The effect of cortical and tectal lesions on the visual fields of binocularly deprived cats

The visual fields of seven cats raised with binocular lid suture were measured before and after various neural lesions. Each of the cats preoperatively responded with each eye to stimuli from 90 degrees ipsilateral through to the midline. A transection of the optic chiasm rendered one cat blind on the visual field tests. Large bilateral occipito-temporal cortical ablations (4 cats) did not measurably affect orienting responses or the extent of visual field. Unilateral occipito-temporal cortical ablations (2 cats) also had no affect on the visual fields, but subsequent ablations of the contralateral superior colliculus produced permanent blindness in the hemifield contralateral to the ablated tectum. These two cats also were apparently blind with the eye contralateral to the ablated tectum; but with the other eye, the cats retained their preoperative orienting responses. These data are consistent with the hypothesis that, with early binocular deprivation, cats develop dependence upon retinotectal and not thalamocortical pathways for visually guided orienting behavior.