Online extinction and novelty-triggered recovery of life-long visual memories in navigating ants

Abstract

Insects exhibit flexible memory processes, yet current models often confine these modulations to discrete, reinforced events. During navigation, animals can learn to associate locations with resources or aversive events. However, such events occur sporadically within an otherwise continuous behavioral process involving latent learning. This raises a fundamental question for insect cognition: can insects continuously update visual memories during navigation? We show that navigating ants (Myrmecia midas) dynamically revalue visual memories en-route, even in the absence of any motivational change or external reinforcement. Using a trackball system that prevented visual progress, we found that nest-view attraction declined over time, reflecting a gradual, online extinction of these otherwise life-long attractive visual memories. These memory updates were view-specific, independent of path integrator state, and persisted after 24-hours, indicating the involvement of long-term memory processes. However, brief exposure to a novel visual scene was sufficient to partially restore nest-views attraction, showing that extinction is labile, and the original memories are preserved. Unlike classic paradigms, visual memory extinction operates here as a continuous, time-dependent process without reward-omission or prediction error; whereas memory reinstatement is triggered by discrete visual changes. We propose that these dynamics are mediated by opponent-processes in the insect mushroom bodies, where temporal estimates of view exposure drive extinction and novel view detection gates memory recovery.