Determinants of object-in-context and object-place-context recognition in the developing rat.

Since the seminal report on novel object recognition in the rat (Ennaceur & Delacour, 1988), novelty recognition paradigms have become increasingly prevalent in learning and memory research. Novelty recognition tasks do not require extensive training or complex behaviors, and thus are especially suitable for studying the ontogeny of various forms of memory (e.g., object, spatial, and contextual memory). However, relatively little is known about the determinants of recognition memory during development. The present study extends our recent research on the development of recognition memory by further characterizing the ontogeny of contextual recognition (Ramsaran, Westbrook, & Stanton, 2016). We report that long-term retention of object-in-context (OiC) memory emerges during early development in the rat (Experiment 1), and that performance of object-place-context (OPC), a spatial variant of the OiC task, also displays protracted development until early adolescence (Experiment 2). In addition, we examined the role of NMDA receptors (NMDARs) in contextual recognition and found that OiC memory is not dependent on NMDAR-mediated plasticity whereas performance of spatial task variants including the distal cue OiC (Ramsaran et al., 2016) and OPC tasks are NMDAR-dependent (Experiments 3 and 4). The ontogeny of contextual recognition is influenced by memory retention and spatial processing demands, which may also determine the neurobiological mechanisms supporting task performance.