Simple mathematical computations underlie brain circuits

The brain has billions of neurons, arranged in complex circuits that allow us to perceive the world, control our movements and make decisions. Deciphering those circuits is critical to understanding how the brain works and what goes wrong in neurological disorders.

MIT neuroscientists have now taken a major step toward that goal. In a new paper appearing in the 9 August issue of Nature, they report that two major classes of brain cells repress neural activity in specific mathematical ways: One type subtracts from overall activation, while the other divides it.

''These are very simple but profound computations,'' says Mriganka Sur, the Paul E Newton Professor of Neuroscience and senior author of the Naturepaper. ''The major challenge for neuroscience is to conceptualize massive amounts of data into a framework that can be put into the language of computation. It had been a mystery how these different cell types achieve that.''

The findings could help scientists learn more about diseases thought to be caused by imbalances in brain inhibition and excitation, including autism, schizophrenia and bipolar disorder.

Lead authors of the paper are grad student Caroline Runyan and postdoc Nathan Wilson. Forea Wang '11, who contributed to the work as an MIT undergraduate, is also an author of the paper.

A fine balance