Decoding the cognitive map: ensemble hippocampal sequences and decision making

•Sequences of spiking are the dominant organization principle of hippocampal activity.•New ensemble techniques allow observation and detection of hippocampal sequences.•Sharp-wave sequences are involved in both consolidation and choosing future behavior.•Theta sequences support online planning to guide behavior in real time.

Tolman proposed that complex animal behavior is mediated by the cognitive map, an integrative learning system that allows animals to reconfigure previous experience in order to compute predictions about the future. The discovery of place cells in the rodent hippocampus immediately suggested a plausible neural mechanism to fulfill the 'map' component of Tolman's theory. Recent work examining hippocampal representations occurring at fast time scales suggests that these sequences might be important for supporting the inferential mental operations associated with the cognitive map function. New findings that hippocampal sequences play an important causal role in mediating adaptive behavior on a moment-by-moment basis suggest specific neural processes that may underlie Tolman's cognitive map framework.