What is the role of spatial processing in the decline of episodic memory in Alzheimer's disease? The "mental frame syncing" hypothesis.

The current theories on episodic memory suggest a crucial role of spatial processing for an effective retrieval. For a successful episodic recall, the long-term allocentric scene has to be translated into an egocentric scene. Here, we argue that a crucial role for an episodic retrieval is played by a "mental frame syncing" between two kinds of allocentric representations. This neurocognitive process allows an effective retrieval of our past experiences by synchronizing the allocentric view-point independent representation with the allocentric view-point dependent representation. If the "mental frame syncing" stops, even momentarily, it is difficult to reconstruct a coherent spatial scaffold upon which to effectively retrieve our previous events within an egocentric perspective. This is what apparently happens in Alzheimer's disease: a break in the "mental frame syncing" between these two kinds of allocentric representations, underpinned by damage to the hippocampus, may contribute significantly to the early deficit in episodic memory.