Luis C.

1/31/25 - 3/18/25

1. Introduction

Deja Vu is a commonly reported phenomenon that you or I have experienced at least once in our lifetime,

unless you’re a part of the 20-40% of people that have reported to never have experienced Deja Vu.

What is Deja Vu? Deja Vu can be described as a feeling of having experienced the present situation, says the Oxford Dictionary.

Deja Vu - A feeling of having already experienced the present situation.

Although it’s fun to speculate and believe that Deja Vu is a result of the existence of alternate realities or a past life, I personally think that it’s far from the truth.

To my personal belief, “Deja Vu” can be chopped up to a mishap in the firing of neurons in the brain.

Such mishaps cause confusion in the brain between the creation and storing of both long and short term memory (Both stored in different regions of the brain).

And don’t be fooled, this is more of a research paper on Memory than it is Deja Vu..

this is the only and last time Deja Vu is mentioned in this paper.

Neurons - A type of cell that receives and sends messages from the body to the brain, and back to the body.

(STM) Short-Term Memory - The temporary storage of information in the brain for a brief period, typically ranging from seconds to minutes.

(LTM) Long-Term Memory - A cognitive system in the brain that stores information for extended periods, often years or even a lifetime.

2. How Does Memory Work?

Throughout every waking second, the brain is processing both new and old information and simultaneously deciding where it needs to be stored.

As you process information throughout the day, the brain first begins to process it in its Short-Term Memory(STM) so that it’s readily available for a short period of time.

However within minutes or sometimes up to hours, the brain will decide whether the information is significant enough to be stored in its Long-Term Memory (Think Birthdays, Names, Faces, etc.) and begin to encode it.

Note: Those with dementia suffer from the loss of both Short-Term and Long-Term Memory. However, it is especially common forffg these patients to struggle to remember recent events or in our case what we would call STM. This is because the hippocampus (a brain area crucial to the formation of STM) is the first and most heavily impacted region of the brain.

How long does it take for STM to be stored as LTM?: It can take minutes or up to hours for memory to move from Short-Term to Long-Term

Hippocampus - A brain area crucial to the formation of STM

3. (STM) Short-Term Memory

(STM) Short-Term Memory - The temporary storage of information in the brain for a brief period, typically ranging from seconds to minutes.

• Holds a small amount of information in an active, readily available state for a short period of time.
• Believed that the capacity of STM is limited and can only hold 7±2 items at once.
• Information that’s not studied, repeated, or processed can be quickly forgotten.
• Almost 70% of all information learned is forgotten within the first 24 hours

Short-Term Memory has Three key aspects:

1. Limited Capacity - Can only store 7±2 items at a time.
2. Limited Duration - STM is very fragile and information can be forgotten within seconds if not studied, repeated, or processed.
3. Encoding - If the memory is significant enough, STM is translated to LTM.

STM Varies among individuals and is influenced by different factors such as:

• Attention
• Distractions
• The Nature of the Information

How Does Encoding of STM work? Four Ways STM is encoded:

1. Acoustic Encoding (Sound) - This is the most common form of encoding in the brain and it’s practiced when you repeat something out loud as a way to not forget the information.

Ex: Repeating the Quadratic Formula to yourself over and over whenever you’re drunk to “convince” yourself that you’re sober.

1. Visual Encoding (Picture) - The process of storing visual images and it’s details (https://humanbenchmark.com/tests/memory is a tool for assessing your Visual Memory)

Ex: Remembering the color of her eyes even after it’s been several years since you’ve broke up. You can’t seem to get that image out of your head and it kills you every time you remember it.. Thank your brains Visual Encoding for that!

1. Semantic Encoding (Meaning) - This encoding has to do with processing the meaning of information and plays a dominant role in Long-Term Memory. This is the deepest and most effective form of encoding memory, because the brain attaches meaning to the information we just received. Focuses on the meaning of the memory rather than it’s sound or appearance. Linked to Nostalgia.

Ex: You remember certain facts because of the stories behind it, for example you remember certain facts because of previous conversations you had with a friend or classmate.

