Our perception of the world, though driven by what we sense in the present, is the culmination of all our past experiences and observations. The skill of being able to encode, store and ultimately recall information is thus crucial not only for decision making but also for creating an identity that lasts through the passage of time. This process, what we call memory, can be broken down into three major parts: sensory, short term, and long term memory.
First, sensory memory: as the name suggests, everything you hear, see, feel, smell and taste falls into this category. Retained for only a few seconds, a barrage of information from one’s senses is sent to the brain. The brain takes all this information and decides what is important, transporting that to short-term memory (what we consciously remember on a given basis that is happening in the moment).
Short-term memory’s limited capacity means only a few items exist in the mind at a given time, and last for about 15 to 30 seconds. Readily accessible, these ‘memories’ are what we perceive as our current thoughts and dissipate easily. The step of encoding is what transfers memory in STM to long-term memory, which has infinite capacity and can last up to one’s lifetime. This depends on whether the memory is recalled in the first few days of entering long term memory, where it goes from the hippocampus to the cerebral cortex.
Finally, long term memory takes on the role of storing memories for extended periods of time, and is where retrieval takes place. On a microscopic scale, the process of forming memories occurs between the neurons of the brain via synapses, which strengthen based on repeated use. Each time a memory is recalled, however, it must be encoded once more, which leads to slight changes in our memories. You may have experienced this over time.
The significance of how our memory works has guided the discovery in improving memory. “Grouping” items, for example, efficiently organizes a large set of information into less, more dense chunks of information, allowing short-term memory to hold more information. Memory “olympists” take this to the extreme with organizing a wide spread of information into more manageable bits.
The process of finding out how memory works and creating models for it also came with exploring unique cases. Henry Molasion, known as the man with no memory, lost his hippocampus in a life saving surgery. Previously, the function of the subsection of the brain was unknown, but it became clear with H.M.’s case that it was involved in encoding memories from STM to LTM. Perhaps most striking was the fact that “muscle memory”, or the body’s ability to hone/remember a certain motor task via repetition, was still maintained; even if H.M. could not remember doing an action, he would get better at it by doing it over and over. This allowed different parts of long term memory to be defined: declarative (facts and experiences) and procedural (playing an instrument, riding a bicycle, motor skills). Memory is an intricate, amazing process, and understanding how it works makes life all the richer.
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