Mental Scene and Memory Construction and the Hippocampus

A neurocomputational theory of scene and memory construction during memory recall, prospective thinking, and autobiographical memory is described. The theory describes the nature of the representation of scenes using spatial view cells in a continuous attractor network in the medial parahippocampal cortex, and how the location in the scene being represented can be shifted by self-motion eye position update even when the scene is not visible. The theory builds on the evidence for humans for a ventromedial visual cortical scene pathway via the prostriate cortex and ventromedial visual cortical regions to the medial parahippocampal scene (or place) area where scenes are represented. The approach builds on a theory about how visual features in scenes are used along this pathway to build a continuous attractor network representation of scenes in the medial parahippocampal cortex that represents the relative spatial locations of features or landmarks in the scene. The theory shows how episodic memory can be built in an attractor network in hippocampal CA3 that learns associations between the location in a scene ("where"), the object or person at that location in the scene ("what"), and the reward/affective value conveyed to the hippocampus from the orbitofrontal cortex in part via the ventromedial prefrontal cortex and posterior cingulate cortex. The theory of scene construction then shows how backprojections from hippocampal CA1 via the entorhinal cortex to the medial parahippocampal cortex can recall or construct the scene representation in the medial parahippocampal cortex, the parahippocampal scene (or place) area; and how whole memories including visual imagery of objects, rewards, and their locations in scenes can be constructed by iterative neocortical-hippocampal-neocortical processing.