Evolution of declarative memory

The present review considers research on the hippocampus and related areas from humans and experimental animals and makes three main points. First, many of the anatomical details of the hippocampus and adjacent cortical areas in the parahippocampal region are conserved across mammals. Second, the functional role of these areas in declarative memory is also conserved across species. Third, an evolutionary approach will be key to understanding exactly how the local circuitry of the hippocampus and parahippocampal region supports declarative memory. To highlight the utility of this approach, a schematic model is described in which separate streams of spatial and nonspatial information converge on the hippocampus. By this view, a fundamental function of the mammalian hippocampus is to combine incoming information about spatial context from the postrhinal (parahippocampal in primates) cortex and medial entorhinal area with incoming information about nonspatial items from the perirhinal cortex and lateral entorhinal area. The underlying neurobiological computations that arise from local circuitry enable item-in-context memory and are proposed to be fundamental to many examples of declarative memory, including episodic memory in humans and spatial memory in experimental animals.