Depth discrimination in rats following removal of visual neocortex

Following complete removal of visual neocortex, 4 rats were successfully trained, using shock motivation, to discriminate between patterned depth stimuli that were of unequal distances. The rats were subsequently retrained on the same problem as luminous flux, linear perspective and local luminosity cues were successively eliminated or greatly reduced. Further training on other discrimination problems indicated it to have been unlikely that small, uncontrollable luminosity cues guided the discrimination performances, yet the same rats appeared incapable of learning a 2-dimensional planometric pattern discrimination following extensive training. In a second experiment the performances of rats lacking visual neocortex ( n = 9) were found to be inferior to those of normal rats ( n = 12) on the depth problem. These results are discussed in relation to the literature concerning the visual capacities of rats lacking visual cortex.