Multi-level analyses of associative recognition memory: the whole is greater than the sum of its parts

Associative recognition memory depends on the integration of information concerning an item and the spatio-temporal context in which it was encountered. Such an integration depends on dynamic interactions across a brain-wide memory network. Here we discuss evidence from multiple levels of analysis, behavioural, cellular and synaptic which demonstrating the existence of multiple overlapping, subnetworks embedded within these large-scale networks. Recent advances have revealed that of these subnetworks, a distinct hippocampal-prefrontal networks are engaged by different representations (object-spatial or object temporal). Other subnetworks are recruited by distinct processing demands, such as encoding and retrieval which are supported by distinct cellular and synaptic processes. One challenge to multi-level investigations of memory continues to be that conclusions are drawn from correlations of effects rather than from direct evidence of causation.