Human memories are formed through the workings of the nervous system, and how long they last depends on repetitive stimuli and changes in synapses. Short-term memories are chemical changes, but when they are converted into long-term memories through repetition, structural changes occur in the nerve cells that make them last longer.
They say that humans are animals of forgetfulness. Some memories are so deeply embedded in someone’s mind that they never fade, while others fade away after just a few hours. This is something we can easily see in our daily lives. For example, you may have memorized something right up until the last minute before an exam, but it disappears from your mind as soon as you get the exam paper, or you may have a trivial memory from years ago that pops up out of nowhere. Memory is unpredictable and variable, and this characteristic has a huge impact on all aspects of human life.
We can learn because we can remember, and we can be human because we can learn. Memory and learning are inextricably linked, and they have a lot to do with our survival. For example, the ability to remember certain dangers or the skills we need to survive is an important tool for keeping our lives safe. If you ask people to think specifically about what it’s like to remember, they’ll realize that it’s not an easy task. Someone with a literary imagination might think of a drawer in their head, while someone else might think of their brain. But beyond that, most of us will be limited in our understanding of the specific mechanisms of memory.
So what is it that allows humans to remember things, and why do memories vary in shelf life? To understand this question, we first need to look at the anatomy of the brain and nervous system. Before we dive into the mechanisms of learning and memory, it’s worth recalling some simple biology facts from high school. We can all agree that memories are stored in the brain. Since the brain is part of our central nervous system, we need to know about the “nervous system”. The nervous system is the system in the body that is responsible for receiving internal and external stimuli, transmitting signals, making judgments, and reacting to them. In this process, memory works by processing and storing information through the nervous system.
The structural and functional unit cells that make up the nervous system are called “neurons,” and you could say that signals travel on roads called neurons. At the front of the neuron is the neuronal cell body, which is involved in the metabolism of the neuron; the neuronal cell body sprouted branches that receive signals; and at the back of the neuron are axons that extend out like a tail. This structure allows signals to travel quickly and efficiently, and as a result, humans are able to remember and store a wide variety of information.
Signals about a stimulus travel in a cascade, from one neuron to the next. Within a neuron, electrical signals travel due to differences in the concentration of ions inside and outside the neuron, but it is the transmission from neuron to neuron that is of interest here. The gap between the axon of the preceding neuron (the presynaptic neuron) and the branches of the following neuron (the postsynaptic neuron) is called a synapse. The transmission process at the synapse is one of the key mechanisms for memory formation, and if it is not efficient, memories can quickly disappear or become distorted.
The scientist who uncovered the mechanisms of memory is Eric Richard Kandel, who was awarded the Nobel Prize in Physiology or Medicine for his work. His research showed that memory involves more than just storing information. Kandel used an animal with a simple neural circuit called the sea hare as a test subject to analyze the molecular biology of memory formation. The experiment clearly showed the difference between short-term and long-term memory retention. From this, Kandel realized that learning and memory can be strengthened through simple repetitive training.
To summarize, short-term memory is a functional change involving the release of chemicals, while long-term memory is an anatomical change in which the shape of the cell itself changes. We can also see that in order for a short-term memory to become a long-term memory, the same stimulus must be repeated, just like the sea hare’s tail was stimulated many times. In other words, “repetition” has been scientifically proven to work. When we learn something repeatedly, the information is stored in long-term memory and retained for a long time. This explains why repetition is so important when studying for a test or learning a foreign language.
Given that long-term memory strengthens the number and structure of synapses, you can now imagine an increasingly complex network of neurons when you think of remembering. Like a tree with expanding branches, our memories are constantly growing and changing with repetition and stimulation. As such, memory is not just a process of information storage, but an important phenomenon that shows how our experiences and knowledge evolve and strengthen over time.
