“Time flies, but memories last forever.” I’m pretty sure that you have bumped into this famous caption while you’re scrolling back and forth through your Instagram. But have you ever thought; what are memories, and do they last forever? How do experiences and learning change the connections in our brains and create memories?
Memories are who we are, and making memories is also a biological process. From the very first moment, we witness this world, our brains start to get bombarded by an enormous amount of information about ourselves and the world around us. Hope the curiosity has been awakened to understand memory storage and the triggering factors, reasons why we forget certain events, and many more. Let’s start with the human brain!
The human brain: The least understood part of the whole body
The human brain, actually 86 billion neurons called “grey matter”, is the commander of our nervous system. Sensory organs of the body input the signals, and after processing in the nervous system, it outputs the information to the muscles. These neurons are highly organized to ensure the fine working of the brain. They communicate with each other using neurotransmitters, which are specialized chemicals. Several types are released depending on various factors. This mysterious commander is the least understood part of the whole body due to its unique coordination systems and complexities. The basic functions have been clearly defined, yet the deeper understanding of neural connections and how information gets coded to the chemicals remains a conundrum.
Memory: It’s all about connections
Do you remember your mom’s, or maybe your best friend’s, number to dial? Can you go back to the exact moment your advanced level results were released and imagine the picture mentally? Yes! Those are all memories. What exactly is a memory in scientific terms? It can be defined as the encoding, storage, and retrieval of past learning or an experience.
When we encounter something, it could be even as simple as someone’s name, we form connections between neurons in the brain. Synapses, the junctions between two nerve cells, consisting of a minute gap across which impulses pass by diffusion of a neurotransmitter, create new circuits between nerve cells while remapping the brain. Each of the brain’s 86 billion nerve cells can have thousands of connections to other nerve cells, giving the brain enigmatic flexibility.
Those synaptic connections can be made stronger or weaker depending on how often we’ve been exposed to and activated an event in the past. Activities we are more exposed to tend to form stronger connections, whereas those that aren’t used form weaker connections, and these can even disappear entirely with time. If you are a student who is studying, you must have surely experienced this, and that is why refreshing the memory is important.
Types of memories: A bit deeper
As humans, we retain different types of memories for varying lengths of time from the day we were born. Looking into the depth of memories, two types can be declared, mainly as long-term and short-term memories. Short-term memories have a time span lasting from a few seconds to hours, while long-term memories are stored in the brain for years. Short-term memory can become a long-term memory through a strengthening process called memory consolidation. Individual neurons can remodel themselves and pass on the signals differently, and this stabilizes the memory. If this short-term memory isn’t consolidated, they are discarded.
You must have used the technique of rehearsing or repeating the same thing over and over again to remember the multiplication tables in small ages or to memorize the periodic table. This is an example of using the working memory which lets us memorize something for some time by repeating it.
Memory can be categorized in the aspect of whether you are consciously aware of it or not. Explicit memory, also known as declarative memory, requires a conscious experience. These memories can be either episodic or semantic.
Semantic: These are facts of common knowledge, such as the earth is a planet and the capital of the United Kingdom. They are updatable when a piece of new information is met. Forgetting happens when these new facts settle without cognition.
Episodic: These memories are the events one has experienced in life, such as your bestie’s childhood birthday party, the first day of university, etc. The interesting fact is that the brain can edit these memories with time when we recall them, and the more the emotions and the number of sensory stimuli involved, the higher will be the ability of the brain to retain these episodic memories.
Implicit memory, or the non-declarative memory, is built up unconsciously. Can you ride a bike, drive a car, or play a musical instrument? Those are implicit memories that are mostly procedural. Once you’ve learned, you are not likely to forget.
Where are memories stored in the brain?
In the early days, scientists strongly believed that the whole brain was involved with memory formation and storage. After constant research, it has been found that our brain has many different compartments and specific neurons that work differently to form and store memories.
For explicit memories, there are three major areas of the brain: the hippocampus, the neocortex, and the amygdala.
Hippocampus: This seahorse-shaped part of the brain’s temporal lobe is the place where autobiographical memories of life events are formed and stored for later access. It is also the primary regulator of the memory retention process. Suppose, due to a dire turn of events, one of your close friends had to have most of his hippocampus removed. Your friend will only be able to form episodic memories that last for a few minutes. He will be completely unable to permanently store information and his memory will be limited to the events that only occurred years before his surgery. This shows how crucially important the hippocampus is for laying down memories.
Neocortex: This is a sheet of neural tissue and the largest part of the cerebral cortex. It is the center for higher brain functions such as perception, decision making, spatial reasoning, and language. The temporarily stored semantic memories, such as general facts, in the hippocampus, can be transferred to the neocortex over time.
Amygdala: This pair of small almond-shaped regions found in the brain’s temporal lobe helps to regulate emotion and attach emotional remembrances. Strong emotional memories associated with shame, joy, love, or grief are made permanent with the interactions between the amygdala, hippocampus, and neocortex, and stabilize them. Additionally, this structure plays a major role in fearful memories, which are formed after only a few repetitions. Scientists are still working on discovering how amygdala processes work fear as this could be used to treat post-traumatic stress disorder (PTSD) which affects even most professionals. Anxiety in learning situations is also likely to involve the amygdala.
Implicit memories are formed with the involvement of two major parts of the brain, the basal ganglia, and the cerebellum.
Basal ganglia: These structures lie deep within the brain, and they are particularly involved in coordinating sequences of motor activity that would be important when playing your favorite musical instrument, remembering the dancing steps you practiced or playing football. The impaired movements of Parkinson’s patients are due to the basal ganglia being affected.
Cerebellum: Have you tried eating with chopsticks while you’re dining? The separate structure at the rear base of the brain; the cerebellum, is important in fine motor control like using chopsticks.
The prefrontal cortex is involved in many complex cognitive functions. This part sits at the very front of the brain and is a part of the neocortex. Studies have shown that the prefrontal cortex is involved in tasks that require people to have a short-term memory, such as the location of something. The function of this between the left and right sides is known to be different. The left side is more involved in verbal working memory, while the right is more used in spatial working memory.
Sleep: Why is it important?
We have seen doctors and even many experts say that “Sleep is a good investment”. Sleep is a must for memory storage. During your sleep, the hippocampal neurons that were active during an experience become activated over and over again in a time-compressed manner and replay the recent events to the neocortex. This careful dialogue updates the neocortex and memory consolidation occurs. By skimping on sleep, you are interrupting this process, and the brain won’t be able to consolidate memories.
Memories are who we are. In the past half-century, the understanding of how exactly our brains remember has taken huge leaps. However, the brain remains the most complex and challenging scientific puzzle that still has a lot to decode. The mystery is yet to be discovered.
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