Experience, memory, and the places they meet.

Studies of learning and memory have made significant advances in characterizing the mechanisms of single memories, formed when surprising and unpredictable events trigger synaptic modifications in response to tightly timed coincidental cues. Yet outside the laboratory setting, few natural experiences are wholly unique, and much of our behavior is shaped progressively through the interactions of perceived experiences, recently formed memories and distant acquired knowledge. Despite the necessity of these memory dynamics, relatively little is known about how previously established associations are accessed, updated, and applied to inform new learning at the appropriate moments in time. Such questions have historically been technically challenging to address because they require prolonged access to circuits linked to past episodes of learning; however, new techniques for function-and activity-based circuit mapping, developed and refined over several decades, have introduced novel opportunities to investigate both broad systems-level functions and detailed circuit mechanisms in complex neocortical systems. This review will focus particularly on insights from studies of the retrosplenial cortex, a large and heavily interconnected region of neocortex that has recently emerged as a candidate node for largescale information exchange over functionally diverse anatomical domains.