1. Tactile Encoding (Physical) - The process of storing and processing how something feels (Physically)

Ex: Remembering the feeling of the first time you held her hand through that rainy night..

4. How Are Traumatic Memories Processed & Stored?

Traumatic memories are encoded differently in the brain, because even though it may have been a significant memory in one's life, due to trauma it often leads to suppression or fragmentation of the memory, and this is all because of how the amygdala, hippocampus, and prefrontal cortex react under extreme amounts of stress.

How does the amygdala respond to extreme stress?: The amygdala becomes overactive during trauma and causes heightened emotion encoding in a disorganized manner, such as fragmenting the traumatic event and breaking it up to a list of sensory-based triggers.

(ie: Why certain people are triggered by certain sensory or verbal actions/cues)

How does the hippocampus respond to extreme stress?: The hippocampus can shut down or be dysregulated by high levels of stress. Instead of the hippocampus doing its intended purpose (organizing memories into a timeline based format) the traumatic event can be fragmented or even blocked from conscious recall which can lead to dissociation. This is how even though a memory is significant, it becomes lost to the conscious brain.

How does the prefrontal cortex respond to extreme stress?: When the prefrontal cortex (PFC) is under extreme stress, it lacks the resources for proper decision making, and its activity decreases substantially. This makes it hard to for the brain to think clearly and perform tasks such as proper decision making and the individual becomes more prone to impulsive decisions as the brain is prioritizing more immediate survival responses. (ie: Why individuals who suffer from disorders such as anxiety and depression find it hard to make proper decisions, think clearly and regulate their emotions because their PFC is in an overwhelmed state and responds by going into a type of “survival” mode.)

• Stress → Impaired PFC Function → Poor Emotional Regulation → More Stress
• PFC - Prefrontal Cortex
• Decreased Activity
• Impaired cognitive functions
• Lack the needs for proper decision making, planning, and impulse control
• Hard to think clearly
• Prioritized more immediate survival responses
• Reduced function
• Makes it difficult to focus and strategize
• Stress hormones are released
• Studies on animals suggest that the PFC goes “offline” during extreme stress

Amygdala - Processes fear and emotional intensity.

Hippocampus - [A brain area crucial to the formation of STM] Responsible for organizing memories into a timeline based format.

(System 2)Prefrontal Cortex - Responsible for rational thinking and decision-making

Fragmentation - The idea that a person’s identity, memories, or emotions are divided into separate parts.

How are traumatic memories encoded in the brain? When a traumatic event occurs, the brain encodes the memory in a strange way.. Rather than encoding it to LTM in a way that is tangible and easy to access, it tends to fragmentate it and reroute the storing of the memory in such a way that they cannot be consciously accessed. It is most likely to resurface in a state of “State-Dependent Memory” where both memories and information are heightened when exposed to the same psychological and sensory state as when the traumatic memory occurred.

State Dependent Learning - The phenomenon of remembering information better when you’re in the same psychological and sensory state as when you learned it.

5. (LTM) Long-Term Memory

(LTM) Long-Term Memory - A cognitive system in the brain that stores information for extended periods, often years or even a lifetime.

• Nearly permanent archive of memories, experiences, and feelings that are stored for long periods of time (From years up to a lifetime!)
• Takes information from STM and stores for later retrieval
• Memories may last a lifetime but the ability to retrieve them may be more challenging.
• Capacity of storage is thought to be unlimited

Why is it harder to retrieve a memory even after it’s been stored in LTM?

Though a memory might be encoded into LTM, an individual may still have difficulties retrieving such memories into their active consciousness because of factors such as:

1. Poor initial encoding - This occurs when an individual is not paying enough attention when a memory is being formed.
2. Lack of Adequate Retrieval Cues - The brain lacks enough information of the memory to trigger it (Neurons are unable to fire and pathways are unable to be made)
3. Interference From Other Similar Memories - One might confuse a certain event with another, confusing details because they have so many other similar memories stored in LTM.
4. Outside Influences of New Memory - How often is it that we learn something and form a memory and learn nothing in between the formation of it and having to recall the information. Almost never.. An individual is vulnerable to the vast amount of information available to him at any given moment, and the brain is constantly trying to encode it.
   1. From Sec. 2 ‘Intro’: “Throughout every waking second, the brain is processing both new and old information and simultaneously deciding where it needs to be stored.”

