by Nigel J.T. Thomas©
First published on this site, April 4th, 2011.
Not long ago, I received an email from a man who had been trying to get his seven-year-old son interested in science, and teach him a little bit about the workings of the brain. He had been showing his son one of those diagrams of a brain with various regions labeled as "speech center," vision center," and the like (something similar to this, I suppose), when the little boy suddenly asked, "Daddy, which part of the brain does imagination come from?". It was not on the diagram, and the father, although he studied human biology at college, realized he did not know the answer. As we do these days, he got on the internet to try to find out. It was not as easy as he might have expected. "Imagination" is certainly a word that is found on a lot of web pages, and there are plenty that seem to be devoted to celebrating or promoting it, but very few of them seem to have anything at all to say about what it is, how it works, or where in the brain it might be implemented. Eventually, he found his way to this site. Even here, however, he could find no straightforward answer to his son's apparently straightforward question. (The truth is, the question is not nearly as straightforward as it appears.) He thought I might be a good a person to ask, however, and sent me an email. What follows is a lightly revised version of the reply I sent. It is not written in terms that a seven-year-old could understand (I am not clever enough to do that), but neither is it pitched at the professional, academic level of most of the material on this site. I would like to think that it answers the question (inasmuch as it can be answered in the current state of scientific knowledge) in a way that a layperson should be able to understand, and that they might then be able to explain to a curious and intelligent child. If you want to know the detailed reasons, and see the citations to the scientific literature, that justify the claims made here, you can find them in the other articles on this site. - N.J.T.T.
Many parts of the brain (perhaps, even, most parts) are involved in imagination. Partly this is true because there are so many types and aspects of imagination. Imagining, for instance, what President Obama would look like if he had a long beard, is something very different from imagining what it would be like to be able to fly like Superman, or imagining (as part of a game) that you are a detective, or imagining that you have $15 in your pocket (when you really only have $5 there).
But I also think that even if we narrowed the question down to just one sort of imagination it would still be true that many parts of the brain are involved in it, although some parts may be doing more of the work of imagining than others. Unfortunately, although we have some ideas about it, scientists do not yet really know for sure which those parts are. Probably a lot of the work of most sorts of imagining are done by the same parts of the brain that are responsible for perception, but that is already an awful lot of the brain.
Also, I should say that parts of your body outside your brain are probably involved in imagination as well. Experiments have found that when people visually imagine something, their eyes move in the same sort of way that they would move if they were actually looking at what they are imagining. (Our eyes move a lot when we are actually looking at things, even though we are mostly not aware of it.) For instance, if you imagine a skyscraper, your eyes tend to move up and down, as if you were looking at it from top to bottom, and if you imagine a train, your eyes tend to move from side to side as though looking along it (and if you are prevented from moving your eyes in these way, you will probably not be able to get a good mental image). Also, if you imagine, for instance, lifting a heavy weight, there will be electrical activity in the muscles in your arm, even though your arm does not actually move. Probably, the activity in the muscles (and the signals the muscles send back to the brain) is just as much a part of the imagining as is the activity in the brain that signaled the muscles to move, but then told them not to move after all.
The occipital cortex (also called the visual cortex), at the back of the head, is one of the first places in the brain where information coming in from our eyes arrives, and where a lot of the work of understanding what we are seeing goes on (although many other parts of the brain are also necessary for us to be able to see normally). In some experiments with brain scanners scientists have found that when people are using their visual imagination (having mental imagery, "seeing" things in their mind's eye), this part of the brain works particularly hard. Because of this, some scientists think that the occipital cortex is where most of the work of visual imagination goes on.
However, I myself very much doubt that things are so simple. For one thing, there are other brain scanning experiments do not show the occipital cortex working particularly hard when people are using their visual imagination, but show other parts working harder instead (it might depend on exactly what they are trying to do with their mental imagery). Also, there are people whose occipital cortex has been badly damaged by sickness or in some other way. (I know of one woman who lost most of her visual cortex when she was struck by lightning on the back of her head.) This makes them blind, or partly blind (depending on how much visual cortex is destroyed), but most of them are still able to see things in their mind's eye quite well. Indeed, they sometimes have vivid hallucinations, as if their visual imagination is stronger than ever, but is partly out of their control.
So, I am sorry that there is no straightforward answer to your question, partly because imagination itself is so various, partly because most sorts of imagination probably involve very many parts of the brain (and other parts of the body too), and partly because there is a lot we still have to find out about it. Perhaps the best short answer is, imagination does so much, that it uses all of your brain, and other parts of you too.
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