Consolidation Hypothesis

When, in the normal course of events, can we say that something you noticed is learned? Is an experience immediately stamped in your memory at the instant it occurs? If the "memory matter" is like a tape recorder, recording would be instantaneous. But if the biolog- ical substance is like camera film, it would need to be developed, and the image could be distorted or lost if it were re-exposed be- fore being developed. There is reason to believe that this latter view is closer to the truth. There are a few situations in the laboratory in which an animal can normally learn in a single trial. In one of these a rat is given an electric shock to the paws if it steps off of a small platform; in another, a rat is nauseated by being poisoned shortly after it has eaten a novel food. One experience in such situations is enough for the rat to learn to stay on the platform or to avoid the food. However, if within an hour or so after the initial learning exper- ience, the rat is given electric shock through the brain, it later acts as if the earlier experience has been completely obliterated. Lest you think this phenomenon is peculiar to laboratory rats and electric shock, let me mention two human experiences. One is pre-traumatic amnesia. A person who is involved in an accident that involves some head injury often cannot remember events shortly pre- ceding the accident. The other is the alcoholic black-out. If a person drinks a lot one night, s/he may have no recollection of what happened that night. The term "consolidation" has been given to the presumed process whereby learning experiences become fixed in memory. Although the evidence is not yet conclusive, many psychologists now believe that new learning is initially a very fragile process that is vulnerable to being modified by subsequent events. With the passage of time, and especially with repeated practice, the learning becomes more and more durable. One immediate implication of this hypothesis is that you should try to avoid doing anything that might clutter your mind with contradictory ideas right after a lecture or a study session. Engage in physical or social activities while what you have learned begins to consolidate. One version of this hypothesis proposes that the consolidation process is effected most critically during the dream stage of sleep. I suggested earlier that memory matter may be produced by the brain during dream sleep and perhaps consolidation is a complementary kind of process. In any event, I advise students to spend a few minutes before going to bed in a brief review of that day's lessons. Doing so will refresh those ideas so that they can be fixed in memory when you are sound asleep.

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