We can discriminate objects even if they are seen from different viewing angles. It had been believed that view-invariant object recognition across similar objects develops through the experience of successively viewing different views of each object. However we have found previously that after monkeys learned to discriminate individual views of objects, they were able to recognize objects across rotations up to 60 deg. In the present study, we further investigated responses of neurons in the inferotemporal cortex (IT) of monkeys to the object images with different prior experiences. We created six object sets each of which consisted of four similar objects seen from 4 viewing angles with 30 deg intervals. Each of the two monkeys used in the present study experienced 6 object sets in three different tasks, 2 sets in each task. Same-or-not task was a simple viewing without discrimination within the object set, Image task required discrimination of the images within each object set in the same viewing angles, and Object task required view-invariant object discrimination. We found that the viewing angle tuning of the IT neurons responding to the object images with the prior experience of the Image task was similar to that of the IT neurons responding to the object images with the prior experience of the Object task, and different from that of the IT neurons responding to the object images with the prior experience of the Same-or-not task. The results suggest that view-invariant neuronal representations in the IT developed through the experience of discrimination of similar objects in the same viewing angles.
