Factors influencing memory retention- the role of trauma, neurobiology and cognition in shaping remembering and forgetting

Hindu College Gazette Web Team
2 days ago
7 min read

Memory is defined by psychologists as the mental faculty and processes for encoding, storing, and retrieving information, which includes past experiences, knowledge, and skills. Our memory includes not just our life experiences and events but also stores basic skills like walking, which allows for automatic execution of learned motor skills without conscious thought, allowing individuals to perform such daily life activities without having to recall each step.

Memory can be categorised into STM (short-term memory) and LTM (long-term memory). Short-term memory, or working memory, refers to the ability to hold information in our minds for a brief time and work with it, whereas long-term memory can be grouped into episodic memory (i.e., the ability to remember episodes of our life) and semantic memory, which is often known as the storehouse of permanent knowledge, like words, concepts, and numbers.

How does memory work?

There are three necessary stages in the learning and memory process: encoding, which is defined as the initial learning of the information; storage, which refers to maintaining information over time; and retrieval, which is the ability to access information when you need it.

Richard Atkinson and Richard Shiffrin proposed a multi-store model (1968) to explain the memory process. According to the theory, any information exists in one of the 3 states of memory—the sensory, short-term, and long-term stores. The theory further postulates that information passes from one stage to the next the more we rehearse it in our minds, but can fade away if we do not pay enough attention to it. We gather information through our senses; for instance, we might hear a piece of music, and if it catches our attention, then our contemplation of this information—known as rehearsal—leads to the data being promoted to the short-term memory store, where it will be held for a few hours or even days in case we need access to it. If the information is rehearsed even more, it gets promoted to the long-term memory store.

Because our surroundings consist of a huge amount of data, we only remember a small portion of it, so if any information doesn't catch our attention, we are prone to forgetting it. The key attributes of long-term memory include distinctiveness and emotional content. Often when a person possesses vivid memories of a certain life event, it is because the event was distinct and contained an emotional impact for the person.

The neurobiological bases of memory

There are various parts of the brain responsible for the mechanisms of memory formation and consolidation. On the basis of neurobiology, memory can be divided into declarative (explicit) and procedural (implicit). Explicit memory is conscious and refers to the information regarding places, things, people, and events. Explicit memory is stored in the medial part of the temporal lobe of the cerebrum and hippocampus and is subdivided into episodic or autobiographic memory and semantic memory. Implicit memory is recollected unconsciously and hence is called non-declarative—it is stored in various regions of the brain like the cerebellum, the neocortex, the striatum, the amygdala, etc.

The hippocampus temporarily holds any new information, acting as a hub that links together different pieces of the memory. The hippocampus generates neural patterns, known as sharp wave-ripples (SWRs), which replay the recently learned information, especially during sleep and periods of quiet wakefulness. These SWRs coordinate actively in other brain areas, particularly the neocortex. The hippocampus drives the reorganisation of information in the neocortex, gradually strengthening the connections between these cortical regions. Over time, this repeated replay and cortical coordination lead to the memory becoming stable and independent of the hippocampus. The memory is then stored within the vast network of the neocortex, no longer needing the hippocampus to be retrieved.

The physiology of memory

The physiological basis of memory involves changes at synapses, the junctions between neurons, where chemical signals are transmitted by neurotransmitters. These changes include alterations in synaptic strength, the growth of new synaptic connections, and modifications to existing ones. Key processes like long-term potentiation (LTP) and long-term depression (LTD) make synapses more or less effective, enabling the long-term consolidation of short-term memories into stable forms. Neurotransmitters such as glutamate play a critical role in triggering and modulating these synaptic changes, with their levels and activities influencing the overall process of memory storage and recall.

Memory and cognition

Memory is a fundamental component of cognition, acting as the process of acquiring, retaining, and retrieving information. Cognition encompasses a broader range of mental processes, including thinking, attention, problem-solving, and decision-making. Memory is essential for nearly all cognitive activities; for instance, working memory holds information temporarily, which is crucial for reasoning, language, and problem-solving. Without memory, cognitive functions like learning, perception, and the ability to form a coherent sense of self would be impossible.

Research suggests that memory and attention are essential processes for learning, and developing the cognitive capacity for these two processes, especially at a younger age, can help students strengthen their academics. Techniques such as chunking, i.e., combining individual units of information into larger blocks, such as remembering a phone number as a combination of two- and three-digit numbers rather than ten individual digits, can improve working memory and hence facilitate the learning process. Another technique spaced repetition which refers to reviewing material at increasing intervals over time also improves long term retention and memory

Memory loss—dementia, diseases, injury, and ageing

A general term used for memory loss is "amnesia", which refers to the unusual forgetfulness of facts, information, and experiences that a person could normally recall. Memory loss can be acute or progressive and results in not just loss of information and knowledge but also a loss of identity that is often closely attached to past experiences. Our personal memories of past experiences shape our sense of self, and hence individuals suffering from a memory-related condition often report going through disorientation and identity confusion.

