Updated: Dec 22, 2022
When we think of memories, visions ranging from a faded recollection of tearing up Christmas presents, packaged in themed wrapping papers during childhood, to a math question the teacher solved in class can cross your mind. You might remember your 18th birthday or the first day you stepped into the halls of the university, yet, can you recount the events of a random day that you have spent during your university life? Every thought regarding memory boils down to understanding the working mechanisms and determinants of memory.
What comes to mind when talking about memories are images, moments, and incidents as if going through a photo album or watching old DVDs. However, memory is not stored in mind like how photos are stored on an album or videos are recorded in a camera. In fact, memory is nothing of sorts and is simply the reactivation of a specific group of neurons. Memory can be in varying forms and is dependent on its specific neural system.
While a synapse is a junction where two neurons meet and communicate, the connection between two neurons and persistent changes in the efficiency of how they interact is called synaptic plasticity. The stronger the synapse is, the easier the communication between neurons. The changes in plasticity can also vary with time: long-term and short-term.
When speaking of memories that we use over a period of time and visit again at later times, instead of just using a memory once for a specific occurrence, we are talking about long-term synaptic plasticity. How much those memories last can vary, be it hours, months, or years. Overall, remembering which numbers to put into the calculator while solving a math equation or copying down notes on the board can be considered short-term memory while actually recalling certain people, events, etc. is long-term memory. Therefore, while making memories, we mostly value the long-term (“What Is Synaptic Plasticity?”).
Long-term memories are used to store information for a long period of time, unlike short-term memories, which handle information for 15 to 30 seconds (How Long Is Short-Term Memory? Shorter than You Might Think). Memories are also classified in other ways, such as according to behavioral impacts. Declarative, also known as explicit, memories are the ones we can recall for certain events, incidents, people, and details while procedural memories, also known as implicit memories, as the name suggests, hold memories of a procedure or a skill. For example, an explicit memory can be recalling your birthday a few years back, and an implicit memory would be remembering how to play the violin.
However, as much as memories are classified this way, this does not change how interlocked and fragile they all are. Especially while they are still undergoing the process of rearranging to digest the new input (The Neurobiological Bases of Memory Formation: From Physiological Conditions to Psychopathology). And the more synapses are used to recall a memory, the stronger they get and the more the memory will last in the mins and the less it is thought about, the less those synapses are used, and the memory gets weaker until it disappears.
A real-life problem this presents is: should memories be trusted? Considering the nature of memories, they can be rearranged and often forgotten if not thought about enough. Well, how should the idea that they are unreliable and the instances that the use of memories is crucial be reconciled?
In a social experiment by BBC, the reliability of memory and how they were formed was questioned. In this experiment, a scene of the murder was replicated in front of various people in a restaurant. After the fight broke out, the fake murder took place, an ambulance was arranged with “medics” to take the “injured person” and people were brought in to question the event by scientists going undercover as so-called police. Although the incident was fake and no one died, the people who were questioned were sure that someone had died and told the situation as they witnessed it (Can YOU Spot the Murderer?).
Why was that? In the experiment, through leading questions, the medical jargon they heard and the fake situation they experienced was enough for them to think as though the mas were somehow stabbed.
This experiment showed that episodic memories, or memories that “contain events that happen to an individual specifically” (How Memories Are Made: Stages of Memory Formation) could be altered by reactivating those neuron systems differently. Through various inputs of the people in the experiment, all of their testimonies varied systematically, and they were led to giving false testimonies which they believed to be true wholeheartedly. To speculate, the various feelings or situations people were in seem to be able to change the accuracy of their memories.
Overall, memories are a system of connected neurons that become active as they are recalled. However, these connections can be altered, weakened, or even false information could be the backbone of memory as happened in the experiment. People were given a set of stimuli and fabricated information, which they interpreted as a real murder.
In my opinion, this could also be linked to theories of forgetting. The first theory is that when a memory is not repeated, it eventually deteriorates; and the other is that when new information is given, the old information in the brain is replaced (How Memories Are Made: Stages of Memory Formation) The experiment is more relevant to the second theory, considering that the new information in the case of the experiment was the medics arriving and listing injuries as they tend to the “victim”.
These networks can be deceiving depending on the conditions they were formed and how they evolve over time, and I believe that this experiment demonstrates just how imaginative and complex the human mind is regarding storing and processing input, and any research regarding them is mind-blowing.
“What Is Synaptic Plasticity?” Queensland Brain Institute - University of Queensland, 17 Apr. 2018, https://qbi.uq.edu.au/brain-basics/brain/brain-physiology/what-synaptic-plasticity.
Bisaz, Reto, et al. “The Neurobiological Bases of Memory Formation: From Physiological Conditions to Psychopathology.” Psychopathology, U.S. National Library of Medicine, 2014, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4246028/.
“Can YOU Spot the Murderer? - Eyewitness - BBC Two.” BBC, YouTube, 14 Apr. 2010, https://www.youtube.com/watch?v=v_QbTX2qS10. Accessed 9 Dec. 2022.
“How Memories Are Made: Stages of Memory Formation.” How Memories Are Made: Stages of Memory Formation | Lesley University, https://lesley.edu/article/stages-of-memory.
“How Long Is Short-Term Memory? Shorter than You Might Think.” Academic Resource Center. | Duke Academic Resource Center, 13 Apr. 2017, arc.duke.edu/how-long-short-term-memory-shorter-you-might-think.
Image: Source: ليلي جبريل, CC0, via Wikimedia Commons. https://upload.wikimedia.org/wikipedia/commons/8/8f/Books-book-pages-read-literature-159866.jpg