The primate visual system after bilateral removal of striate cortex. Survival of complex pattern vision

This study examined the strategies used by monkeys lacking striate cortex to perform visual pattern discriminations. Complete bilateral removal of area 17 initially produced severe visual impairment with recovery of even rudimentary visual capacities (e. g., flux discrimination) dependent on gradually retraining the monkeys through a set of increasingly more complex pattern discriminations. After extended periods of postoperative testing, however, three of five monkeys lacking striate cortex were able to discriminate a number of complex visual patterns even when such local stimulus cues as amount of contour and number of elements were equal. Further testing demonstrated that these animals could distinguish a pattern's spatial organization. They were also able to transfer good performance to tasks with novel patterns.