Math offers new view of brain and its disorders

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Sandy Schaffer

Of the many disorders that can afflict the brain, schizophrenia and autism are among the most inscrutable. The long scientific searches to explain their causes have turned up many clues and inspired various theories. But no clear answers have emerged.

A new way of thinking about these disorders has begun to show promise, Laura Sanders reports. This approach conceptualizes the brain as a fantastic guessing machine that combines information from the senses with expectations based on past experience. Interpreting the external world in this way can be described precisely (and therefore can be tested and explored in a rigorous way) with the use of a mathematical expression known as Bayes’ theorem.

Many scientists now suspect that in schizophrenia, autism and perhaps other disorders, the guesses the brain makes about the external world get derailed — either because of trouble integrating sensory information with expectations, or from failure to adjust expectations based on new information.

Other sorts of problems in the brain have little to do with interpreting reality, but rather reflect the detrimental impact of toxic substances. Lead’s destructive influence in the brain, for instance, is clear and well-documented. Other metals may also pose problems. Sanders explores the current controversy over iron. Iron plays a crucial role in the transport of oxygen in the blood, but too much iron in the brain may be unhealthy; some experts suspect excessive iron contributes to Parkinson’s disease. Others argue that iron starvation is actually the problem for cells in the part of the brain affected by Parkinson’s. That issue has proved difficult to resolve, and researchers are deeply divided — even though clinical trials based on one side of the argument are now under way.

Brain researchers are concerned not only with diseases but also with normal healthy functions, such as sleep. Sanders, Tina Hesman Saey and Sarah Schwartz report several new sleep-related findings: a major role for ion concentrations in the process of awakening or falling asleep; the brain’s strategy for staying alert when sleeping in a strange place; and new evidence from lizards relevant to the evolution of human sleep patterns.

Interest in the brain is not a strictly modern phenomenon. Bruce Bower’s story details new findings about 4,000- to 6,000-year-old skulls in southwestern Russia with rather large holes carved into them. Whether ancient people in this region were trying to peer more closely at the brain, taking part in a religious ritual or attempting some kind of therapeutic surgery is unclear. The scientist who led the team that analyzed the skulls contends that the holes are in the wrong place for a medical intervention and were cut in skulls that were otherwise healthy. Some speculate that the holes might have prepared people for a new, perhaps spiritual role in the group. Apparently, most survived the procedure. While the intent may never be known, those skulls do suggest that people have long been interested in examining the brain to find answers — be they about mental illness, other diseases or even spiritual quests.

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