Many people suffer from poor memory in daily life and even consider a bad memory as a defect. However, in fact, forgetting is not a bad thing; it is an important protective mechanism that the brain has given to humans.
The book "The Brain of Forgetting" reveals the mystery behind this phenomenon from the perspective of neuroscience. The author, Yasuhiro Iwata, a professor of neurosurgery at Chiba University and a clinical doctor, explains the mechanisms of memory and forgetting in the brain using simple language, challenging traditional perceptions of memory.
People often have misconceptions about memory, such as considering active memorization as a positive behavior while viewing forgetting as a passive occurrence. However, upon closer observation, one can find that some memories are retained without effort, such as the pain of a breakup or the determination to quit a job, experiences often accompanied by intense emotional fluctuations.
This is the essential difference between the human brain and a computer — a computer stores all input information, whereas the human brain automatically filters and judges the importance of information. This filtering mechanism is not under rational control but is a survival wisdom granted by evolution.
In reality, there are individuals with hyperthymesia who can remember every detail, yet they face significant challenges. For example, Kim Peek could count the number of scattered bamboo sticks at a glance, while Jill Price was tormented by nearly 40 years of memories, unable to distinguish reality from the past.
This indicates that if the brain loses its ability to forget, a person would be overwhelmed by an overload of information and might even lose the ability to live normally. From the perspective of energy consumption, the brain accounts for only about 2% of the body's weight, yet it consumes over 20% of the energy. If all information were stored, the brain would collapse due to excessive load.
Memory in the brain has different classifications. From the perspective of neuroscience, memory can be divided into declarative memory and non-declarative memory. Declarative memory refers to memories that can be expressed in words, including episodic memory and semantic memory.
Episodic memory includes temporal and spatial information, such as last week's schedule or someone's name, and these memories are most easily forgotten. Semantic memory is formed through understanding, such as "a day has 24 hours" or "1+1=2," which is more abstract and less likely to be forgotten. Non-declarative memory cannot be expressed in words, including procedural memories like riding a bicycle or using chopsticks, as well as emotional memories such as happiness or anger.
As people age, they tend to shift from prioritizing the retention of episodic memory to prioritizing the retention of semantic memory, indicating enhanced abstract thinking ability, while the ability to remember specific events decreases.
This is a manifestation of the optimization of brain function, not a decline in memory. For example, adults often cannot remember names, but they can grasp complex knowledge systems, which is a reflection of the brain's choice to activate deeper functions.
The brain's memory storage mechanism is closely related to the hippocampus and the cerebral cortex. The hippocampus acts like a "wallet," responsible for storing short-term memory, while the cerebral cortex is like a "bank account," storing long-term memory. Short-term memory in the hippocampus typically lasts only a few minutes unless repeatedly stimulated, which allows it to be converted into long-term memory and stored in the cerebral cortex.
Research on London taxi drivers found that their hippocampal volume significantly increased after memory training, indicating that memory can be improved through training. However, since the brain has limited capacity, it must optimize storage by forgetting.
Forgetting is not only caused by the degradation of proteins over time, but also the result of the brain actively clearing memories. Proteins like Rac1 in the body actively destroy memory molecules, and microglial cells remove inactive neurons to form more efficient neural circuits.
This active forgetting mechanism is crucial for human survival, as it prevents the brain from being occupied by useless information and ensures the efficiency of retrieving important memories.
Emotions significantly affect the retention of memories. The amygdala, adjacent to the hippocampus, generates emotions that quickly form memories. Negative emotions like fear and anger prompt the brainstem to secrete norepinephrine, enhancing the formation of memories, which is why traumatic memories are difficult to forget.
Positive emotions like joy promote the formation of new memories through dopamine secretion from the nucleus accumbens and help eliminate old memories.
Ebbinghaus' forgetting curve reveals the pattern of memory loss: 42% of the information is forgotten 20 minutes after learning, 56% after an hour, 74% after a day, and 79% after a month.
This shows that the fastest rate of forgetting occurs within the first 20 minutes, so efficient review should take place within 24 hours of encountering the knowledge. However, if one wants to alleviate painful memories, they can engage with new information or exercise within 24 hours, prompting the brain to secrete proteins that destroy memories.
The modern phenomenon of "pushing kids hard" poses significant harm to children's brain development. A child's brain is in a critical developmental phase before the age of ten. If exposed to prolonged stress, the amygdala remains activated, leading to excessive secretion of norepinephrine, which damages nerve cells.
More than 30% of teenagers suffer from depression, which is closely related to the inflammatory response in the brain under long-term stress.
Protecting brain health requires scientific use of the brain, with the key being to balance focused thinking and divergent thinking. When engaged in focused thinking, such as studying or working, the brain secretes norepinephrine, but prolonged focus leads to toxic effects on nerve cells.
Divergent thinking, such as daydreaming or taking a walk, helps the brain integrate memories, reduce the number of new neurons, and assist in forgetting negative memories. Both types of thinking need to alternate, for example, after focused study, walking or looking at the scenery to promote memory organization and brain rest.
Methods to improve brain health include sun exposure to promote serotonin secretion, as serotonin is known as the "happiness hormone" and maintains mental stability. Engaging in rhythmic exercise, such as running or chewing gum, promotes serotonin secretion.
Ensuring adequate sleep to avoid the accumulation of metabolic waste in the brain; maintaining a balanced diet, supplementing nutrients such as omega-3; reducing excessive mental strain, avoiding all-nighters or over-immersion in negative emotions.
Technological advancements provide external storage tools for human memory, allowing people to avoid rote memorization of large amounts of information and boldly utilize the brain's forgetting mechanism. However, overuse of mobile phones and other devices can lead to difficulty in switching between focused and divergent thinking, and being in a divergent state for a long time may cause depression. Therefore, it is necessary to use technological products reasonably and maintain a balanced use of the brain.
Forgetting is not the absence of memory, but rather the brain's optimization process. The information that is forgotten does not completely disappear but is transformed into the subconscious, shaping a person's personality and experience.
As stated in the book, "forgetting after reading" is a good reading habit because the input of new memories continuously integrates old experiences, forming a richer cognitive system. Embrace forgetting and use the brain scientifically to keep it healthy and maximize its potential.
Original text: https://www.toutiao.com/article/7516812380286878235/
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