“Only AmHipp” (medial bank of the anterior hippocampus)
Posterior only gets used for ELABORATION, which is very specific and probably visual.
Episodic memory and imagination
FMRI studies of episodic (autobiographical) memory, which require participants to vividly recall specific events from their past, generally find that a ‘core network’ of brain regions — including anterior hippocampus — is engaged
Activation within the hippocampus may be limited to amHipp.
For example, when subjects were cued to imagine static atemporal scenes based on short descriptions, amHipp was the only part of the hippocampus to be significantly engaged, relative to a control condition in which participants imagined isolated static objects.
Specific increases in amHipp activity were found in another study in which subjects constructed and elaborated upon past events and imagined future events.
When participants recalled episodic memories and imagined fictitious events set in the past or future (based on recombined elements from episodic memories) the amHipp was again the only part of the hippocampus significantly engaged for imagination and was part of a larger region activated during both imagination and recall whereas activation of posterior hippocampus was found specifically for vividly recalling real memories.
Only amHipp was found to respond more strongly to imagining specific past or future events rather than general events, whereas the anterior lateral hippocampus distinguished past from future episodes.
Autobiographical memory retrieval was also found to engage only amHipp (Figure e) although other subregions of the hippocampus were responsive to whether retrieval was cued using a direct association with the cue or a strategy of searching through memories.
A subsequent study sought to distinguish the initial construction stage of autobiographical memory recall from elaboration , and within the hippocampus found solely amHipp engagement for construction.
Posterior hippocampus was engaged for elaboration, which connectivity analyses showed was also linked to areas processing visual stimuli.
These studies suggest that despite different research questions, tasks and some points of divergence – including the extent of differences between recalling the past and imagining the future and the relationship between imagination, novelty and encoding – one common feature across studies was the engagement of amHipp, in addition to regions of the wider core network , , , .