Note: However it can be challenging to determine if the difficulty of retrieving memory is because of the passage of time or because of one of these outside influences. As current research suggests that about 70% of information that is learned in a given day is forgotten upon the 24 hours of initial learning.

Interference - A memory phenomenon in which some memories interfere with the retrieval of other memories.

• Two types of Interference - Proactive and Retroactive
  • Proactive - When an old memory makes it more challenging or nearly impossible to remember a new memory (Old memories interfering w/New Ones)
  • Retroactive - When new information interferes with the ability to remember previously learned information. (New memories interfering w/Old Ones)

How is LTM Encoded in the brain?

There’re a plethora of ways that any memory could be encoded in the brain, as we listed before from Sec. 3 (STM) - Acoustic, Visual, Semantic, and Tactile. However the principle method of encoding when it comes down to LTM appears to be Semantic Encoding, which is directly linked to the meaning of information. However LTM is also encoded both Visually and Acoustically. **

Compared to STM, which is stored/encoded in the brain sequentially (remembered in the order it was presented to them), LTM is stored/encoded by association which further backs up the idea that the main force behind encoding for LTM appears to be Semantic.

Ex: Have you ever walked into a room and forgotten why you walked into it in the first place? Try returning to the room where the thought originally occurred, and there’s a higher chance that you’ll remember! This is sequential encoding at practice.

Ex: Listening to the same music as you’re studying and taking a test. I’ve personally done this various times without realizing.

ie: Why Exposure Therapy works so well in the first place.

Types of Long-Term Memory

There’re multiple forms of LTM in the brain!? You’re just as surprised as me buddy.. There’re two forms of LTM in the brain:

1. Explicit (Declarative) - Episodic & Semantic
2. Implicit (Non-Declarative) - Procedural & Emotional Encoding

Those are pretty big words I know. What exactly do they mean though? Easy. 1. Explicit includes storing the meaning of words and general information and storing information about events. All explicit/declarative memory involves conscious thought and is where it differs form Implicit/Non-Declarative Memory which is essentially the practice of remembering your motor skills such as remembering how to tie your shoes, what bus to take in the morning, or something like how to play the piano.

Explicit/Declarative Memory - Conscious

Implicit/Non-Declarative Memory - Subconscious

How long is LTM stored for?

Though the duration of LTM after it is encoded is thought to be unlimited, many other influences play a key role in being unable to remember certain events. The main culprit seems to be accessibility rather than availability. We previously touched on why it may be harder recall memories in Sec. 4: “Why is it harder to retrieve a memory even after it’s been stored in LTM?”. One idea is that the passage of time leaves us unable to recall certain events like we used to. This is called the forgetting curve.

Forgetting Curve - The decline of memory retention in time.

• Information is lost over time if there is no attempt to retain it.

The stronger a memory is, the easier it will be to retain and recall upon the passage of time though.

Strength of Memory - Refers to the durability that memory traces in the brain.

• The stronger a memory is, the longer period of time that a person is able to recall it.
  • Stronger memories include:
    • Being easily retrievable
    • A high level of detail
    • Strong emotion association
    • Repeated exposure to the information
    • Deep processing during encoding
    • Significant Personal Relevance

(6) Levels of Processing Theory

Elaborative Cognitive Processing - A learning strategy that involves making connections between new information and what you already know.

Levels of Processing Theory by Craik and Lockhart (1972) - Proposes the idea that there are generally three levels to how deeply information is processed and encoded, leading to how well it is remembered.

1. Shallow Processing - Only involves maintenance rehearsal (repetition which helps up hold something in the STM) and leads to short-term retention of information.
2. Intermediate Processing
3. Deep Processing - Involves as mentioned above “Elaborative Cognitive Processing” which involves a more meaningful analysis of information and leads to a better recollection of information.

“Memory is just a by-product of the depth of information processing, and there is no clear distinction between short-term and long-term memory.”