I read that humans have 2 memory systems.

One is fight or flight memory located in amygdala. Another is episodic memory located in hippocamus.

Then I've heard that there is another memory system. Semantic memory located on the temporal lobe.

So, how many memory systems do we have?

If I can derive most math formula on top of my head but keep forgetting where I put my glasses, is something wrong in my hippocampus?


Okay, how many memory do we have?

Like many things in neuroscience & cognitive science, it depends on how you categorize it, it is also an evolving field and you might be surprised to know that the number of memory systems is closer to 10-12, although the number might go up or down in the future.

In general there are 2 ways of dividing memory: by time range ( Long term and short term) and by intentional recollection, each one further subdivides and overlaps at some points.

One is fight or flight memory located in amygdala.

The Amygdala is a complex mass of gray matter that plays an important role in emotions, it both integrates and has a role in associative learning in between stimuli and experiences/feelings among other functions, so in a way it is involved in memory, ( emotional memory).

The fight or flight response on the other hand is a whole other complex subsystem of our bodies mainly involving the visceral motor system (the sympathetic division)

Another is episodic memory located in hippocamus

Episodic memory is one of the subdivisions of memory, mainly dealing with events as opposed to facts ( that would be semantic)

The hippocampus is a crucial component to memory, but is part of a bigger system mainly involved with transfering and facilitiating the creation of short term memories to long term memories.

If I can derive most math formula on top of my head but keep forgetting where I put my glasses, is something wrong in my hippocampus?

Most likely not, as this very brief and incomplete review hopefully shows you, there are a number of different systems at play for what we normally bunch up into the word memory, there are also different types of memories.

Deriving a math formula on the top of you head involves another type of memory, working memory, along with the phonological loop if you think in words about your equations ( these 2 are sort of buffers) , and long term memories across your neocortex with a number of connections and interconnections, in other words your whole brain lights up.

Forgetting your glasses on the other hand is usually a problem of not encoding the initial percept in the first place ( i.e. to increase the odds of you finding your glasses again, you need to consciously aknowledge where you are leaving them in the first place rather than just dropping them).

Additionally, what you do in between leaving your glasses and trying to recover them also influences how much you remember them.

As mentioned memory is a complex and deep subject, as way of sources here are a few books I consulted:

- Cognitive Neuroscience (Third edition) - Neuroscience (Third edition)
- In search of memory - The seven sins of memory

  • $\begingroup$ Thank you for the answer. First hand references to scientific articles are preferred over wikipedia links, however. If you have some that you could share, it would greatly improve the quality of your answer. A plus one, nonetheless ;) $\endgroup$ – Robin Kramer Nov 27 '16 at 20:17
  • $\begingroup$ @RobinKramer: Thanks, the question I think identifies certain areas/functions incorrectly, so there was a lot of jumping from book section to book section and overviews, hence no direct reference; for instance the learning and memory section on cognitive science has some 20 - 30 scientific papers I think to come up with the 10-12 number of memory systems estimate, so a lot of simplifications need to be made, i.e. there is sometimes no scientific article that can directly answer some CS introductory questions, but I think it is important to answer them. $\endgroup$ – Keno Nov 27 '16 at 22:19

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