They simulated the hyperexcitation of neurons in a portion of the brain and found that the stimulus produced traveling waves of electrical activity.

To test the accuracy of their model, the UC Berkeley researchers teamed up with Dr. Heidi Kirsch, assistant professor of neurology at UC San Francisco's Epilepsy Center. Kirsch was treating a 49-year-old epilepsy patient whose seizures were not reliably controlled by medication. The patient was diagnosed with mesial temporal sclerosis, a condition in which the hippocampus, the part of the brain that organizes memories, is smaller than normal.

"We estimate that two-thirds of patients with epilepsy will respond to medication," said Kirsch, who also co-authored the paper. "For a number of the remaining one-third of patients, surgical removal of the part of the brain where seizures begin may offer a cure. The goal in seizure surgery is to find one spot where the seizure comes from, and when taking it out, to not hurt the patient."

Before surgery, neurologists needed to map the region where the patient's seizure originated to ensure that they only remove what is necessary. To help neurologists observe the patient's seizures, 64 electrodes were implanted into his brain for a week. The researchers were thus able to obtain data from six of the patient's seizures to compare with the mathematical model they had created.

The researchers focused on two subdural electrodes spaced a centimeter apart on the surface of the patient's brain. They noticed a consistent delay of 25 milliseconds in electrical peaks between the two electrodes, indicating a strong, coherent wave pattern characteristic of a seizure.

"The wave signals from both the model and the observational data were similar in shape, frequency and speed of propagation
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Contact: Sarah Yang
scyang@berkeley.edu
510-643-7741
University of California - Berkeley
23-Feb-2005