The effect of superior colliculus lesions upon the visual fields of cats with cortical ablations

Abstract

The visual fields of 18 cats were measured before and after various lesions. Preoperatively, all cats had identical fields. With both eyes open, they saw from 90° left to 90° right; with one eye, from 90° ipsilateral to 45° contralateral. Thus the field for nasal retina extends from 90° ipsilateral through to the midline; for temporal retina, from the midline through to 45° contralateral In summary, postoperative testing led to two major conclusions. (1) Large occipito‐temporal cortical lesions produce a stable field blindness, but the blindness is alleviated by a transection of the commissure of th superior colliculus (or a unilateral collicular ablation). This transaction yields the same result whether it occurs in an operation before, during, or after the cortical lesion. These data confirm and extend the Sprague effect. (2) Cats made dependent upon retinotectal pathways due to cortical ablations responded much better to stimulatian of nasal retina than to stimulation of temporal retina. This presumably is related to the preponderance of nasal retina as a source of the retinotectal pathway. Since even smaller cortical lesions limited to areas 17, 18, and 19 produce this nasal/temporal retinal difference, it is concluded that integrity of the geniculocorticl pathways is necessary for good temporal retinal vision as determined by these methods.