Differences in neuroplasticity after spinal cord injury in varying animal models and humans

Abstract

Rats have been the primary model to study the process and underlying mechanisms of recovery after spinal cord injury. Two weeks after a severe spinal cord contusion, rats can regain weight-bearing abilities without therapeutic interventions, as assessed by the Basso, Beattie and Bresnahan locomotor scale. However, many human patients suffer from permanent loss of motor function following spinal cord injury. While rats are the most understood animal model, major differences in sensorimotor pathways between quadrupeds and bipeds need to be considered. Understanding the major differences between the sensorimotor pathways of rats, non-human primates, and humans is a start to improving targets for treatments of human spinal cord injury. This review will discuss the neuroplasticity of the brain and spinal cord after spinal cord injury in rats, non-human primates, and humans. A brief overview of emerging interventions to induce plasticity in humans with spinal cord injury will also be discussed.

Disconnected Body Representation: Neuroplasticity Following Spinal Cord Injury

“…Functional cortical plasticity observed after deafferentation is likely to be a result of the reorganization of pathways originating from residual peripheral nerves and extending upward via the spinal cord, brainstem, and thalamus [38]. This notion suggests that the major changes in cortical organization that presumably reflect the adaptation of cortical maps to altered spinothalamic and spinocerebellar input occur due to the collateral sprouting of damaged or spared pathways, which form new neuronal tracts [40].…”

“…The effects of a SCI can present great variability, from slight reduced sensory and motor activity in an incomplete lesion to the abolished sensory and motor and interoceptive signals in a complete lesion, suggesting a degree of cortical reorganization of body which is highly variable [40]. Recent advances by resting state functional magnetic resonance imaging (MRI) indicate that the neural connectivity after acute and chronic SCI appears modified by indicating that reorganization may occur not only in the brain but also in the spinal cord [41,42].…”

Effects of Repetitive Transcranial Magnetic Stimulation (rTMS) and Treadmill Training on Recovery of Motor Function in a Rat Model of Partial Spinal Cord Injury

“…Additionally, there are anatomical differences between rats and humans. The characteristics of pathophysiological changes and spontaneous function recovery are also different after SCI [ 31 ], so further evaluation may be needed to determine its possible clinical effects.…”

“…The training method was modified treadmill training (TT) to produce a standardized and consistent plantar stepping pattern because the pattern of plantar stepping helps activate motor function [ 30 ]. We conducted an animal experiment based on a rat model of partial SCI because rats have been identified to be the primary model to study the underlying mechanisms of function recovery after SCI [ 31 ]. We evaluated motor function by using the Basso, Beattie, and Bresnahan locomotor scale scores and the grid walking test.…”

Effects of Cyclosporin-A, Minocycline, and Tacrolimus (FK506) on Enhanced Behavioral and Biochemical Recovery from Spinal Cord Injury in Rats

“…Much of these therapeutic studies have been reported from animal models, and it needs to be understood that a successful clinical trial in humans can only be initiated based on previously available preclinical data reported from animal model studies that closely mimic the losses as in human SCI functions [11]. Although rats are the animal model of choice for SCI studies, the major anatomical differences in axonal tracts and sensory motor pathways between quadrupeds and bipeds need to be taken into careful account to improve the targets of human SCI treatments [12].…”