Laughter? It's all in the head

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RECENTLY AN unpredictable event during a routine brain operation caught everyone's attention. A neurosurgeon in the States was operating on a patient with severe epilepsy. In accordance with established procedure, he was stimulating parts of her brain while she was conscious in order to be sure how the brain region being treated was associated with certain functions. Ghoulish though it may sound, it is in fact painless, simply because there are no "receptors" for pain in the brain. Indeed, the strategy of exploring the brain has been conducted since the middle of this century.

One of the pioneers in the field was a Canadian neurosurgeon, Wilder Penfield. Penfield found that stimulating certain regions on the surface of the brain would sometimes trigger a memory in patients. This work has been seized upon, understandably, by those probing the miracle of how a brain can remember complex episodes. Worth noting is that frequently the patient claimed a certain sensation along with the narrative - that they felt as though they were in a dream. The stimulation had generated a concomitant feeling.

Another type of feeling was inferred in a separ- ate investigation where a deeper region of the brain was stimulated. This work, originally performed on rats in the 1950s, found that the animals would press a bar to stimulate certain parts of their brain electrically. The sites for this "self stimulation" were dubbed "pleasure sites", since it was inferred that a rat would only work at pressing a bar if some sort of pleasure was being experienced. I remember seeing a film made during that era, a patient had an electrode implanted in a comparable region of her brain, she described the effects of stimulation as giving a direct sensation of feeling good.

Which brings me to the recent discovery on the Californian operating table. When a certain part of the patient's brain was stimulated she laughed. This was no mere reflex, no neurosurgical tickle, where one's face is in a rictus of muscle-aching, mouth-stretching, but inside one is in agony. No, this was genuine mirth where anything the patient was shown during the stimulation was perceived as funny. Had the neurosurgeon stumbled on the "centre" for laughing? Almost certainly not. Tempting though it is to view the brain as working as a series of autonomous centres. We now know that different brain regions contribute to "net" functions such as memory, vision and language, like instruments in an orchestra. The trick is to find exactly what the contribution is and how the structures work together, indeed it is currently one of the biggest challenges in neuroscience.

Instead of interpreting the finding as activation of an independent centre, it could be that the stimulation initiates the triggering of a cascade of reactions in different parts of the brain. Perhaps more thought-provoking still is that when the brain is configured in this yet-to-be-identified fashion previously unfunny scenarios are perceived as mirthful. Clearly, our previous ideas that sense of humour is invariant and/or develops slowly with a particular culture and mind-set, have to be revised. Accounts of what is funny usually focus on the qualities of the particular event or person, the unpredictability and so forth. Now we have the chance to tackle the question from the other side, and ask what is re-configured in the brain to modify our subjective reaction so transiently and so rapidly. The science of laughter has for too long been the poor relation of brain research: and yet, the therapeutic effects of humour are being increasingly acknowledged. Perhaps that chance neurosurgical observation will prompt brain researchers, at last, to take humour seriously.