The visual aura some people experience with migraine headaches is caused by “spreading depression,” a wave that begins in the outer portion of the brain and spreads throughout the gray matter. During the wave, nerve cell activity lessens and brain tissue swells. A similar wave, called ischemic depolarization (ID), occurs during a stroke. Ischemic strokes cause the sudden death of brain cells when blood flow to the brain is blocked. Although spreading depression was first reported more than 60 years ago, researchers are still unclear about how the wave is generated. Ning Zhou is using a new imaging technique, called two-photon laser scanning microscopy, to examine detailed changes in individual cells when brain tissue suffers from spreading depression or ischemia (insufficient blood supply). Although these two events are similar, brain cells do not die during the wave of spreading depression. Zhou will examine the differences to discover why nerve cells undergo unusual swelling during spreading depression, and how this contributes to cell death during stroke. This research could provide insight into how to prevent tissue damage induced by strokes.