Cardiac arrest can take a particularly harsh toll on the hippocampus, the area of the brain that plays a role in memory and navigation. A lack of oxygen during a severe attack one where the victim stops breathing can either kill or seriously damage neurons, the primary cells of the nervous system.

The neurons that do survive a heart attack may undergo major structural changes that can affect learning, memory and other behaviors, said Courtney DeVries, the study's lead author and an assistant professor of psychology and neuroscience at Ohio State University.

Indeed, in the current study the mice that had had a heart attack had far more difficulty learning a new spatial task than did healthy mice.

"The neurons that survived a heart attack looked very different from normal, healthy neurons," DeVries said. "These changes could be part of the physiological basis for memory deficits and other behavioral changes that patients often report following an attack."

The study appears in a recent issue of the European Journal of Neuroscience.

Mice were put into two groups one group underwent surgically induced heart attacks, while the other group, the control group, underwent the same surgical procedure minus the attack. Mice in the heart attack group spent about eight minutes in cardiac arrest enough time to stop the flow of oxygen to the brain.

Prior to surgery, the animals navigated the Morris water maze a task that requires finding an escape platform hidden just below the surface of opaque water. Mice underwent three trials a day for eight days to acclimate them to the maze. Each mouse had 60 seconds to swim around the circular, two-meter-wide tank to find the platform. The researchers tracked how long it took each mouse to reach the platform, as well as how fast and how many meters the animal swam during its search.

By the end of this training phase, each mouse had learned where the platfor
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Contact: Courtney DeVries
devries.14@osu.edu
614-538-9529
Ohio State University
29-Sep-2004

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