Memory
What is Memory?
Memory is a process in your brain and body that encodes events, emotions, knowledge, and sensory information into your brain so that it can be recalled later. Memory is a selective and complex process. Not all events you experience will be encoded. Memories that are encoded tend to be more novel (novel meaning new to you, different than other experiences) and relevant or significant to you.
Although memory uses multiple parts of your brain, it is most located in the hippocampus and related areas.
(source).
Types of Memory
Sensory memory
Sensory memory stores sensory information for a very short period (less than a second in most cases), including taste, touch, smell, hearing, and sight. Sensory memory can store multiple pieces of information but generally a new sensory memory will replace old ones. Example: When you notice that the volume of the TV has changed, you’re using sensory memory.
Working memory
Working memory temporarily stores information so that you can process it and make decisions or take actions based on it. It can only hold a little bit of information at a time and usually only holds information for 30 seconds or less. Example: When you calculate a tip in your head, you’re using working memory.
Short-term memory
Short-term memory temporarily stores information so you can access it but does not allow you to manipulate it. There is some controversy about whether short-term memory really exists separately from working memory, and psychological testing typically focuses on working memory and long-term memory only. Example: When you see a phone number and then immediately dial it, you’re using working memory.
Intermediate memory
Intermediate memories are stored for three hours or less. If the memory lasts longer, it has entered into long-term memory. Example: When you drive somewhere for the first time, and then remember how to drive home an hour later using that information, you’re using intermediate memory.
Long-term memory
Long-term memory stores information for an indefinite period. It can hold as much information as you need, unlike working or short-term memory. Example: When you remember your mother’s birthday is coming up, you’re using long-term memory.
Types of long-term memory
Implicit memory:
Memories that are stored and recalled unconsciously.
- Procedural memory: Memory of how to do things, like riding a bike.
- Emotional memory: Memory of events that are associated with very strong emotions, like having a fight with a loved one.
- Priming: Information in your environment you don’t consciously notice but cause you to react differently to something else, either in the present or future, like if you see mold and then immediately see a burger, you’re more likely to be repulsed by the burger.
Declarative or explicit memory:
Memories you can consciously recall.
- Episodic memory: Memories of events, like a specific interaction with another person.
- Semantic memory: Memories of facts, like important dates.
- Autobiographical memory: Memories of personally important or impactful events. This includes internal experiences, like realizing you are in love.
Stages of Memory
Encoding
Encoding is the first step to creating a memory, and usually occurs during the working memory or short-term memory phase. When information is encoded, it is translated from the original information to a more “bite size” set of information that prioritizes the aspects of the information that are most important and connects the information to already existing memory structures (creating associative meaning).
Storage
Storage means placing the information within your cognitive system so that it can be recalled when needed. Different memories will be stored in different places depending on when or how much it needs to be recalled. So for example, if you need to remember a phone number but only long enough to dial the numbers, it’ll be in your short-term memory. But if you need to remember your mom’s birthday every year for the rest of your life, it’ll be in your long-term memory.
Retrieving
Retrieving is remembering- get access to memories that have been previously stored. Recall can happen many ways. It can happen intentionally (you deliberately trying to remember something) or involuntarily (you might recognize something that causes a memory, or be triggered to remember due to your environment).
Cognitive Mapping
Cognitive maps are mental representations of pieces of information. Having a cognitive map helps you remember things, and understand how different pieces of information relate to each other. This helps you understand things faster and prioritize which information to pay attention to.
There are also cognitive maps that people create (on paper or electronically) intentionally- this is not what I’m referring to. This type of map is created unconsciously. Here’s an example:
(source).
Cognitive maps & bias
Cognitive maps are incredibly useful, but they also lead to bias. Cognitive maps help you process information quickly and come to a decision based on your perception of probabilities. This uses a set of heuristics (meaning, a mental short-cut) to help you decide what you think is happening and how to respond. This is mostly a good thing, but heuristics are imperfect and can lead to bias.
For example, the availability heuristic means making decisions (particularly about probability) based on what examples are most available to you in your memory or cognitive map. So for example, if the most available examples of black men are criminal on the nightly news, you are more likely to decide that a black man walking down your street is a criminal rather than a neighbor.
Forgetting
“Forgetting” means that a memory that was encoded into long-term memory can no longer be retrieved. However, people often refer to “forgetting” when they can’t retrieve a past experience that was never encoded or made into long-term memory. This is not accurate- it’s impossible to “forget” something that was never a part of your memory. For example, I am “forgetting” if I can no longer remember a story I used to tell to my friends often. But I am not “forgetting” if I can’t remember an experience I have never remembered.
