What, physiologically speaking, is a memory?

I know it is a stupid question with a complicated answer, but in relatively simple terms, how is a memory encoded into the brain? Is it stored on particular neurons, or on a sequence of neurons, or…?

Any recs for readings on the physiology of consciousness?

If you can get any books be Eric Kandel, he is (IMO) the dude when it comes to memory.
Priciples Of Neural Science
Memory…Mind to Molecules
If you read the first, you may be able to follow the second.

And if you want just a high level overview of the physiology of memory, plus some significant history on the development of our current understanding of memory, Kandel’s memoirs, In Search of Memory: The Emergence of a New Science of Mind is also a good read. He goes into a fair amount of detail about his ground-breaking work with sea slug Aplysia despite advice to the contrary from his mentors, and from there to more complex neurology. This is interspaced with anecdotes about fleeing the Anschluss and how he got into medicine, psychiatry, and neruological research, which is actually pretty fascinating. Kandel is, as vetbridge says, the leading authority on the physiology of memory in mammals, and the first reference is the definitive text on the subject. (I haven’t read the second so I can’t comment on it.)

The short but manifestly incomplete answer to your question is that short term memory is the result of enhanced sensitization of a neural junction via repeated or intense stimulation and the resultant concentration of a “messenger molecule” (cyclic adenosine monophosphate, or cAMP) that makes repeated stimulation easier. Long term memory is the result of protein synthesis of conduction pathways due to repeated stimulation. The process involved in this is far more complicated and still not entirely well-understood (though the research of Kandel and his associates has advanced the field of knowledge by leaps and bounds and contributed to pharmacological therapies to treat physiological memory disorders) and beyond the scope of an easy response, but basically, the brain builds more and stronger connections which become preferred.

This all deals with individual processes of memory; the stimulation of a single ganglion. How this all relates to high level conceptual memory like an image or a quotation, and how this is intergrated into the mass of processes that make up the gestalt of consicousness and cognition is not at all well-understood except on a very simple causation-action model (which clearly doesn’t account for complex problem solving or ‘free will’, whatever that is) and Kandel would be the first to agree that the overall phenomena of consciousness is beyond our ability to explain in detail at the present state of neurology, much to his lament.

But read Kandel; he explains it far better than I could here, or indeed, anywhere.


Actually, Stranger does a good job explaining some of what is known about a complex subject.

Amusing anecdote:
I worked in a lab run by a contemporary of Kandels. One day Eric called the lab with a question regarding a soon to be released paper that I had coauthored. I wrote, “Eric Kandel 222-555-1212” on the dry-erase board so that my boss could return the call when he arrived.

Anyway, my boss asked me not to erase the board. Bastard was so vain, he wanted the world to see who had called him! :rolleyes:

ETA: I checked Stranger On A Train’s location. No, he is not my old boss.

Stranger certainly put it down as well as I could have. If you don’t want to take the time to read a book, here is a short article on the subject. I was suprised to find I did not need to log in to get it, but perhaps somehow the host knows me.

Anyway this will wrap things up nicely, including how the brain sorts memories and reorganizes them for recall.