A novel device for precise training and perturbing of motor cortically driven forelimb behaviors in the rat

Abstract

Compared to humans and non-human primates, the rat is a promising model for studying the motor cortex during structured behavioral tasks due to its low cost and rapid trainability. However, options for behavioral tools for investigating motor cortically driven forelimb behaviors are limited. Here, we developed a one-dimensional rotation manipulandum for rat forelimb supination training that has low-latency, high-resolution detection of holding and turning. Additionally, we characterized the system to accurately produce a range of torques that could be used to dynamically perturb rodent forelimb rotation behavior with high precision. Following characterization, we validated the behavioral device using two behavioral paradigms, a static holding task and a knob turning task with virtual stiffness. Rats trained on the static holding task saw significant increases in their holding durations, while those trained on the knob turning task had significantly decreased peak turning angles as motor torque was increased. This end-to-end characterization showed our device to be effective at training and perturbing multiple potentially motor cortically driven behaviors. Ultimately, we hope to use this tool to uncover evidence of a dynamical system in rat motor cortex, like those already discovered in humans and monkeys.