What you're describing is referred to as reactivation. According to the Standard Model of Consolidation, the hippocampus has connections with various areas of sensory cortex. In effect, it too receives the sensory input from the various areas of cortex during an episode. With this information, the hippocampus can replay the neural firing patterns and construct a memory trace even though the sensory stimuli is no longer present.

To your second question - is the firing pattern identical during original encoding and reactivation - I'm not sure there is a definitive answer yet. However, there is good behavioral evidence which suggests it is not always. It has been well-established that memories undergo considerable modification during encoding, storage and retrieval. It's unlikely the memory trace retrieved from storage is identical to the trace originally encoded. If it was, human beings should never make memory errors. However, memory errors are very common.

Yes, the initiating patterns can be different but when recall is complete they will be similar.

Hi Han,

I will try to follow up on what Blaine has explained. There are two points that need to be taken into consideration in what you're reading. The first one is the memory phase you're looking at. As Blaine well said, you're studying what is happening during the consolidation of a given memory, which means the brain is undergoing plasticity changes in order to register a given event and the stimuli associated with that event (the firing patterns you're reading are associated with that. It doesn't mean that during memory recall (a different phase of the memory process), these firing patterns will be happening again as if the firing patter itself represented what the memory means to the brain.

It leads us to the second point, which is the brain region you're looking at: the hippocampus. The hippocampus is heavily involved in the memory consolidation process, specially the spatial components of a given memory. But it is not where the memory is stored. The hippocampus is not the equivalent of a biological Hard Drive (HD). It's more like a hub that coordinate the encoding of new information throughout the whole CNS.

Blaine Tomkins Karl Sipfle Douglas Formolo

Thanks for your answer! Those answers are very useful for a new learner in brain science!

Actually I'm trying to find some memory theory to help me design AI algorithm. So I'm very curious about how our brain encoding our memory and retrieval it without samples replay. So according to your answer, may I understand in this way: when sensory input rereceives, the memory encoding happens and the firing pattern is associate with that memory. In this term, if memory recall happens, same firing patterns will occur. But after this short-term memory is consolidated into long-term memory (for example in complementary learning systems theory), the firing patterns will not be same.