It's not much different from short-term memory, it's just that the location of storage is primarily in the cortex for the long term and the hippocampus for the short term. It's all about specific connections between neurons and neurons that determine what is stored. What is the carrier that stores it for so long? Neuron to neuron specific connections, you could argue that it's mainly in the cerebral cortex. Doesn't it disappear with cell turnover? You could argue that brain cells in the cerebral cortex don't turnover. But memories of long ago, memories that have not been activated for a long time, have weakened connection strengths that make you less likely to think about them, and if there were fewer memories in the cortex in the first place, and they've been immobilized for a long time, they may be gone, or the number of them may not be sufficiently small to allow you to think that you experienced it, received it, and so on.

Dan Gilbert, in The Stumbling Happiness, suggests an explanation: the brain selectively remembers key information in a very small number of snippets, and then uses the rules it already knows and the current state of affairs to "brainwash" the memories back into existence.

For example, if you ask someone who just graduated from college what you were doing on June 13th, five years ago, the brain first queries the memory to see if there were any "special events" on that day -- for example, if you went out to an unforgettable birthday party that day. If there was, then you can make up a memory based on this memory. If so, according to this memory, brainstorming to participate in the birthday party have birthday classmates personally, their hardcore Zhang San Li Si, and so on, and then further brainstorming the usual birthday party program: such as dinner, blowing out candles, cutting the cake, playing poker, and so on.

If there is no memory of the special event, then automatically according to the rules "end of June and early July for the final exams" "I am a good student to study well" and so on brainstorming: I was preparing for the exams, the evening in the paper, sitting in my own home, sitting in my seat, with a good student at hand. I was preparing for my exams, working on my papers at night, sitting in my own seat in my house, with the cup I used to drink tea in at hand, and so on. This process of brainstorming is easily disturbed by the current situation. For example, if you ate boiled fish today, you are more likely to "remember" that you ate boiled fish on your birthday; similarly, if someone asks you, "What did Wang Wu wear at the party that day? If someone asks you, "What did Wang Wu wear at the party?", you are more likely to "remember" that Wang Wu went to the birthday party and make up the dress and behavior of Wang Wu according to your understanding of Wang Wu on that day (while in reality, Wang Wu might not have gone to the party at all). Therefore, the so-called "long-term memory", except for a few impressive, the other is basically your own movie based on some basic principles.