# Probing an increased reliance on reticulospinal motor pathways in chronic hemiparetic stroke with advanced spinal cord functional MRI

> **NIH NIH F31** · NORTHWESTERN UNIVERSITY · 2023 · $43,467

## Abstract

PROJECT SUMMARY/ABSTRACT
Individuals with chronic hemiparetic stroke typically have significant upper extremity motor impairments. These
impairments include “associated reactions” and abnormal “muscle synergies”, characterized by inter- and intra-
limb muscle coactivation patterns, respectively. It has been postulated that these motor impairments are due to
an upregulation of the contralesional cortico-reticulospinal tract (CRST), after stroke-inflicted damage to
corticofugal pathways. Neuroimaging in the brain, including functional magnetic resonance imaging (fMRI) and
electromyography (EMG) studies, have widely substantiated this hypothesis, while leaving a tangible gap
between measures of cortical neural function and skeletal muscle coactivation patterns. To our knowledge,
neural activity in the spinal cord has not been investigated in the context of post-stroke motor impairments.
Therefore, it is critical to integrate advanced fMRI methods in the human spinal cord with EMG techniques to
investigate an increased reliance on the CRST in chronic hemiparetic stroke.
The objectives of this research proposal are to investigate the neural mechanisms of post-stroke motor
impairment and long-term to inform development of more targeted therapeutic interventions. If upregulation of
the CRST is responsible for force generation in the paretic upper extremity, its characteristic bilateral and
unilateral projections would be expected to drive associated reactions when activating the non-paretic hand, and
muscle synergies in the paretic limb when activating the paretic hand. Spinal cord fMRI can provide direct insight
into neural activation and motor pathway use in the human cervical spinal cord. In the proposed project,
participants will perform unilateral isometric hand-grasping tasks; muscle activation will be measured with EMG
and spinal cord neural activity will be measured with fMRI. Aim 1 will investigate the relationship of associated
reactions and the lateralization of spinal cord neural activity. CRST-driven associated reactions are expected to
elicit increased inter-limb muscle coactivation and more bilateral spinal cord neural activation when performing
the task with the non-paretic hand. Aim 2 will investigate the relationship of abnormal motor synergies and the
longitudinal extent of motor activation. Synergies driven by diffuse unilateral CRST projections are expected to
elicit increased intra-limb muscle coactivation and an increased longitudinal extent of spinal cord activation.
To execute this research project, the applicant will gain expertise in the neuropathophysiology of stroke and
EMG, receive mentorship from experts in neuroscience and magnetic resonance imaging, and train in scientific
communication, mentorship, and leadership. Northwestern University’s collaborative medical campus, with
neuroimaging experts and state-of-the art research-dedicated MRI scanners, fosters a complete environment for
scientific training and innovative res...

## Key facts

- **NIH application ID:** 10750576
- **Project number:** 1F31NS134222-01
- **Recipient organization:** NORTHWESTERN UNIVERSITY
- **Principal Investigator:** Kimberly Jiyun Hemmerling
- **Activity code:** F31 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2023
- **Award amount:** $43,467
- **Award type:** 1
- **Project period:** 2023-09-01 → 2025-08-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10750576

## Citation

> US National Institutes of Health, RePORTER application 10750576, Probing an increased reliance on reticulospinal motor pathways in chronic hemiparetic stroke with advanced spinal cord functional MRI (1F31NS134222-01). Retrieved via AI Analytics 2026-05-25 from https://api.ai-analytics.org/grant/nih/10750576. Licensed CC0.

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