Perception of visual motion coherence by rats and mice.

The coherence thresholds to discriminate the direction of motion in random-dot kinematograms were measured in rats and mice. Performance was best in the rats when dot displacement from frame-to-frame was about 2 degrees, and frame duration was less than 100 ms. Mice had coherence thresholds similar to those of rats when tested at the same step size and frame duration. Although the lowest thresholds in the rats and mice occasionally reached human levels, average rodent values ( approximately 25%) were 2-3 times higher than those of humans. These data indicate that the rodent and primate visual systems are similar in that both have local motion detectors and a system for extracting global motion from a noisy signal.