Infant rats can acquire, but not retain contextual associations in object‐in‐context and contextual fear conditioning paradigms

Context learning in postnatal day (PD) 16–18 rats has been taken by Revillo, Cotella, Paglini, and Arias (2015, Physiology & Behavior, 148, 6–21) to challenge the view that the ontogeny of contextual learning is related to the development of the hippocampal system (Rudy, 1993, Behavioral Neuroscience, 107(5), 887–891; Schiffino, Murawski, Rosen, & Stanton, 2011 Neurobiology of Learning and Memory, 95(2), 190–198). Whether context learning is “incidental” or “reinforcement‐driven” may determine the ontogeny and neural systems involved (Rudy, 2009, Learning & Memory (Cold Spring Harbor, N.Y.), 16, 573–585). However, we have shown differential ontogeny of two different forms of incidental context learning, the context pre‐exposure facilitation effect (CPFE; Jablonski, Schiffino, & Stanton, 2012, Developmental Psychobiology, 54(7), 714–722), which emerges between PD 17 and 21; and object‐in‐context recognition (OiC, Ramsaran, Westbrook, & Stanton, 2016, Developmental Psychobiology, 58(7), 883–895; Ramsaran, Sanders, & Stanton, 2016, Behavioural Brain Research, 298, 37–47), which is present on PD17. We investigated whether this task‐dissociation reflects an encoding or a retention deficit, by varying the sample‐to‐testing intervals for both tasks. Experiment 1A found that PD17 rats were able to perform the OiC task after short (5 min) but not long (24 hr) sample‐to‐test intervals. Experiments 1B and 1C found that PD17 rats trained on the CPFE are able to acquire and express context‐shock associations after short but not long retention intervals. These findings suggest that pre‐weanling rats encode contexts but show poor consolidation or retrieval after longer retention intervals.