulation targeted to thalamocortical projections facilitated upper-limb movements, enabling monkeys with arm and hand paralysis to perform unconstrained 3D reach and fine dexterous tasks. Stimulation improved strength, hand gross motor function, and digits control. Electrophysiology suggested that effects were mediated by and more effective when targeting fibers with monosynaptic connection to the corticospinal motoneurons. Stimulation was delivered in continuous with FDA-clinically approved parameters holding realistic promises of clinical translation.

neuroscience↗

bioRxiv2024

A posture subspace in primary motor cortex

To generate movements, the brain must combine information about movement goal and body posture. Motor cortex (M1) is a key node for the convergence of these information streams. How are posture and goal information organized within M1s activity to permit the flexible generation of movement commands? To answer this question, we recorded M1 activity while monkeys performed a variety of tasks with the forearm in a range of postures. We found that posture- and goal-related components of neural population activity were separable and resided in nearly orthogonal subspaces. The posture subspace was stable across tasks. Within each task, neural trajectories for each goal had similar shapes across postures. Our results reveal a simpler organization of posture information in M1 than previously recognized. The compartmentalization of posture and goal information might allow the two to be flexibly combined in the service of our broad repertoire of actions.

neuroscience↗

bioRxiv2024

Dynamical constraints on neural population activity

The manner in which neural activity unfolds over time is thought to be central to sensory, motor, and cognitive functions in the brain. Network models have long posited that the brains computations involve time courses of activity that are shaped by the underlying network. A prediction from this view is that the activity time courses should be difficult to violate. We leveraged a brain-computer interface (BCI) to challenge monkeys to violate the naturally-occurring time courses of neural population activity that we observed in motor cortex. This included challenging animals to traverse the natural time course of neural activity in a time-reversed manner. Animals were unable to violate the natural time courses of neural activity when directly challenged to do so. These results provide empirical support for the view that activity time courses observed in the brain indeed reflect the underlying network-level computational mechanisms that they are believed to implement.

neuroscience↗

bioRxiv2023

GABA Increases Sensory Transmission In Monkeys

Sensory input flow is central to voluntary movements. For almost a century, GABA was believed to modulate this flow by inhibiting sensory axons in the spinal cord to sculpt neural inputs into skilled motor output. Instead, here we show that GABA can also facilitate sensory transmission in monkeys and consequently increase spinal and cortical neural responses to sensory inputs challenging our understanding of generation and perception of movement.

neuroscience↗