Figure 1.

(A) Computer printouts of superimposed swimming trajectories of a control and of an irradiated rat, trained in light, to find an invisible platform when started from any of the four cardinal points (north, east, south, west) at the circumference of the pool. Control rats headed toward the target, whereas the irradiated rats swam mostly near the wall of the pool (on day 4). By day 10 the irradiated rats covered the entire surface of the pool. (B) Latency to find the platform in irradiated and control rats. The performance of the control rats improved to the asymptote by day 4, whereas that of the irradiated rats remained almost unchanged, suggesting that irradiated animals are unable to learn the task.