How Your Memory Works

"Sherlock Holmes, the famous detective, once compared the human brain to an attic, suggesting it had limited memory storage. His loyal companion, Dr. Watson, once mentioned the Earth orbiting the sun, to which Holmes humorously replied, 'Now that I do know, I shall do my best to forget it.'

Holmes argued that filling one's mental attic with random facts and trivia left little space for more important tasks, such as discerning subtle differences between deadly poisons.

But was Holmes correct? Is human memory truly confined like a computer's storage, or is it boundless? And what if perfect memory were possible? How would it reshape our lives?

In the animated film 'Inside Out,' memories are portrayed as glowing spheres neatly organized in the brain, resembling books in a library. However, the reality of memory is more intricate. Unlike a centralized memory bank, individual memories are scattered throughout the brain.

Multiple brain cells across different regions collaborate to construct a single memory. For example, remembering the taste of grandma's apple pie engages various cells for visual, olfactory, and gustatory aspects.

In reality, memory isn't a physical entity residing in specific brain cells; it's an active process, not a tangible object. Think of fans at a baseball game doing 'the wave.' No single fan embodies the wave; its magic happens when all spectators coordinate in a specific sequence.

Similarly, memory emerges when interconnected neurons fire in precise patterns. Since these cells can produce diverse patterns, a single group of neurons can encode multiple memories, expanding the brain's memory capacity.

Buried deep in the brain lies a cluster of cells shaped like a seahorse, dubbed the 'hippocampus' by 18th-century scientists. Without this seahorse-like region, remembering would be challenging. Our understanding of memory owes much to an anonymous patient known only as H.M.

In 1953, H.M. underwent epilepsy surgery that removed most of his hippocampus. For the rest of his life, he grappled with severe amnesia, unable to form new factual or event-based memories. However, he retained pre-surgery knowledge, revealing that while the hippocampus is essential for memory formation, it isn't where memories reside.

So, how do experiences become memories? Imagine examining a mouse's brain as it navigates a maze. We could map which brain cells activate as the mouse encounters different maze elements.

Later, we might observe these same cells replaying the experience, strengthening connections through rapid playback—a process called consolidation, how animals, including humans, transfer new memories to long-term storage.

Days or weeks later, a specific scent could trigger the same cell patterns in the mouse's brain, recalling maze memories, much like how the scent of cinnamon might evoke memories of one's grandmother. However, the brain's memory formation isn't foolproof.

Mentally rehearsing imagined scenarios can feel as vivid as real experiences. Creating a detailed mental image of a crime scene based on descriptions can activate similar brain networks as actual experiences. Repeated mental rehearsals can solidify these imagined scenarios into false memories, as detectives sometimes unintentionally do with witnesses.

While humans excel at remembering, we're also skilled at forgetting, using various methods. One form of forgetting involves memories gradually fading over time, known as 'passive oblivion.' Connections between brain cells weaken, or essential memory triggers like sights, sounds, and smells diminish.

Another form, 'targeted forgetting,' occurs during sleep, as the brain clears redundant or outdated information from the day. Sleep-induced stages selectively trim and prune cell connections while erasing unnecessary memory circuits.

The third form, 'motivated forgetting,' is when individuals intentionally suppress unpleasant memories. This helps regulate emotions and maintain focus on the present, preventing dwelling on negative past experiences. The mechanics of motivated forgetting remain unclear, but a part of the brain seems to block retrieval of distressing memories.

Our brains use these forgetting mechanisms because forgetting is essential to human cognition. Forgetting allows recovery from traumatic life events, and conditions like PTSD may arise from an inability to forget.

Additionally, forgetting helps eliminate superfluous information, preventing neural networks from becoming overwhelmed with trivial details, as Holmes once surmised. It also enables us to replace outdated beliefs with updated information, enhancing our mental models of the world.

Occasionally, we hear stories of individuals who never forget anything, a rare condition known as hyperthymesia. The most famous case is Jill Price, an American woman who exhibited near-perfect memory recall from the age of 14.

Jill vividly remembers details of any past date, including clothing, meals, and significant historical events. Her memories play like enhanced video reels, complete with smells and emotions, regardless of when the events occurred.

While this might seem like a gift, Jill describes the burden of haunting memories and regrets. Unlike most people, she remembers every choice and its outcome, an unending mental record. There are moments we all wish to forget, like cringe-worthy high school memories that resurface at the most inconvenient times. Can these unwanted memories be erased?

In an episode of 'House, MD,' electroconvulsive therapy (ECT) was depicted as a method to treat patients plagued by painful memories. ECT involves controlled electric shocks to the brain, which can lead to memory loss.

However, ECT doesn't always selectively target the memories one wishes to forget. Erasing memories in humans remains more akin to using a hammer than a scalpel.

Our ability to forget, like our capacity to remember, is a finely tuned and intricate mechanism. If humans couldn't remember and learn from pivotal events, our species might not have endured. Paradoxically, the ability to forget is equally crucial, integral to navigating the enigma of life.

So, while achieving perfect memory and never forgetting anything may remain beyond reach, it raises the question: Is memorization the most effective approach to learning? While memorization can serve as an initial step in grasping new concepts, true understanding demands more.

It involves recognizing connections between concepts, exploring various interpretations, and adapting to new information. These skills foster genuine learning, and for those looking to hone these abilities, platforms like Brilliant could be invaluable."