Darting during platform-mediated avoidance in male and female rats is spatially organized between reward and safety locations

The platform-mediated active avoidance (PMA) task has been used as a rodent model of decision-based active avoidance in which rats learn to avoid a tone-signaled shock. Prior studies utilizing the PMA task have primarily investigated avoidance, freezing, and food-seeking behaviors, but few studies have thoroughly assessed darting behavior, a more recently identified measure of fear that has been largely explored in conditional fear paradigms. Here, we investigated the properties of darting that occur during the PMA task, in which rats either acquired the PMA task alone or with a social partner. We found that rats undergoing solitary PMA produced significantly more darting bouts, whereas rats undergoing social partner PMA produced darts that were faster and shorter in duration. We also found that darting in solitary PMA was predominantly concentrated at the platform, whereas darting in social partner PMA occurred more often outside of the platform and lever zones. Analysis of darting trajectories, which included movements surrounding each darting bout, revealed that darting was embedded in a broader spatially-organized movement between the platform and lever zones, especially during solitary PMA, and this pattern increased across training days. These findings suggest that darting between the platform (safety) and lever (reward) zones reflects transitions between defensive and reward-seeking behaviors, a pattern that strengthens across training and is modulated by social partner condition.