“Forgetting” can happen for a number of reasons, and most of these are not a sign of anything negative. Memory pruning is a healthy process in the brain, which works to strengthen aspects of memory that continue to be important for your life and to delete aspects of memory that stop being useful. This is the purpose of cognitive mapping. Essentially, the pathways that continue to get used (College -> Favorite Professor -> Important Experience with Favorite Professor) continue to exist, while pathways that aren’t used often get pruned (College -> Mediocre Professor -> Okay Experience with Mediocre Professor).
However, sometimes “forgetting” occurs due to a medical or mental health problem. Memory impairments don’t work the way the media often portrays them- for example, amnesia most often impacts anterograde memory, not retrograde memory.
Sometimes forgotten memories can return. Usually this occurs due to an environmental trigger. For example, if I return to my undergraduate university and see Mediocre Professor, I may recall my Okay Experience with them. Deliberately attempting to recall forgotten memories rarely works- typically remembering happens spontaneously.
There are medications and behavioral treatments to improve memory impairments. These rarely bring back forgotten memories but rather help you forget less over a longer period of time.
Amnesia
Retrograde amnesia
Forgetting memories that happened prior to an injury or illness that impacts memory. Not all old memories will be forgotten- typically episodic memory is most highly impacted, but implicit and semantic memory are often fairly intact. Usually, older memories will be easier to remember than more recent ones. New memories can typically still be stored. Retrograde amnesia is typically not permanent and memories can be restored through treatment and exposure to lost memories. This type of amnesia is often caused by a brain injury, serious neurological illness like encephalitis, and other issues like long-term severe alcohol use.
Anterograde amnesia
Loss of ability to make new memories after an injury or illness that impacts memory. This type of amnesia can be caused by brain injuries like loss of oxygen to the brain (anoxia), serious neurological illnesses like encephalitis, and other issues like long-term severe alcohol use. Treatments cannot repair this type of amnesia but behavioral interventions can help people improve their ability to use procedural memory in their daily lives.
Transient amnesia
Short-term significant impairment in both short-term and long-term memory. This type of amnesia is temporary and has no long-term impacts on people that experience it.
Post-traumatic amnesia
Amnesia caused by brain trauma (like a severe concussion or stroke). This type of amnesia usually impacts memories related to the injury itself and memories stored around that same time (so for example, all the memories that occurred the morning that a person was in a severe car accident). This type of amnesia can be mild and not cause any long term issues, but for some people it is very serious and indicates that recovery from the injury will be longer and harder.
Dissociative amnesia
Psychologically caused amnesia (all others are medically caused). Typically dissociative amnesia is caused by an unconscious response during a traumatic event or by posttraumatic symptoms, which cause the person to stop encoding information. Sometimes these memories are being stored in long-term but not able to be accessed. Sometimes these memories are only stored implicitly (in emotional memory) but not explicitly (in episodic memory). Memories from dissociative states can sometimes be recalled (if they were encoded) but this typically only happens spontaneously and memories are often incomplete.
Dissociative fugue is a type of dissociative amnesia where a person suddenly but usually temporarily loses access to most memories. They often travel away from their homes and create new identities. This is extremely rare.
The Interaction between Emotion and Memory
Emotions impact memory in two major ways: emotions change how information is prioritized for encoding and storage (often picking the information that is most relevant to the emotions) and can impair ability to encode, store, and recall memory. Stress is one of the clearest examples of this. When you are stressed, your body increases release of stress hormones, which impacts your ability to encode memories. People who are stressed learn less. For example, your memory of a time when you were stressed is likely to be mostly focused on the emotional memory rather than the episodic memory, meaning that you will remember how you felt emotionally and physically better than you will remember the specific events. This often occurs within trauma, causing people to remember the emotions associated with the trauma really well but less able to remember the specifics of the event.
The Interaction between Mental Health Issues and Memory
Mental health issues can negatively impact memory ability in a number of ways. For example, sleep impairment negatively impacts ability to consolidate memories so that they are more integrated into your cognitive map and easier to recall. Attention impairments negatively impact ability to encode- if you are not paying attention, you will not be able to encode the information. Cognitive distractions like worry impact ability to encode, store, and recall. These kinds of memory issues due to mental health issues are typically not permanent, and will improve as the mental health issue is improved or appropriately accommodated.
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