Dynamic extinction and novelty-triggered recovery of visual route memories in 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 bull ants ( Myrmecia) 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, consistent with a gradual 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 this extinction-like process is labile, and the original memories are preserved. Unlike classic paradigms, this decline appears to operate 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 may reflect parallel memory processes in the insect mushroom bodies, where temporal estimates of view exposure could drive this extinction-like decline and novel view detection gates memory recovery.