# Altered Motor Function & Force Feedback After Spinal Cord Injury

> **NIH NIH R01** · UNIVERSITY OF LOUISVILLE · 2020 · $578,717

## Abstract

Extensor muscles of the hind limbs are actively involved in weight support and walking activities.
These muscles are extensively linked by inhibitory, force dependent pathways which contribute
to the successful execution of a range of functional behaviors, including locomotion. These
reflex pathways are thought to arise from Golgi tendon organs and are believed to regulate limb
stiffness and promote inter-joint coordination during movements. Weightings of these linkages
vary across control, decerebrate animals when quiescent, but obey a proximal to distal gradient
during stepping on a treadmill. This finding indicates the strength and distribution of these reflex
pathways are subject to modulation in a task-dependent manner. Our preliminary data in
animals suggest that spinal cord hemisection alters the normal distribution and a dominant
distal-to-proximal inhibitory gradient emerges. Animals with this lesion do not exhibit clasp-knife
inhibition, a phenomenon mediated by receptors other than Golgi tendon organs and that results
from bilateral injury to the dorsal half of the spinal cord. Changes in the strength and distribution
of force feedback that we have observed is correlated with diminished limb stiffness and poor
weight acceptance during locomotor tasks – both of which are problems seen in humans with
spinal cord injuries (SCIs). These findings provide new insight into potential mechanisms
contributing to disruption of motor function following injury. Our guiding hypothesis is: SCI-
induced force-feedback dysregulation results in strong inhibition directed toward
proximal muscles and contributes to inadequate limb stiffness during weight support
phases of movement. The current application has evolved from collaborative work across two
established laboratories, bringing together expertise in SCI, plasticity, force feedback and motor
control. The proposed studies are designed to understand and map changes in force feedback
control following SCI, characterize associated changes in gait subphases where inhibitory force
feedback is thought to be most active across diverse locomotor tasks, and determine which
white matter tracts may modulate spinal circuitry responsible for force feedback. Data
generated in the proposed projects will be compared with an existing laboratory database
containing force feedback findings from control decerebrate preparations. Overall, findings from
these studies will explicate the impact of disrupting this intralimb control system on
performance, provide critical mechanistic insight likely to be essential for design of the most
effective rehabilitation programs for those with SCIs and other neurological disorders, and lay
groundwork for development of a new method for testing force feedback in humans

## Key facts

- **NIH application ID:** 9894867
- **Project number:** 5R01NS097781-04
- **Recipient organization:** UNIVERSITY OF LOUISVILLE
- **Principal Investigator:** DENA R. HOWLAND
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $578,717
- **Award type:** 5
- **Project period:** 2017-04-01 → 2022-03-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9894867

## Citation

> US National Institutes of Health, RePORTER application 9894867, Altered Motor Function & Force Feedback After Spinal Cord Injury (5R01NS097781-04). Retrieved via AI Analytics 2026-05-22 from https://api.ai-analytics.org/grant/nih/9894867. Licensed CC0.

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