Asymmetric Walkway: A Novel Behavioral Assay for Studying Asymmetric Locomotion

Summary

Here, we present a protocol to quantify precise stepping in rodents. Cortical and the spinal central pattern generator signals are required for precise foot-placement during obstructed locomotion. We report here the novel constrained walking task that directly examines precise stepping behavior.

Abstract

Behavioral assays are commonly used for the assessment of sensorimotor impairment in the central nervous system (CNS). The most sophisticated methods for quantifying locomotor deficits in rodents is to measure minute disturbances of unconstrained gait overground (e.g., manual BBB score or automated CatWalk). However, cortical inputs are not required for the generation of basic locomotion produced by the spinal central pattern generator (CPG). Thus, unconstrained walking tasks test locomotor deficits due to motor cortical impairment only indirectly. In this study, we propose a novel, precise foot-placement locomotor task that evaluates cortical inputs to the spinal CPG. An instrumented peg-way was used to impose symmetrical and asymmetrical locomotor tasks mimicking lateralized movement deficits. We demonstrate that shifts from equidistant inter-stride lengths of 20% produce changes in the forelimb stance phase characteristics during locomotion with preferred stride length. Furthermore, we propose that the asymmetric walkway allows for measurements of behavioral outcomes produced by cortical control signals. These measures are relevant for the assessment of impairment after cortical damage.

Introduction

Post-stroke morbidity in the surviving population includes gross motor impairments that pose a challenge for quantitative evaluation in both humans post stroke and animal models of neurologic impairment¹. In the clinical setting, these motor impairments are measured using subjective criteria which are more sensitive to severe rather than moderate impairment exhibited by the majority of patients. Similarly, such subjective assessments of post-injury motor behavior in animals are common, e.g., the Basso, Beattie, and Bresnahan (BBB) locomotor scale method^2,3. While these subjective evaluation methods are helping translation between gait re....

Protocol

The following training paradigm employs the analysis of phase adjustments of the average adult Sprague-Dawley rat. Please ensure that the protocol described herein is in accordance with your institutional animal care guidelines. All procedures in this study were performed in accordance with the Institutional Animal Care and Use Committee (IACUC) and Office for Laboratory Animal Welfare (OLAW) at West Virginia University School of Medicine and abides by the National Institutes of Health guidelines for the use of experimental animals.

1. Equipment Setup

1. Construct the asymmetric walkway as an open-top plastic box braced with alumin....

Results

Figure 2 shows the analysis of asymmetry during the locomotor tasks for a single representative subject. The values were calculated for all conditions using Equation 1 and 2 from all subjects individually (Figure 2) and from composite data of 8 female Sprague-Dawley rats (250 - 400 g, Figure 3). Generally, the modulation of the forelimb stance phase was lesser for the side to which the locomotion condition was favored (short ISL), consist.......

Discussion

The rationale for this study was to develop a behavioral task that quantitatively assesses the changes in precise control of asymmetric locomotor behaviors. The existence of the spinal CPG has been functionally demonstrated for some time²⁰, but the anatomical and functional characteristics that describe its mechanism as well as its modulatory inputs from descending or sensory feedback pathways have not been characterized until the past decade^6,21,22. The current consensus is that the intrinsic spina.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
MATLAB® R2013a	MathWorks		Design platform for custom videoa video annotation software
Sony HDR-CX380/B High Definition Handycam	Sony	27-HDRCX330/B	Video acquisition device.
Jif Creamy Peanut Butter - Gluten Free 454 g	J.M. Smucker Company		Food reward stimulus.
Sucrose Tablet - Chocolate 1800 g	TestDiet	1811256	Food reward stimulus.
Manzanita Wood Gnawing Sticks	BioServe	W0016	For presentation of food reward stimulus.