Short-Term Memory

Neuroscientist Neil Burgess on the difference between short-term and long-term memory, phonological loop, and amnesic people

videos | May 25, 2018

Part of the reason for distinguishing short-term memory or working memory from long-term memory came from the 1950s, when people began to understand the nature of how memory depended on the brain. When Brenda Milner made her discovery with William Scoville that memory, being able to remember what had happened in the past essentially in terms of personal experience, was really strongly dependent on the hippocampus. When she studied a patient, who had had bilateral hippocampal removal, in the service of securing his epilepsy, she noticed that he was amnesic, he couldn’t remember what had happened to him in the past.

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Interestingly, in subsequent experiments by her and other colleagues it was realized that there were many areas of preservation of memory in this kind of amnesic patient. Indeed he could remember semantic facts about the world, he found it difficult to learn new ones. He could remember the ones he already knew, he could learn new tasks like riding a bicycle, though that wasn’t the one they taught him. They taught him to do some tracing of shapes when looking in the mirror and this kind of things. He was able to do that kind of learning. Also his short-term memory seemed to be fine. So, it seems that this sort of short-term memory is different to the general memory or long-term memory where he can’t remember what happened to him in the days and weeks.

What we’ve learned from this is that there are probably neocortical mechanisms, parts of the brain outside of the hippocampus, which can support for a very short time certain kinds of information like a sequence of numbers or a sequence of locations, or a sequence of actions.

The distinction between short-term memory and long-term memory as originally made as: “Here’s a box that involves hippocampal system, in which we put our long-term memories for long-term storage and then here’s another box, which is somewhere else in the brain, perhaps in parietal and prefrontal areas, which we can store things for a short period of time”, that story is becoming a little bit more mixed now.

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The classic distinction between short-term memory and long-term memory really was a distinction between things that you can keep online if I present this information and you can continue to think about it and then you’re tested on what had happened.

What we get is a picture, where different kinds of things are actually remembered in in slightly different ways. There seems to be some commonality in that. If you have to remember something for a long time, and if you’re going to be asked a long time later, which is no hope that you could keep this information active for that time, then you probably will depend on the hippocampal memory system. Amnesics won’t be able to remember that information, if it’s stuff that you have to actually remember the experience of seeing before. Whereas the actual mechanisms used for short periods of time or long periods of times may differ. They may depend on different parts of the brain, that may depend on the nature of the information that you’re trying to remember.

Professor of Cognitive and Computational Neuroscience, University College London
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