Novel Speed-Controlled Automated Ladder Walking Device Reveals Walking Speed as a Critical Determinant of Skilled Locomotion after a Spinal Cord Injury in Adult Rats

Abstract

The horizontal ladder task is an established method to assess skilled locomotor recovery after neurological dysfunction. Walking speed is often used as a standardized measure in locomotor assessment of overground walking in human and pre-clinical studies, but the assessment of walking speed is typically ignored during skilled locomotor tasks. Ample empirical evidence indicates that walking speeds on the horizontal ladder are largely non-uniform after central nervous system trauma, suggesting that it could pose a potential source of variability in assessing motor deficits. Here, we investigate whether walking speed influences the assessment of motor recovery during skilled walking after a spinal cord injury (SCI). We hypothesized that if rats walk at imposed walking speeds, motor deficits and recovery after an SCI will be more reliably assessed than when not controlling walking speeds. To address this, we developed a novel speed-controlled Automated Device for the Assessment and Training of Skilled locomotion (ADATS) as a surrogate device to the horizontal ladder. The ADATS allows testing at user-defined speeds, thereby forcing the rats to step consistently. Our results demonstrate that: 1) the ability to walk (or not) at one or multiple speeds on the ADATS serves as a gross measure of motor dysfunction/recovery after a spinal cord injury and 2) skilled motor deficits are more readily detected at lower than higher walking speeds. We conclude that walking speed is an important factor in the analyses of skilled locomotion and testing at multiple speeds is useful in accurately measuring recovery after neurotrauma in rats.