While forgetting certain things and experiencing difficulty in recalling events as quickly can be a normal part of ageing, noticeable forgetting, i.e., complete failure of recall of events and facts, can be a symptom of an underlying condition. Certain injuries to the brain might result in memory loss, like brain tumours, major surgery, and even cancer treatments such as brain radiation and chemotherapy. Not just physiological reasons, but certain psychological illnesses such as bipolar disorder, depression, or mental health conditions like schizophrenia may also result in memory loss.

Other memory-related disorders include Alzheimer's disease, which affects not just memory but also thinking, behaviour, and the ability to do everyday tasks. Another condition—cognitive impairment—leads to issues with remembering things, concentrating, making decisions, and solving problems. Creutzfeldt-Jakob disease (CJD)—a rare disease that also affects the brain and causes problems with thinking and movement. CJD symptoms quickly get worse and usually lead to dementia and then death within months.

PTSD and memories—is there a link?

The DSM-5 definition of PTSD recognizes that trauma can lead to extremes of retention and forgetting; terrifying experiences may be remembered with extreme vividness or totally resist integration. Pierre Janet, in 1889, first wrote about the correlation between trauma and memory. Since the study of traumatic memories challenges several basic notions about the nature of memory, like that memory is always a constructive process and that memory is primarily declarative (i.e., that people can articulate what they know in words and symbols), certain experiments have been held to research more into the field, resulting in interesting findings.

Certain people display the “re-experiencing” symptom associated with PTSD more than others, and those who do tend to remember more trauma than they experienced, i.e., memory amplification. After a traumatic experience, intentional remembering and unintentional remembering may introduce more details that, over time, can be assimilated into the memory of the event. Research also suggests that traumatic events are more susceptible to memory distortion.

While trauma might result in physiological symptoms like muscle pain, sleep, and certain autoimmune disorders, recent studies reveal that PTSD can dramatically alter the formation and processing of memories. A group of researchers found that, after a traumatic event, the brain strengthens cue-threat associations while undermining episodic memories.

Due to the negative impact and stress of PTSD, some people might experience impaired memory. Trauma can result in profound effects on memory; sometimes memory loss can be a coping mechanism to deal with the difficult feelings associated with a traumatic event.

Memory as a therapeutic tool

A technique called memory reconsideration is used in psychotherapeutic treatment to modify the traces of dysfunctional emotional learning, consolidated through respondent conditioning, found in implicit memory throughout an individual's life. It is a treatment that alters the emotional impact of distressing memories, such as those in post-traumatic stress disorder (PTSD), by reactivating them in a labile state and updating them with new information. This is often done with a beta-blocker medication, like propranolol, to block the reconsolidation of the fearful memory and reduce its emotional intensity, transforming it into a less distressing experience.

Identifying and differentiating normal forgetting and memory loss issues

Normal forgetfulness includes temporarily misplacing items, occasional difficulty recalling a word or name, or forgetting the day of the week, as long as these lapses don't interfere with your daily life, work, or ability to maintain social connections. Moreover, forgetting helps us adapt, make better decisions and maintain mental flexibility. It filters out unnecessary details, hence freeing up mental capacity for new information and therefore leading to effective cognitive functioning. Forgetting allows us to see core concepts of an event and thus facilitates decision-making.

Not being able to recall information at times is normal and is not a sign of memory loss. There are certain theories that explain such loss of retrieval, like displacement, which suggests that forgetting in short-term memory can happen due to a lack of availability. New information displaces the old information, and hence the theory is called "Displacement". Another explanation is interference theory; it suggests that sometimes old information (proactive interference) might hinder the memory process where old memories interfere with new memories. Retroactive interference, i.e., forgetting a previously learnt task due to a new task, can also hamper the memory process.

Sometimes repetitive forgetting or troubles in remembering information can also be a sign of recurrent stress. However, if the memory problem persists, is recurrent and an individual finds themselves unable to recall information at all that they could previously recall, it's best to consult a professional to determine if it's a more significant issue.

Conclusion

Memory is a multifaceted process influenced by neurobiological, physiological, and psychological factors. Key elements like focused attention and information distinctness significantly impact memory rehearsal and retention. Furthermore, the hippocampus and amygdala, crucial brain regions, facilitate memory retrieval, while synapses (nerve endings) respond to new information.

Memory retention is essential for cognitive functions like learning and basic life skills like walking. However, external factors such as head injuries, mental health conditions, and diseases like Alzheimer's can impede cognitive abilities. Recent research highlights the significant impact of PTSD on memory formation and retrieval. Lastly, a promising therapeutic approach, memory reconsolidation, aims to alter the emotional impact of distressing memories, offering new hope for trauma patients.