Spatial resolution of the Galago.

The spatial vision of two adult galagos (Galago crassicaudatus) was assessed using a two choice discrimination task to determine their contrast sensitivity. Both contrast sensitivity functions exhibited low and high spatial frequency attenuation with the peak sensitivity at 1%. For one animal, the peak occurred at 0.5 c/deg and the extrapolated cutoff frequency was 2.6 c/deg; for the other, the peak was 1 c/deg and the cutoff was 4.3 c/deg. For this animal, grating acuity was also tested and, depending upon definition of threshold, yielded threshold estimates from 4.8 to 6.0 c/deg. The data supports the conclusion that the spatial vision of the galago and the cat is quite similar, a congruence that presumably reflects their adaptation to a nocturnal niche, rather than their divergent phylogenetic origins.