Pattern discrimination following removal of visual neocortex in the cat

Three cats were trained on brightness and pattern discrimination tasks for food reward in an automated two-choice discrimination apparatus. The pattern stimuli were horizontal vs. vertical stripes and were designed so that total luminous flux was equated and consistent local luminous flux cues were eliminated between the two stimuli. The cats then underwent removal of visual neocortex, in one case including all of areas 17, 18, and most or all of 19, as determined by detailed histological criteria. The brightness discrimination habit was lost after surgery and was relearned by all subjects in slightly more trials than were required preoperatively. All cats were also able to relearn the pattern discrimination, although from two to ten times the number of preoperative trials were required. Trials to criterion were not related to lesion extent. Tests indicated that the pattern discrimination was visually guided and that postoperative pattern discrimination and visual placing were dependent on stimulus illumination and contrast. Optokinetic nystagamus, simple visual reactions, and general behavior were also tested postoperatively with results similar to those reported by other investigators. Comparison of the present experiment with previous investigations suggested that stimulus illumination and contrast, stimulus configuration, and amount of postoperative training are critical variables in the elaboration of visual pattern discrimination in the visually neodecorticated cat.