We designed a behavioral task where rats learn to associate two temporally distinct but close-in-time events by means of incidental one-trial learning. The task takes advantage of two competing motivations - to avoid light places and to avoid painful stimuli (foot shock) predicted by an acoustic signal. Motivation to avoid a bright light is constant throughout the experiment and is manifested by rats preferring a dark compartment in a light/dark shuttle box. Motivation to stay in the dark is overridden (1) during the training session: when foot-shock (US) (preceded by the acoustic stimulus (CS)) is presented; and (2) during the testing session: when CS, that predicts US, is presented. The latter case occurs when rats successfully form an association between CS and US in the training session and the rat escapes into the light compartment ('responders'). The rats that do not escape ('non-responders' appear to lack this memory as even non-specific fear response (freezing) was absent.

Generally, >50% of rats escape into the lit compartments following CS on the testing day. Importantly, rats do not show a contextual association measured by freezing behavior and preference for a light compartment on the testing day. Moreover, we observed that several putative details in the setup affect the probability of the successful formation of a one-trial trace association. Compared to similar tasks, the OTTER task tests incidental learning with no requirement for pre-training. Moreover, the memory formed in the OTTER task consists of two events that do not overlap in time: a characteristic of many episodic memories. The OTTER task presents high-throughput means to study neuronal substrates of incidental temporal binding.

Radostova_OTTER_manuscript_data.csv shows the habituation behavior of rats in the OTTER task. This file also identifies ‘responders’ and ‘non-responders’. Radostova_OTTER_manuscript_data_freezing.csv shows the freezing for 1 minute following conditioned stimulus presentation during the recall session, and shows no difference in freezing between 'responders' and 'non-responders'.