In partial fulfillment of the requirements for the degree of

Doctor of Philosophy in Applied Physiology

In the

School of Biological Sciences

Adam De Boef

Will defend his dissertation

Mechanisms and Control of Widespread Spinally Mediated Inhibition

7th April 2023

1:30pm

In person: Applied Physiology Building, Room 1253, 555 14th St NW, Atlanta, Ga. 30318

https://gatech.zoom.us/j/3879995674 

 Thesis Advisor:

Richard Nichols, Ph.D.

School of Biological Sciences

Georgia Institute of Technology

Committee Members:

Timothy Cope, Ph.D.

School of Biological Sciences

Georgia Institute of Technology

Boris Prilutsky, Ph.D.

School of Biological Sciences

Georgia Institute of Technology

Dena Howland, Ph.D.

Dept. of Neurological Surgery and

Anatomical Sciences and Neurobiology

University of Louisville

Mark Lyle, Ph.D.

Division of Physical Therapy

 Emory University

ABSTRACT:

Proprioceptive feedback plays a crucial role in motor control.  Proprioceptive feedback allows muscles to interact with one another, through excitatory and inhibitory pathways. Historically, there is a debate about the extent to which each proprioceptor contributes to intermuscular interactions.   Furthermore, the regulation of this inhibitory network is poorly understood. Previous work from our lab suggested they are mediated by the force sensitive (Ib) pathways alone. However, synaptic connections within the spinal cord suggest the connections should be mediated by a combined length and force contribution.

Previous work from our lab demonstrates that incomplete spinal cord injuries (iSCI) disrupt inhibitory network between muscles. Utilizing three different iSCI models, the proprioceptive sources of intermuscular inhibition, and the descending control of the corresponding interneuronal network, were investigated. This project provides evidence that the group II afferents contribute to intermuscular inhibition and become over expressed after iSCI.  These results provide new insights into the physiological function of force and length receptors projecting to the spinal cord. In addition, the results indicate that the medullary reticulospinal pathway regulates the structure of inhibition across the feline hindlimb, adding to the understanding of the role of this pathway in the regulation of posture and limb mechanics.