Date on Master's Thesis/Doctoral Dissertation

5-2020

Document Type

Doctoral Dissertation

Degree Name

Ph. D.

Department

Interdisciplinary and Graduate Studies

Degree Program

Interdisciplinary Studies with a specialization in Translational Neuroscience, PhD

Committee Chair

Whittemore, Scott

Committee Co-Chair (if applicable)

Magnuson, David

Committee Member

Brueckner-Collins, Jennifer

Committee Member

Jones, Kathryn

Committee Member

Neimat, Joseph

Committee Member

Mellen, Nicholas

Author's Keywords

spinal cord injury; locomotion; central pattern generator; interneurons; propriospinal neurons

Abstract

The focus of this dissertation is to explore the functional role of two anatomically-defined pathways in the adult rat spinal cord before and after spinal cord injury (SCI). To do this, a TetOn dual virus system was used to selectively and reversibly silence neurons with cell bodies at spinal segment L2 and projections to spinal segment C6 (long ascending propriospinal neurons, LAPNs) and neurons that originate in the C6 spinal segment and terminate at L2 spinal segment (long descending propriospinal neurons, LDPNs). This dissertation is divided into five chapters. Chapter One provides background information regarding spinal cord injury, locomotion, and a brief introduction to propriospinal neurons. Chapter Two details the functional consequences of silencing LAPNs and LDPNs in uninjured animals, with specific regard to sensory context during overground locomotion. Chapter Three describes the consequences of silencing LAPNs following a mild/moderate spinal cord contusion injury. Spinal cord injury (SCI) fundamentally affects the ability to maintain patterned weight-supported stepping. Chapter Four focuses on the functional outcomes of silencing the reciprocal descending inter-enlargement pathway, LDPNs, after mild/moderate spinal cord contusion injury. Finally, Chapter Five compares the differential roles of LAPNs and LDPNs in left-right coordination prior to injury, especially in a sensory context-dependent manner. A section of this chapter is devoted to a recap of injured data for both LAPN and LDPN silencing post-injury and attempts to place this work in context with other studies whose focus is on propriospinal pathways after SCI.

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