Vernier acuity in the cat: its relation to hyperacuity.

Vernier thresholds were measured behaviourally in five cats using offsets in gratings of two spatial frequencies and in single lines. Thresholds ranged from 2.2 to 6.7', and no threshold differences were found across stimuli. These results are discussed in relationships with published spatial resolution data and are related to the optical and neural characteristics of the cat's visual system. It is concluded that if vernier acuity is a hyperacuity in cats, the improvement in grain is not of the same magnitude as it is in humans.