Episodic Memory: How we Learn and Remember

12th May 2014

“No sooner had the warm liquid, and the crumbs with it, touched my palate, a shudder ran through my whole body, and I stopped, intent upon the extraordinary changes that were taking place. An exquisite pleasure had invaded my senses, but individual, detached, with no suggestion of its origin. And at once the vicissitudes of life had become indifferent to me, its disasters innocuous, its brevity illusory–this new sensation having had on me the effect which love has of filling me with a precious essence; or rather this essence was not in me, it was myself. I had ceased now to feel mediocre, accidental, mortal. Whence could it have come to me, this all-powerful joy? I was conscious that it was connected with the taste of tea and cake, but that it infinitely transcended those savours, could not, indeed, be of the same nature as theirs. Whence did it come? What did it signify? How could I seize upon and define it? … And suddenly the memory returns. The taste was that of the little crumb of madeleine which on Sunday mornings at Combray (because on those mornings I did not go out before church-time), when I went to say good day to her in her bedroom, my aunt Léonie used to give me, dipping it first in her own cup of real or of lime-flower tea.” Marcel Proust, Remembrance of Things Past

Episodic memory is a complex neurocognitive system, involving both the mind and the brain. It allows us to remember past autobiographical events, prior experiences – memories. Something as miniscule as a smell, sound, word or touch acts as a recovery key, triggering a complex process, allowing one’s mind to travel into the past.

Memory’s cognitive purpose is clear, we are able to travel back in time for emotional growth, comfort and learning. When we have a problem, we can travel back into our past and playback and re-use something that we have learned for present or future applications. Or similarly to Marcel Proust, having the taste of the little crumb of madeleine with tea, transporting him right back to his aunt Léonie’s bedroom in Combray when he was still a little boy. Remembering fond events and people can bring us a rush of happiness and it is through these re-liveable experiences that we can create belief systems, hypothesise about the future and document our lives.

Being able to remember past events requires a mixture of information, such as: smells, sounds, shapes, colours, textures, words, facts among many others. With this information in place the brain is creating a recollection that is as vivid as possible, allowing it to trigger strong emotional reactions.

Even though there are several memory types, there are two overarching ones, long and short term memory.

The episodic memories hallmark is the binding together of the various features of a stimulus or events into an integrated memory presentation. Every little piece of the mixture of information has to be processes by a different neural network in the brain, all coming together to create a memory representation.

The hippocampus, a major component of the brain plays an integral role in the consolidation of information from short and long term memory. It is the hippocampus that gives memories a specific location, helps encode objects and can also act as memory storage, similar to the perirhinal cortex, which doubles up some of these functions. That we remember emotional events better than neural events is due to the amygdalas function, which processes emotional reactions of memories.

There are many more systems that influence how the brain encodes, consolidates and retrieves when it comes to episodic memory, especially neurotransmitters (endogenous chemicals), have been of high interest to scientists of late, as they correlate to cognitive tasks.

There are however ways that we can influence our memories through our mental processes and cognitive behaviours. Reasoning for example has a great impact on the brain. By repetitive and deliberate rehearsing we can impact and determine what information needs to be stored. By paying attention, a memorys encoding can be strengthened, making sure that access to that memory will be easier if needed in the future.

In conclusion, we can see that the episodic memory system is vast, covering various brain systems and cognitive behaviours among many other. However it is one of the most inspiring mechanisms that has evolved to give us an opportunity to not just experience life in the moment, but also to recount all those which shape who we are. It is as if the brain knows how fleeting life events can be so it has evolved a mechanism to hold onto those moments and giving us the chance to relive them.