Abstract

 “Both of these receptor types mediate post synaptic transmission in the hippocampus.” https://www.sciencedirect.com/science/article/abs/pii/089662739390308E

It must also be acknowledged that through the ventral tegmental area.  Gaba acts as an inhibitory transmitter by two specific receptor types.  This can affect synapses and synaptic plasticity.  Glutamate works in direct contrast to Gaba and is equally important in its function in the hippocampus (and brain);

(actually,  the metabolic  precursor to Gaba).

The amygdala is also in the mix here with connections to the hippocampus.  The amygdala brings to the table emotional memory recalling and regulation.  Stress hormones such as cortisol and adrenalin can be promoted by the amygdala to make memories more vivid.  The importance of this area of the brain cannot be understated.  However, in later life, both somatostatin and dopamine levels reduce (not in everyone but most) with the aging process. This is where the addiction becomes a problem.  The hippocampus’ activity still wants the same amount of dopamine for each memory and will demand it without compromise.  It is only a matter of time there will be shortfalls of dopamine in the predetermined process.  Even with this happening, the addiction in memory is so high it would rather self-destruct than to give up this once efficient process. 

Another important area is the entorhinol cortex which receives input into the hippocampus from other areas of the brain and in turn sends output from the hippocampus to selected areas.  It is also one of the first sites of tau deposition.

New memories eventually fail to register (not enough dopamine & somatostatin), old memories become irretrievable (the reward levels of dopamine are not high enough to bring back a memory previously registered or encoded above a failing mechanism such as this).  Dopamine & somatostatin are not only a major player in making memories but also crucial for retrieval.  Associated memories can help temporarily to make an Alzheimer’s sufferer bring back a distant memory.  However this process will eventually fail as the illness progresses.

Not everyone gets Alzheimer’s.  Not everyone is an addict.  A general feed of dopamine by the ventral tegmental area/locus coereleus area makes a good memory.  However it does not present as an addiction.  Therefore when dopamine and somatostatin do drop the hippocampus is willing to function with the new circumstances.  Explicit memories can still be formed with this flexibility and also retrieved.

“A recent theory which suggests that a desynchronized neo cortex and a synchronized hippocampus need to interact (in particular the medial prefrontal cortex) to form and recall memories”.  Basically, dopamine is the want for this to also happen.

https://theconversation.com/how-memories-are-formed-and-retrieved-by-the-brain-revealed-in-a-new-study-125361 How memories are formed & retrieved in the brain revealed in a new study-The Conversation

https://www.frontiersin.org/articles/10.3389/fnhum.2021.620342/full Emotion Regulation of Hippocampus Using Real Time…FMRI; Neurofeedback in Healthy Human / Human Neuroscience-Frontiers

https://www.sciencedaily.com/releases/2020/06/200605105359.htm Memory consolidation during REM sleep; Researchers identify neurons responsible for memory consolidation during REM sleep – Science Daily

https://www.sciencedirect.com/science/article/pii/B9780124081390000055 Dopamine & Memory