Noncanonical circuits, states, and computations of the hippocampus

Traditional views of hippocampal function are largely based on the canonical flow of information from the entorhinal cortex through the trisynaptic loop—comprising the dentate gyrus and cornu ammonis regions CA3 and CA1—and back to cortex, where the hippocampus plays an important role in transforming relevant information into a usable storage system. This classic circuit has inspired current thinking on hippocampal functions related to learning, memory, and spatial navigation, but the potential functional contributions of other hippocampal areas, such as CA2, the fasciola cinereum, and the indusium griseum, and their integration of a major hypothalamic input, have been overlooked. These understudied circuits and nontraditional network dynamics such as dentate spikes have recently begun to yield fresh insights into unconventional circuit computations that extend the repertoire of hippocampal function beyond current models.