Behavioral correlates of 'tectal compression' in goldfish. II. Visual acuity.

Visual acuity was measured in three normal goldfish and two goldfish in which the caudal optic tectum had been ablated bilaterally. Compression of the retinotectal map was assumed to have occurred in the two operated fish, which were tested more than 200 days after surgery. The results indicated that the visual acuity of the normal fish ranged from 0.94 to 0.95 degrees of visual angle. The visual acuity of the fish with presumed compression of their retinotectal maps ranged from 1.91 to 2.07 degrees. The results suggest that compression of the retinotectal map occurs at the expense of the spatial-resolution ability of the visual system.