The Neuroscience of Memory Formation.steemCreated with Sketch.

in #health5 years ago (edited)

For much of the 20th century it was believed that our brain’s neuroplasticity ended after a critical period of early development. It was thought that once we reached adulthood, our brains settled into a stable and immutable state.  Fortunately for us all, we have found this to be false. 

Anytime you learn something new, whether it be from reading a book, playing an instrument, learning to type, having a stimulating conversation etc., your brain is undergoing neuroplastic changes.  These changes involve the development of new synaptic connections, increased/decreased strength of existing connections, new axonal growth, receptor regulation, ion channel modification and much more. In some regions of the brain, neurogenesis (creation of new neurons) continues to occur throughout life.  One of these regions is the hippocampus, where much of the memory acquisition, consolidation, and retrieval processes occur.

We experience the world as a stream of consciousness - a consciousness which corresponds to particular patterns of neuronal activation in our brains. (Or is that neuronal activation depending on your view of the mind-body problem :D) A critical property of this activation is that it has a lasting effect on the neurons involved, making them more likely to activate in that pattern in the future. If you activate the same pattern, you have the same conscious experience - memories. This general idea of how memory functions was first postulated by Donald Hebb, and is eponymously named Hebbian Theory.

Neuronal pattern reinforcement as a mechanism of memory formation depends on many factors, saliency of experience and the number of times that experience occurs being major contributors. In order for a particular memory to be stored for later retrieval, there must be a mechanism by which very precise networks of neurons can be called upon to fire in the same pattern as they did during the original experience. In essence, this strengthening of very particular neuronal activation patterns is what our memories actually are. So memories aren’t really stored in neurons, but in the pattern of connections between them.

Memories are postulated to be stored in the pattern of connections between neurons.

The principal way in which neurons communicate with one another occurs at sites called synapses -junctions between two neurons with a very small gap through which neurotransmitters move from one neuron to the next. The ability of these synaptic connections to adapt in response to increasing or decreasing stimulation - experience - is called synaptic plasticity. Imagine a complex electrical circuit with many possible pathways between the voltage source and ground. You could modify these pathways with resistors and capacitors in order to produce current along a very particular path of your selection. It is in a similar, though much more complex way that the paths of neuronal firing are “selected” through the modification of their synaptic connections. 

The strength of connectivity between any two neurons in this engrammatic neuronal pattern can and is modified in a number of ways. These include a change in the number of synapses as well as the strengthening/weakening of individual synapses. Together, this is referred to as Long-Term Potentiation. 

Long-Term Potentiation (LTP) can last a few minutes, or many years. Alteration of gene expression is required for long lasting effects. LTP depends on the strength of initial activation and its subsequent maintenance. If you continually activate the same synapses, as happens during repetition and recollection, we strengthen those connections and even create new synapses.

The mechanisms underlying LTP are vast and complex. I will try to give a clear and concise overview of how it works...

The primary excitatory neurotransmitter in the central nervous system is glutamate. So, this is the molecule that’s traveling across 90% of those synapses in our brain. Glutamate is released by the axon terminal of one neuron, and activates the receptors of the post-synaptic neuron. For simplicity, we’ll say glutamate acts on two receptor types. We’ll call them AMPA and NMDA receptors, as that’s what they’re called :D, and we’ll say that AMPA are responsible for “normal” neurotransmission and NMDA are responsible for LTP, though that’s not exactly the case.

Initially, NMDA receptors are blocked by magnesium, and only AMPA receptors are activated by glutamate. However, if the AMPA receptors are activated long enough, or with enough intensity, the magnesium block will be forced out and the NMDA receptors will become active. This initiates a large chain of events which activate a variety of downstream LTP pathways. One of these is the recruitment of more AMPA receptors. Now the next time this synapse is activated, the connection will be stronger due to the increased receptors available to respond to glutamate.

It is in this way (and through a related mechanism - Long-Term Depression), that the connections between neurons and thus the pattern of activation as a whole is modulated and controlled by the experiences we have. Much like the electrical circuit analogy, precise current pathways can be achieved.

This is also why habits are hard to break and addictions difficult to overcome. The more certain neuronal pathways are repeatedly activated, the stronger they become. Fortunately as we learn more about how memories are stored, retrieved, reinforced, and extinguished, we are able to find ways to “hijack” these mechanisms for our own good. The work that I do in particular is supporting this foundation of knowledge in order to better extinguish harmful memories such as those involved in Post-Traumatic Stress Disorder.

As this information is not pulled directly from sources, but from my knowledge/experience developed during a decade in the Neuroscience field, I will not be listing specific references. However, I have provided link throughout the article to relevant information if you would like to learn more about those particular topics. And of course feel free to ask any questions or provide critiques below!
Photo Credit: Richard P J Lambert on Flickr under Attribution 2.0 Generic (CC BY 2.0) license.

- @foundation -

"Education isn't something you can finish."

-Isaac Asimov

I was really pleased to find this article which I will read more carefully later. The development of neuroscience has changed so much in my initial field of hypnotherapy (particularly with regard to the myths around using hypnosis for memory recovery). I am also just starting a masters degree in psychology and am interested in how the current research can inform personal development approaches such as mindfulness. My only caveat would be that the research in general seems to be carried out from a 'mind is an emergent phenomenon of brain' presupposition which, for me doesn't fly.

