HIGH-LEVEL OBJECT RECOGNITION WITHOUT AN ANTERIOR INFERIOR TEMPORAL-LOBE

Seven individuals with unilateral anterior inferior temporal (AIT) lob ectomies performed two types of shape recognition tasks with line draw ings of 3D objects briefly presented in either the left or the right v isual held. In one task, subjects named familiar objects in a name pri ming paradigm. In the other task, subjects judged whether two objects, presented sequentially with an intervening mask, were the same or dif ferent in shape, disregarding differences in orientation of up to 60 d egrees in depth. They could not use names or basic level concepts to d o the matching as the stimuli were either nonsense objects or, if fami liar objects, were of same name-different-shaped exemplars on differen t trials. The disadvantage of presenting an image to the lobectomized hemisphere was negligible in both tasks. Two non-exclusive possibiliti es are suggested by this result: (a) Object recognition is completed p osterior to AIT, likely at the temporal-occipital boundary, with no de leterious retrograde effects on object recognition from the AIT sectio n, or (b) Callosal transfer of object information prior to AIT is comp letely efficient. These results, along with results of single unit rec ording and lesion experiments in the monkey, PET and MRI imaging in hu mans, and a plausibility argument based on the pattern of callosal con nections suggest both are correct. Rather than mediating real-time obj ect recognition, AIT may code representations for visual episodes and scenes. (C) 1997 Elsevier Science Ltd.