Forced Movements Facilitate Reversal Learning in Rats: Findings from a Rat Robotic Rehabilitation Model

To evaluate the effectiveness of robotic rehabilitation alone, we developed a robotic rehabilitation model for rats and investigated the effects of inducing forced response-like movements on learning a choice reaction time task. The rats, while in a standing position, initially press two levers with their forepaws. An air-puff stimulation (go-signal: GS) is then applied to either their left or right forepaw. The rats respond by releasing the lever on the correct-response side (correct-RS). If the rats respond incorrectly, a lever-release motion is forcibly induced in the next repeated trial. Combining the lever activation side (correct-RS or incorrect-RS) and its timing (200 ms after GS or just before reaction time (RT)), we formed four experimental groups. The rats with a forepaw sensorimotor cerebral lesion were trained in serial reversal learning of the task, and their performance was compared using the error rate (ER) and RT. The group with incorrect-RS lever activation after GS (iRSaftGS) and the group with correct-RS lever activation before RT (cRSbfrRT) had lower ERs and RTs than the other groups. In addition, both groups showed large improvement in ER at high ER levels but only the iRSaftGS group's improvement continued at lower ER levels. We conclude that the cRSbfrRT group facilitates only the extinction process and that the iRSaftGS group, which stretches agonistic muscles required for correct motion, is effective in both extinction and acquisition processes. Our findings provide an opportunity to reconsider the strategies for robotic rehabilitation and training.