Grating acuity of the golden hamster. The effects of stimulus orientation and luminance.

Twelve golden hamsters learned visual discriminations in a Y-maze for a food reward. After initial training on a light/dark task, the hamsters learned to discriminate a grating from a uniform grey field of the same mean luminance as the grating; grating orientation was varied among hamsters. Those animals trained with the grating vertical or horizontal learned significantly faster than those trained on obliques. Acuity, measured by varying the spatial frequency of the grating according to the descending method of limits or the method of constant stimuli, was determined to be about 0.7 c/deg at 50% correct or 0.5 c/deg at 70% correct for all orientations tested (0 degrees, 45 degrees, 90 degrees, 135 degrees). Acuity was relatively constant within the human photopic range, but decreased to about 0.35 c/deg at 5 x 10(-4)cd/m2. The change in acuity as a function of luminance suggests that the hamster has a rod-dominated retina.