The curious effect of flying pigs

If a flying pig flapped into your peripheral field of vision right this minute, certain bits of your brain would start firing off electrical charges like crazy. One of them, an area in the parietal lobe, slightly back from and to the side of your crown, would divert your attention from this article to the pig-inhabited airspace; neighbouring cerebral areas would swivel your eyes and direct your hearing towards it.

If a flying pig flapped into your peripheral field of vision right this minute, certain bits of your brain would start firing off electrical charges like crazy. One of them, an area in the parietal lobe, slightly back from and to the side of your crown, would divert your attention from this article to the pig-inhabited airspace; neighbouring cerebral areas would swivel your eyes and direct your hearing towards it.

Meanwhile, deep in your limbic system, a nugget of tissue called the amygdala would trigger the physical changes needed to fight, flee or set off in pursuit. Those various brain activations would occur, too, if you saw something familiar but frightening - an aggressive neighbour spoiling for a fight; a snarling dog. Such responses are designed to help us to deal with potentially dangerous or challenging circumstances without having to do a lot of time-consuming thinking. You do not have to be conscious of the stimuli for the responses to occur.

In the case of the flying pig, an additional area would also become active. It is a spot in the dorsolateral (upper side of the) prefrontal cortex (DLPC), the chunk of brain behind your forehead. Experiments using the laboratory equivalent of flying pigs - "impossible" geometric figures, for example, or human faces with their features jumbled up - show that in normal subjects the DLPC remains lit up for much longer when the stimulus is novel than when it is merely unexpected or emotionally charged.

That suggests that one function of that bit of brain is to hold and focus attention on new things, presumably in order to extract from them as much information as possible and thus as many clues as we can about how best to deal with them. It is tempting to go one step further and assume that damage to the DLPC - from stroke or head injury - would disrupt our ability to deal with new things, and that people who are uninterested in novelty or unable to lock on to new things for long enough to learn from them may be dysfunctional in the DLPC area.

One must be careful about making such leaps from theory to practice. There is a cautionary, if apocryphal, tale of a learned professor who claimed that frogs hear with their legs and demonstrated it by teaching a frog to jump on command, then chopping off its legs and showing that it no longer heeded his word. Similarly, proving that a particular bit of brain lights up when we do something is not the same as proving that the thing in question is actually done by that bit of brain.

In the case of DLPC damage, there does seem to be a clear connection between laboratory experiment and real-life behaviour. People who have strokes in the frontal parts of the brain do not usually suffer the obvious handicaps - speech and movement problems, for example - that afflict those whose strokes are in other areas. But people close to them often report subtle changes of personality.

One of the most common observations is that such people become uncharacteristically apathetic, lose curiosity and show interest only in familiar topics. A team of US neurologists has linked such behaviour specifically to DLPC damage. Researchers from Harvard and Northwestern University Medical School, in Chicago, showed a series of pictures to two groups, one of patients who had suffered stroke damage to the DLPC; the other of normal controls. Some of the pictures showed an unchanging and unremarkable background scene; others showed some sort of visual novelty that the subjects were unlikely to have come across before.

The groups were allowed to view each picture for as long as they liked, and the time spent looking at each one was monitored. The results showed that both groups were initially captured by the novel images, but after a short while their behaviour started to differ. The normal controls spent much longer looking at the novelties, while the stroke patients divided their attention equally between those and the familiar background scenes. Their behaviour in the laboratory mirrored their behaviour outside it: they seemed to have lost the ability, or desire, to explore or to learn new things.

Pinning a particular behaviour to a precise piece of brain tissue is hugely satisfying for brain researchers, who are racing to create a detailed map of brain functions, a similar task to mapping the human genome. But it is of more than academic importance, because once a function has been localised, it becomes possible in principle to manipulate it, just as knowing which gene does what allows geneticists to engineer DNA.

The brain is extraordinarily sensitive, and it takes only a tiny prod from an electrode - or even a pulse from a magnet on the skull - to spark an area into life or to damp its activity down. Direct brain manipulation of such a kind is already being used to relieve the symptoms of obsessive-compulsive disorder, and people with Parkinson's disease are sometimes treated by having tiny electrical implants placed deep in their brains to stimulate activity in the neurones that control tremor. Manipulation of that sort may bring about a permanent change in the brain by stimulating regrowth of local tissue.

So far, such techniques have been limited to use in cases where a very specific brain disorder is apparent, but there is no reason it should not also be used to adjust subtler personality "deficiencies" once the brain mechanisms responsible for them have been localised. Apathy caused by DLPC dysfunction may be one of the first such deficiencies to lend itself to that sort of treatment, and stroke patients are not the only people who may be suitable for treatment.

A loss of interest in novelty is one of the central features of depression, and if DLPC dysfunction could be corrected in that regard, many of its worst symptoms might be alleviated. Apathy is one of the core negative symptoms of schizophrenia, too, and is seen in its most extreme form in catatonia. It may also be one of the underlying causes of attention deficit disorder (ADD), which is characterised by the inability to remain focused on anything.

ADD is usually associated with hyperactivity, which seems at first sight to be quite the opposite of apathy. But there is another type of ADD, in which the sufferer (usually a child) seems dreamy and unengaged, much like stroke patients with DLPC damage. If stimulating the DLPC is found to help people with depression, stroke-induced apathy and ADD, what will it do for normal people?

The ability to lock on to new things is obviously advantageous - it is another way of describing curiosity, and curiosity prompts us to learn. But curiosity is limited in most of us. Given a new puzzle, we may spend more time on it than on one we have already solved, but if it is too difficult, we get bored or distracted and give up.

If DLPC activity could be enhanced, the chances are that we would focus more closely on the new challenge and worry away at it until we had cracked it. That is precisely the behaviour that characterises successful entrepreneurs, and it is becoming more and more useful, as our need to master new skills increases. Direct brain manipulation for personality enhancement may not be available yet, but it almost certainly will be one day.

You can already buy devices that claim to send magnetic charges through the skull to perk up the tissue beneath. They are unlikely to be effective, because the magnetic field is diffused through the skull and does not therefore actually reach the part where it is needed. But technology will no doubt improve. One day we may all have the capability to stimulate precise spots in our frontal lobes and become uncharacteristically obsessed with the latest computer game.

For the moment, you can stimulate your DLPC by seeking out new and challenging situations and things such as puzzles, games and unusual works of art. Introduce a few flying pigs into your life - you will feel the benefit.

Rita Carter is the author of 'Mapping the Mind' (Seven Dials, £14.99)