We measured brain activity during mental rotation and object recognition with objects rotated around three different axes. Activity in the superior parietal lobe (SPL) increased proportionally to viewpoint disparity during mental rotation, but not during object recognition. In contrast, the fusiform gyrus was preferentially recruited in a viewpoint-dependent manner in recognition as compared to mental rotation. In addition, independent of the effect of viewpoint, object recognition was associated with ventral areas and mental rotation with dorsal areas. These results indicate that the similar behavioral effects of viewpoint obtained in these two tasks are based on different neural substrates. Such findings call into question the hypothesis that mental rotation is used to compensate for changes in viewpoint during object recognition.
Bibliographical noteFunding Information:
Some of these results were reported at the 40 th annual meeting of the Psychonomic Society, Los Angeles, CA, November, 1999. This work was supported in part by NSF Award SBR-9615819 to M.J.T. and by NINDS Award NS33332 to J.C.G.; The authors would like to thank Kim Curby for assistance in preparing the materials for the experiment; Jill Moylan, Terry Hickey, and Hedy Sarofin for their help with data collection; and Kenneth Blum and three anonymous reviewers for their helpful comments.