Heterarchic reinstatement of long-term memory: A concept on hippocampal amnesia in rodent memory research

- Hippocampal disruption causes retrograde amnesia for many types of memory.
- Hippocampal disruption spares the ability to acquire many new memories.
- No consensus has emerged on an explanation of these outcomes.
- We present a new concept to explain these findings and generate novel predictions.

Evidence from clinical and animal research highlights the role of the hippocampus in long-term memory (LTM). Decades of experimental work have produced numerous theoretical accounts of the hippocampus in LTM, and each suggests that hippocampal disruption produces amnesia for specific categories of memory. These accounts also imply that hippocampal disruption before or soon after a learning episode should have equivalent amnestic effects. Recent evidence from lesion and inactivation experiments in rodents illustrates that hippocampal disruption after a learning episode causes memory impairment in a wider range of memory tasks than if the same disruption occurs before learning. Although this finding supports that multiple circuits can acquire and retrieve similar information, it also suggests they do not do so independently. In addition, damage after learning produces amnesia for simple elements of a task as well as complex, conjunctive features. Here we develop an explanation for why anterograde and retrograde hippocampal effects differ. This explanation, the heterarchic reinstatement view, also generates novel predictions.