Believe it or not, we have different kinds of memory systems in the brain. In this post, I am going to cover three of them: episodic, procedural and working memory. All of them serve for a different purpose, and research shows that they are independent. It's perfectly possible to forget how your life has been so far and still remember how to play a piano. 😮
Episodic memory stores the events in our lives, and it is divided into two different memory systems: retrospective and prospective memory.
You probably remember what you had for breakfast or the first day of school when you went to the first grade. All these are episodic memories. We remember how our life has been thus far. A common misconception is that our memories are like a film, an accurate description that can be rewound like a video on YouTube. Not at all!
What we remember are just some key things that our brains can use to reconstruct what happened into a cohesive representation. We can only remember the things we paid attention to and we are more likely to remember accurately anything that is out of the ordinary, because it catches our attention and is worthy to be stored in the brain. Anything normal can be omitted because it can be reconstructed from common world knowledge when we recall what happened in the past. For example, your brain doesn't necessarily need to remember that the hotel room you were in 10 years ago had a door and a bed, because that's what hotel rooms typically have. But you would clearly remember if one of these things was missing, though! 😂
This makes our retrospective memory fragile. And it has been demonstrated many times that memories can be altered and implanted. Just by changing a minor detail. One study showed that the most of the people who witnessed a crime remembered the thief wearing a red hat when a scientist pretending to be one of the test subjects gave such a testimony. Even though, in reality the thief was not wearing a hat at all. So fragile is our memory. 😲
How many times have you forgotten to buy milk even though it was the main reason you decided to do groceries? Remembering things to do and appointments in the future is a what is known as prospective memory. It is part of the episodic memory, because it too is about events in life, although those that haven't yet taken place.
Skills such as knowing how to play an instrument or how to eat with a fork and knife are part of the procedural memory. Curiously, people who have amnesia and can't even remember who they are, don't have any problems in remembering how to use their skills.
Even new procedural memories can be formed when no more episodic memories can be formed. This has been studied with people who have suffered a brain injury on their hippocampus, the area in the brain that is needed for new episodic memories to be born. A doctor was wearing an electric buzzer that would give a shock to whoever shook hands with him. He would introduce himself everyday to his patient, who swore he had never met him before. However, over time the patient who still didn't remember ever seeing the doctor started to refuse to shake his hand. He couldn't give a reason why, but he just stated that he has a bad feeling about shaking hands with the doctor. So the patient had developed a new procedural memory even though he couldn't form any new episodic memories.
We have a skill to remember things for a short time. These memories might never get to the level of becoming permanent, but we need them to complete every-day tasks. We have to be able to remember where we are, what is around us, what was said before in the conversation we were having and so on.
There's a hypothesis that the working memory consists of a phonetic loop, episodic buffer, visuo-spatial sketchpad and central executive. The phonetic loop is needed for remembering what was said before. The episodic buffer can be used to store current events and recall past events. The visuo-spatial sketchpad links what we see to how we understand the environment around us. For example, we don't have to turn our heads to somewhat know what is behind us. The central executive is the part that keeps the entire working memory system up and running.
Still much is unknown about how our memories are formed and what is the real amount of different memory systems. This is just something we have to stay tuned for when the cognitive science develops. 😅