Exponential decay of spatial memory of rats in a radial maze.

The persistence of spatial memory of rats (n = 14) was investigated in an eight-arm radial maze. The animals were trained until the mean number of errors in the first eight choices was 0.2. The decay of performance with time was studied using delays of 5, 20, 60, 120, or 240 min between choices 4 and 5, during which the animal was removed from the apparatus. A delay of 60 min significantly impaired performance. The mean number of errors was not significantly different from the random choice level after a delay of 120 min. The increase in the number of errors with time was exponential. Comparison of the results with those of previous studies suggests that the nature of training may have effects on memory persistence in the radial maze.