Visual discriminations of cats with cortical and tectal lesions.

Fourteen cats were trained on three visual discrimination tasks: light vs. dark, horizontal vs. vertical stripes, and upright vs. inverted triangles. Four of the cats then underwent large, bilateral occipito-temporal cortex ablations; postoperatively, they demonstrated little or no visually guided orienting behavior and solve only the brightness task and not the preoperatively learned pattern discriminations. Six other cats underwent the same cortical ablations plus a transection of the commissure of the superior colliculus; postoperatively, they demonstrated good visually guided orienting behavior (i.e., the Sprague effect) but still could solve only the brightness task. The final four cats were controls and underwent no surgery; they demonstrated good retention of the pattern task despite an extensive idle period corresponding to the postoperative period before retesting the above ten cats. These data indicate that, while a transection of the collicular commissure after visual decortication dramatically improves visual orienting, it does not obviously improve visual discrimination abilities.