Why Do We Remember Things?
To listen to the podcast, click below:
Find us on all other platforms, here:
Memory has been one of the greatest mysteries. It is difficult to understand why it works the way it does.
Why do we need memory?
Before we go how memory works, let’s appreciate the fact that it makes our life easy and worth living. Imagine a life where your memory fades away they moment you go to bed. It would be a bit like the Ghajini situation isn’t it? Not pleasant at all. You wake up and you do not remember who you are or your purpose in life. You would not know what to do next. (Tattooing body might be one option — just saying!)
Our memory helps us not only in our personal life, but also in our social and professional life as well. Without memory you wouldn’t be able to remember your closest friend or family let alone cherish the moments that you would’ve spent together in the past. Memory is one of the factors that determine the depth of relationships that we have. Professionally, well you know how that works don’t you?
Our memory is also deeply connected to our emotions as well. Certain sensory stimuli can trigger a response from our memory. This is pretty much how nostalgia works. When you see something, hear something like an excellent piece of music, taste something or smell something, these actions can trigger a memory and sometimes you end up wishing you were there or otherwise.
But in any case, life would be next to impossible without memory. There are cases where people have lost most of their ability to recall things and we shall look into such cases during the course of this episode.
What is memory?
When we talk or think about memory, we might be used to thinking that it works just like the computer or phone memory. You have these directories or folders within brain within which each memory is saved like a file and is searched and retrieved when required through some way of indexing by the brain. But in fact, things work a bit different. There definitely no drives, slots or ports where memory cards or floppy diskettes are plugged in within our brains!
Our memory is not just a single unit working in creating, storing and retrieving thoughts and events. It is a collective group of different units that work together to work seamlessly in creating, storing and retrieving memory. Within these processes, there are majorly three steps involved — encoding, storing and retrieving
Memory is an informational processing system with sensory processor, short term and long term memory. Sensory processor does the job of sensing an external stimuli. Working memory takes care of the encoding and retrieving and the long term memory takes care of the storing part. This is a bit like how computers work with an I/O device like keyboard that captures the user input. The RAM manages the short term memory and helps in encoding the input signals to characters. The hard drives serve as the long term memory by storing the data.
Sensory Memory
Sensory memory helps in capturing external stimuli and last for little less than a second. This memory rapidly degrades over time and can retain only a small set of information for a very short amount of time. According to an experiment conducted by American cognitive psychologist and researcher George Sperling in 1963, he was able to demonstrate that the capacity of sensory memory was approximately 12 items. This type of memory cannot be improved by practicing. From the point of view of primary sense involved, sensory memory can be divided as follows:
- Iconic memory: Type of memory that briefly stores images.
- Echoic memory: Type of memory that briefly stores auditory information.
- Haptic memory: Type of memory that briefly stores touch information.
Short term or working memory
This type of memory helps us to recall for a period of few seconds to about a minute. Typically a person can remember about 4–7 items with short term memory. However, large set of data can be broken down into chunks of 4–5 items to be recalled efficiently. Phone numbers are easily remembered if they are broken into sets of three or four numbers instead of ten digits.
9999999999 or 999 999 9999 — which one’s easier to remember?
Apologies if that is your phone number! But this is exactly how phone numbers are displayed in some countries. You might have seen this while filling up online forms. I use this format in my signature often!
Also, the short term memory is encoded acoustically by the way they sound. This is why letters with similar sounds are often confused while recalling withing short term memory.
Long term memory
Long term memory has capacity to retain much more information for a much longer duration of time, sometimes lasting a whole lifetime. This memory can be enhanced by repetition and practice. You might be able to remember the lyrics to a song for many years since you might be listening or singing those lyrics multiple times during the course of your life.
Long term memory also stores information as episodic memory where what, when, where and how of the events are answered and thus helps in recalling the events by connecting the answers to these questions. This is how you remember the embarrassing incident that happened during your brother’s marriage and ended up with Monica!
The hippocampus is responsible consolidation of information, but does not to be actually storing it. Alzheimer’s disease and dementia affects hippocampus. Hypoxia can also damage hippocampus. Hippocampus damage results in anterograde amnesia which degrades the ability to create new memories.
Henry Gustav Molaison was a patient who underwent lobectomy to remove most of his hippocampi and some other parts of his brain to cure his epilepsy. This resulted in him losing his ability to create new memories. During his later years, he could fill crossword puzzles with pre-1953 memories. For data post 1953, he started modifying his pre-1953 knowledge.
Some of the long term memory could also be stored as a result of DNA methylation which is a process by which methyle molecules are added to DNA sequence resulting in changing the activity of the DNA segment without changing the sequence.
Storage of memory
For encoding the memory for storage, priority is given to experiences that are consciously given priority. This is the reason that you do not remember the things that are not given priority. Like if you are walking on a street, many people and vehicles pass by you, but you do not remember all of them.
A memory begins with the perception of an event and this is encoded and stored by electro-chemical changes within the nervous system and the brain. All the nerve cells in the body are connected via synapse. It is a structure that facilitates the passage of neuron or chemical signal from one neuron to other or to other cells.There are more than 100 trillion synapses in our body. Let that digest!
These electrical signals are transmitted via charged molecules called ions that move through the length of the neuron. When they reach the end of neuron, this electrical signal gets converted to chemicals. These chemicals are called neurotransmitters. These neurotransmitters are stored in vesicles.
During the transmission through neuron, neurotransmitters are ejected into the synaptic gap and a neighboring neuron catches them. Mitochondria generates a compound called Adenosine Triphosphase that helps in this process.
In all this process, the brain uses immense amount of energy, about 20% of all energy used by the body. Brain has a huge network of neurons and these networks can keep changing all the time. In fact as you have new experiences in life, the brain keeps changing these connections and the structure of the network keeps changing.
These networks help in creating long term memory. When you repeatedly experience something like practicing to drive a car, you are exercising the same brain cells and connections again and again. After a while, the connections becomes so strong that you start driving perfectly. But if you give up on practicing, the brain slowly loses these connections and you might not be perfect anymore.
Sleep and memory retention
According to studies, sleep helps in memory retention. This is because, during sleep, the neural connections are strengthened within the brain. Memories are reactivated during sleep and hippocampus replays the day’s events for the neocortex which is the part of the brain that is involved in sensory perception, cognition, generatio of motor commands, spatial reasoning and language. Neocrotex then makes the decision on the memories that need to move into long term memory.
Sleep deprivation can lead to difficulty in retaining and extracting memories since the above mentioned consolidation does not happen properly. The neural connections are not strong enough and sometimes results in corrupted memories as well.
So, don’t lose your sleep over that test kids, you might just end up forgetting whatever you’ve learnt!
Image: Unsplash
Originally published at https://www.writerandgeek.com on November 8, 2019.
Listen to my podcast Writer & Geek
Find us on all platforms Find Writer & Geek
