It is all right. Everyone does. That is the natural process. Have you noticed the first symptom of getting old? Yes, you guessed it right. You start forgetting things!
Not that you forget everything. You still remember all those nasty things you did in your younger days. Those happy carefree days, those scolding you got from your parents for no fault of yours, and so on. But somehow, you start forgetting where you just left your mobile phone or the spectacles!
Why is it that we remember certain things and tend to forget some others? Do we have different kinds of memory?
Yes, you guessed it right. We do have many types of memories. Some are short term and some are long term and almost indelible.
Let me tell you an interesting episode that helped scientists in understanding how our memories worked.
In 1950s a patient was operated by an American surgeon by name William Scoville as a treatment for his sever epileptic disorder. This patient was Henry Molaison – often referred to as just H.M. for privacy reasons. The surgeon removed some parts of his brain, most notably a structure called Hippocampus.
Post-surgery, H.M. seemed to have almost overcome his epileptic condition. But strangely, he had an onslaught of amnesia! And his memory loss was very strange and he became the target of research for many scientists during 1957 to 2008 till he died.
H.M. was quite a normal person before surgery, except for epileptic seizures. But after surgery, H.M. had severe problem remembering day-to-day events. If he met you the first time, he would talk to you as normal people did. But the moment you turn your back, he would totally forget that he ever met you! You needed to reintroduce yourself once again!
If H.M. was given just four single digit numbers, and if you ask him to recall them after a few minutes, he could not do that. But if you make him repeat the numbers again and again, he could remember them for slightly longer time. But not very long. He would forget all those numbers as well as you, after a few minutes!
But H.M. remembered all the events of his childhood days. However, he had forgotten events that took place a couple of years just before the surgery was done. It was as if the surgery had selectively erased his memory just preceding the event of surgery!
H.M. too, like all normal people, took time to learn this skill. But when he finally learnt the skill, he could draw the star without much problem. But the real problem was that he had forgotten that he was ever trained to do such a task! It is as if he was doing it without any prior training! He knows how to do a task but he does not know that he knows it!
There were other tasks H.M. was tested on. In one such task, he was exposed to many image fragments in a random order. In between, he was also shown images whose fragments he was shown earlier. The task was to recognize the image already familiar to him.
In this task, H.M. performed better than any average person. He could immediately recognize the complete image whose fragments were shown to him earlier. But the irony was that he had forgotten that he had ever seen the fragments before. That means that his brain remembered the fragments though he was not aware of that fact!
All these tests implied that our memories are not one fit for all sizes. But they are of different kinds. We have memories that are long term, short term, medium term and so on.
We also have memories that are explicit such as those that can be recalled explicitly and those that are implicit – the ones that exist but the ones that we cannot voluntarily recall. Like for example the memory related to any physical skill. If someone asks you how you drive a car, you can’t explain, but you can do it by repeating all the steps that are remembered implicitly in your brain, like a stored program in a computer!
Further, all these memories are not stored in one specific place in the brain, but distributed in various regions in the brain. These memories become stronger as time passes if they are used repeatedly and fade out if not used frequently.
So, H.M. was really a great case for scientists to understand one of the important aspects of our mind namely the memory.
We will see more interesting things about our Mind next time.
A series revolving around Mind – Science of Mind, Philosophy of Mind, Notions of reality, Mind modulation, Domains beyond Mind, and so on. © Dr. King 2019
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