By Ashna Chaturvedi
The concept of memory has long been one of mass interest and speculation among both the scientific community and the general public. Memories are one of the key constituents of individual identities and are also one of the key cornerstones of human relationships. So, what is memory? And, how are they formed?
Well, memory has 3 main definitions. (Spear & Riccio, 1994) First, it can be considered a ‘store’ where information about experiences is kept. Secondly, in neuropsychology it’s described as an ‘engram,’ which is a ‘memory trace’ that can act as a change in the biochemical/biophysical makeup of the brain. Lastly, the concept of memory can also be perceived as the process through which information is stored and retrieved. Memory can also be classified into sensory, short-term (associated with consciousness) and long-term memory.
Memories are formed due to the reactivation of a certain group of neurons. The ‘strength’ of memory is controlled by synaptic plasticity which is reliant on the connections between the neuron. It is also linked to the likelihood of a neuron combination being reactivated. Depending on how often they have been activated or are linked with a memory of the past, the bonds between the neurons are likely to be stronger. It is ultimately the strength of these connections which determine whether a combination of neurons will be activated over a different combination; “Active connections tend to get stronger, whereas those that aren’t used get weaker and can eventually disappear entirely.” (Queensland Brain Institute, 27.7.2020)
In the hippocampus (pictured above) - a seahorse shaped structure located in the inner region of the temporal lobe (towards the middle of the brain) - new neurons can be formed through the process of neurogenesis. Studies of mice brains have also shown that there may be a correlation between the levels of neurogenesis and levels of memory formation.
In addition to being the location where neurogenesis occurs, the hippocampal region forms a key part of the limbic system: a system that processes memory and emotion.
Henry Molaison (referred to as Patient H.M. during the time he was alive) had his hippocampus removed during an experimental epilepsy treatment surgery in 1952. The result was that he became amnesiac and suffered partial memory loss. This then led to the discovery that the hippocampus was a crucial memory formation structure. Interestingly enough, subsequent studies and experiments showed that this memory loss was ‘far from simple.’ (Psychology Today, 2.8.2020) Although he could no longer remember any short-term memories, such as who he was talking to a minute ago; his age; the current president; or the words he had just filled out in a crossword puzzle; he was capable of learning ‘sub-conscious’ motor skills like learning to walk on crutches after spraining his ankle. He also was able to remember things prior to his surgery, also known as long term memories, like memories from his childhood and the name of the president in office at the time of his surgery. (Dwight D. Eisenhower was his response)
Original Source: Duke University
Patient H. M’s contribution to the field made him the “the most studied case in medical or psychological history.” (Psychology Today, 2.8.2020) and the discovery that there may be a distinct separation in the formation of long-term vs short term memories and conscious vs unconscious memories has definitely contributed to constant flow of new research being published on the exact process + locations of memory formation and storage, respectively.
References:
Qbi.uq.edu.au. 2020. How Are Memories Formed?. [online] Available at: <https://qbi.uq.edu.au/brain-basics/memory/how-are-memories-formed#:~:text=Memories%20occur%20when%20specific%20groups,or%20less%20a%20particular%20sequence.&text=Memories%20are%20stored%20by%20changing%20the%20connections%20between%20neurons.> [Accessed 2 August 2020].
Encyclopedia Britannica. 2020. Hippocampus | Definition, Location, Function, & Facts. [online] Available at: <https://www.britannica.com/science/hippocampus> [Accessed 2 August 2020].
Gallagher, J., 2020. Rules Of Memory 'Beautifully' Rewritten. [online] BBC News. Available at: <https://www.bbc.com/news/health-39518580> [Accessed 2 August 2020].
The Human Memory. 2020. Types Of Memory | Different Brain Memories Facts, Jobs. [online] Available at: <https://human-memory.net/types-of-memory/> [Accessed 2 August 2020].
Catalogue.pearsoned.ca. 2020. [online] Available at: <https://catalogue.pearsoned.ca/assets/hip/us/hip_us_pearsonhighered/samplechapter/0205734820.pdf> [Accessed 2 August 2020].
Catalogue.pearsoned.ca. 2020. [online] Available at: <https://catalogue.pearsoned.ca/assets/hip/us/hip_us_pearsonhighered/samplechapter/0205734820.pdf> [Accessed 2 August 2020].
Edited by: Simoni Shah and Noelle Darts
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