It might take only the touch of peach fuzz to make an autistic child howl in pain. The odour of the fruit could be so overpowering that he gags. For reasons that are not well understood, people with autism do not integrate all of their senses in ways that help them understand properly what they are experiencing. By the age of three, the signs of autism—infrequent eye contact, over-sensitivity or over—sensitivity to the environment, difficulty mixing with others—are in full force. There is no cure; intense behavioural therapies serve only to lessen the symptoms. The origins of autism are obscure. But a paper in Brain, a specialist journal, casts some light. A team headed by Marcel Just, of Carnegie Mellon University, and Nancy Minshew, of the University of Pittsburgh, has found evidence of how the brains of people with autism function differently from those without the disorder. Using a brain-scanning technique called functional magnetic-resonance imaging (FMRI), Dr. Just, Dr. Minshew and their team compared the brain activity of young adults who had "high-functioning" autism (in which an autiat"s IQ score is normal) with that of non-autistic participants. The experiment was designed to examine two regions of the brain known to be associated with language—Broca"s area and Wernicke"s area—when the participants were reading. Three differences emerged. First, Wernicke"s area, the part responsible for understanding individual words, was more active in autists than non-autists. Second, Broca"s area—where the components of language are integrated to produce meaning—was less active. Third, the activity of the two areas was less synchronised. This research has led Dr. Just to offer an explanation for autism. He calls it "underconnectivity theory". It depends on h recent body of work which suggests that the brain"s white matter (the wiring that connects the main bodies of the nerve cells, or grey matter, together) is less dense and less abundant in the brain of an autistic person than in that of a non-autist. Dr. Just suggests that abnormal white matter causes the grey matter to adapt to the resulting lack of communication. This hones some regions to levels of superior ability, while others fall by the wayside. The team chose to examine Broca"s and Wernicke"s areas because language-based experiments are easy to conduct. But if the underconnectivity theory applies to the rest of the brain, too, it would be less of a mystery why some people with autism are hypersensitive to their environments, and others are able to do certain tasks, such as arithmetic, so well. And if it is true that underconnectivity is indeed the main problem, then treatments might be developed to stimulate the growth of the white-matter wiring.