In a study of epilepsy patients, the National Institutes of Health found how a series of high-frequency brain waves can help us identify such differences between the past and the present. The study was led by Rafi Haque, a PhD student at the Emory University School of Medicine in Atlanta, who was doing his dissertation with Dr. Zaghloul graduated. His primary research goal was to find out if a theory called predictive coding can be used to help our brains remember past experiences known as episodic memories. To test this idea, the team worked with 14 patients with drug-resistant types of epilepsy whose brains had been surgically implanted with electrode grids as part of a study by the NIH Clinical Center to diagnose and treat their seizures. The experiment began when patients were shown and asked to memorize a series of four natural scenes displayed on a computer screen. For example, one of the scenes was a brown bicycle leaning upright on a stand in front of a green bush.