I look forward to reading more of your work.

Yes, the progression of neuroscience/psychology is very exciting! I too am interested in mindfulness, which of course doesn't require a scientific understanding of the brain to experience. Neuroscience in many ways runs in parallel with the "a-scientific" approaches to discovering the mind, with lots of space for the two approaches to positively influence each other. I don't believe there is a definitive answer on the mind-body problem or whether 'mind is an emergent phenomenon of brain,' but I'm interested to hear what your views are there.

I haven't thought through what I think, so thank you for the opportunity to start doing that. I think it starts with the idea of a 'paradigm' and the concept that a new paradigm must both explain what is already known and be able to explain some of what isn't known.

So looking at a model that incorporates spiritual techniques and maps (such as Buddhist based mindfulness, and my current interest, the so called Three Principles Approach) and the scientific research so that our understanding of 'consciousness' is enriched in a way that actually makes a difference to the way we experience life and so live.

It's a beginning!

I think having a balanced perspective is good. The scientific process can and has revealed much about our brains, but not yet a whole lot on our consciousness. I don't believe consciousness is beyond the purview of science, but we aren't there yet. Intuitive, self-contemplative methods of approaching an understanding of our mind are certainly very useful for our well being. Mindfulness can provide real benefits to those who practice. I haven't heard of the Three Principles Approach, so thank you for sharing!

Holistically, the more you focus on something, ponder on something or give it energy of thought, the more it grows, and becomes a part of your reality.
Ideas are like infectious psudo organisms, language is the medium of transport, the playpan called our mind is theri nutritive medium and growing ground.
Observing nural structural similarities amoung indivisuals having similar knowledgre, andother form of memmory couuld reveal what structures corrospond to what piece of information. That way this information can be used for various pourpouses like knowing tye kinds of thoughts people have, highly helpful for psychologist who could. Rely on a software to detect and determine what kind of environment the patient is in and what kind of worries are present by observing the nural structure.

We could maybe then with thia databases check mycelium colonies structure and see what that reveals, see roots structure and see what that reveals.

Hahah Power of perspective and magnification ;)
Forgive my spellings

I like your poetic perspective. Certainly some interesting, forward-looking ideas. There is research being done with different brain scanning techniques such as fMRI which give some insight here. Being able to create a database of specific information being stored based on structural or even activity scans would be very difficult, as even if two people had exactly the same memory, it's representation in their brains would be different as it depends on their entire life experience up to that moment.

well how about brain scanning newly born children? that might reveal something, if nural networks physically develop over time wouldn't it?
we can compare the different complexity of the brain structure of that newly born kid (control) vs another newly born one subjected to harsh pain ( Experiment ) and see which regions and what structural changes are observed. it isnt ethical but hey, in the name of science what not has been done already XD
I wouldn't personally do it. maybe alter the pain part to something else. maybe keep the kid hungry ? cant try the happy route cause who knows what would make a baby happy., we are so artificial anyway :P

Yes, highly unethical :P That aside, it's a good thought. Thanks for joining the conversation @sishirbaid!
We do know that our brains/neural networks develop as we grow, and we know a good bit about this developmental process. But, there are many difficulties when it comes to memory. Our current technology does not have the resolution to see the relevant changes. If we did, it would still be very difficult and require a deeper understanding than we have to link specific activity causally to a specific experience/memory or vice-versa.

It was a pleasure reading this, something to give hope for people who think or believe that growing old means that the mind and brain start slowly degrading.

The way I see it, that's only because we stop imposing challenges on ourselves, we corner ourselves in the hellish domain we know as "the safe zone" and start rotting when we should be seeking challenges, pushing and punishing ourselves into more situations for our minds to relish in and adapt to, however suffocating, exhausting and complicated they may be.

I agree with you @sandstrider. Of course there are forms of cognitive impairment that may develop regardless of what you do, which is terrible, but I also believe that continually challenging your mind throughout life is a good defense. Never stagnate in "the safe zone!"

Absolutely, cheers!

I always believe that it is possible to continue to learn new things no matter a person age, even though I was told other wise. This article was very helpful, thank you.

Very Interesting post. Thank you for sharing your experience. So does LTP affect gene expression or dose gene expression affect LTP?

Thank you for participating here @psychassist! It's most accurate to say that gene expression is part of LTP. However, in the 2-receptor mechanism from my article, the NMDA receptor activation would initiate a chain of reactions leading to gene expression of proteins which then act to facilitate and make more permanent this LTP event. So, the initial "receptor-stage" LTP event effects gene expression, and gene expression effects the duration and magnitude of LTP. I hope that makes sense :)

Good old memories. Upvoted

So interesting. I didn't know that memories were stored in the connections between neurons. I know that that was something researchers were having a hard time figuring out. Thanks for sharing this post!!

And its still being figured out! We by no means fully understand how memory functions.

Thats a great point. Just like we don't know why we dream yet. It's a complete mystery. Or why we sleep.

Nice post, beautifully presented and explained. detail oriented with nice pics. thank you for sharing this with us, Upvoted

good post,, very nice. keep it @foundation
if you like about poetry visit my post @magicbone172. help me to Upvote and Resteem please. :)

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