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Memory and the brain

Forgetting and Amnesia

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“I have it at the tip of my tongue!”

There is no scientific evidence that the various vitamins, minerals, pills, and other supplements that are marketed as boosting your memory actually do so. They may be good for your health, and they are certainly good for the pharmaceutical companies that sell them, but that is all.

Memory is a complex phenomenon that affects many neural circuits in the brain. These circuits are strengthened by various types of neurotransmitters that bind to receptors, like keys that open locks. There have been many studies on substances that can slow the memory loss associated with certain degenerative diseases. But when you introduce an external substance into the delicate balance of your brain’s neurotransmitters, it is more likely to harm your memory than to improve it.

For example, caffeine acts as a stimulant by raising the level of adrenalin in your body. In the short run, caffeine can help you to concentrate. But in the longer run, it can also cause anxiety and insomnia, both of which interfere with your memory.


To excuse their memory lapses, people sometimes cite the saying, “Memory is a faculty that forgets”. But there is really no reason to be ashamed of forgetting things. Forgetting is a natural phenomenon. It is even essential. In fact, the reason we forget is that our brains are organized to eliminate anything that might clutter them up needlessly.

We forget mainly those things that were not encoded firmly enough in our networks of nerve cells. In this respect, forgetting differs from amnesia, which is an excessive memory loss due to a physical injury to the brain or a psychological trauma.

There is no magic pill you can take to improve your memory (see sidebar). But you can improve it in the following two ways.

1) Adopt a healthy lifestyle, and in particular get enough sleep.

Contrary to what you may sometimes hear, you cannot learn new things while you are sleeping (for example, by listening to an audio cassette). But you can more effectively retain the things you learned during the day if you get a full night’s sleep afterward.

Taking sleeping pills, however, will not help your memory, because they reduce the time that you dream, and dreaming is a phase of sleep that is thought to be very important for memorization.

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2) Do things that exercise your memory.

For example, reading is an excellent way of exercising your memory, because it makes you continuously apply your attention and your visual perception, construct mental images, organize information, and do other things that are all essential for a good memory.

Lastly, anything that makes you pay attention and arouses your interest will help you to remember, without your having to mentally repeat or organize the material to be memorized.

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The Persistence of Memory, Salvador Dali (1931)


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Taking Photos To Remember Your Own Life

There is one form of amnesia with which all of us are familiar, because we all experience it every night: the kind that happens when we are asleep! While we are sleeping, many things are going on, not only in our external environment but also in our inner world (for example, when we have dreams or nightmares, or walk or talk in our sleep). However, most of the time, when we wake up, we have no recollection of these activities. We are even so used to this phenomenon that if we cannot recall what happened during some part of the day, we are often inclined to wonder whether we had simply fallen asleep.


Amnesia is a major memory loss, greater than the simple forgetting that occurs normally in everyday life.

Amnesia can affect some areas of memory while leaving others intact. For example, it often erases memories of the recent past while leaving those of the distant past better preserved. Memories of habits (procedural memory) are usually better preserved than memories of facts and events.

Thus, it is rare for anyone to experience total amnesia. Also, people with amnesia often gradually recover their lost memories over time, whether from the time before or from the time after the incident that caused the amnesia.

Amnesia is not so much an illness in itself as a symptom of an injury or disorder in the brain. Amnesias are divided into two major categories according to the type of trauma that caused them: amnesias due to physical brain injuries and amnesias due to psychological causes.

Another kind of amnesia that many of us have experienced is the kind that follows surgery under general anesthesia. For such anesthesia to be considered successful, the patient not only must have no reaction to the operation or to any pain involved in it, but also must not even remember any pain or other events that occurred during it.


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When someone suffers an accident that results in amnesia, the first thing the doctors try to determine is whether the memories lost are of information learned before the accident, or afterward.

If patients can no longer recall events from their lives before the injury, they are said to have retrograde amnesia.


But if they can no longer acquire new memories from the time of the accident onward, then they have anterograde amnesia.

People can have both types of amnesia in varying proportions, with different associated causes. But in all cases, the most distant memories, such as those of childhood, tend to be preserved.

Anterograde amnesia leads to some strange situations. People who have it forget their doctors’ names and, every time they see them, greet them as if they were meeting them for the first time.

These people must use all kinds of strategems to lead an apparently normal life. For example, they may carry around a little notebook in which they write down what they do every day, so that if anyone asks them about it, they can give some kind of an answer. But if, for example, they go to a play and write down its title, when they read it back, they will not have the slightest recollection of whether it was any good.

Various forms of amnesia can selectively affect various types of memory, which can be classified according to their duration or the type of information to be recalled.

Another way of classifying memory is according to whether it concerns things that happened in the past (retrospective memory) or things that you need to remember that are going to happen in the future (prospective memory).

Retrospective memories can be either semantic or episodic. Prospective memories also can be divided into two types: the kind that are triggered by a time cue (for instance: “Remember to go to the doctor’s at 8:00 AM”) and the kind that are triggered by an event cue (for instance, remembering to mail a letter when you are walking past a mailbox). Event cues need not have any direct connection with the thing that you want to remember, as witness the classic example: tying a piece of string around your finger, then associating it with something that you have to do later on.


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