A study by Stanford University School of Medicine investigators may help explain why even people benefiting from medications for their epilepsy often continue to experience bouts of difficulty thinking, perceiving and remembering clearly.

The cause is a pathological buzz of electrical brain activity that interferes with the brain’s normal activity. The researchers said that certain medications or implantable devices could be improved to alleviate these cognitive deficits.

A paper describing the findings will be published October 16 in Science Translational Medicine.

The electrical interference has important behavioral consequences. To examine them, the researchers tested the ability of six patients, who had sensors implanted in their brains, to solve certain kinds of problems during periods when a buzz of electrical activity was colliding with their brains’ normal responses.

This pathological buzz, called a high-frequency oscillation, or HFO, is associated with the onset of epileptic seizures. HFOs can be undetectable to the naked eye—even the trained eye of a neurologist, said Josef Parvizi, MD, Ph.D., professor of neurology and neurological sciences and director of Stanford’s Program for Intractable Epilepsy.