Currently, the method used to avoid severing nerves and causing neurological brain damage during such medical procedures involves asking the patient to perform certain tasks while electrically stimulating parts of the brain bordering where the surgeon plans to cut. The electrical stimulation inhibits brain function in that region, revealing whether losing that tissue would cause permanent damage. The process is effective, albeit slow.

Now Paul Hoy and his colleagues at the University of Southampton are developing a rapid and highly sensitive method for measuring brain function across the entire area during surgery. They said their method is based on observing blood flow in the brain. Active brain regions have increased blood flow, and this change can be observed by looking at light reflected off the brain because hemoglobin absorbs light differently, depending on whether it carries oxygen.

The research will be presented Oct. 21 in Rochester, N.Y., during the annual joint meeting of the Optical Society of America and the American Physical Society's Division of Laser Science.