Two functional magnetic resonance imaging (fMRI) face viewpoint adaptation experiments were conducted to investigate whether fMRI adaptation in high-level visual cortex depends on the duration of adaptation and how different views of a face are represented in the human visual system. We found adaptation effects in multiple face-selective areas, which suggest a distributed, viewer-centered representation of faces in the human visual system. However, the nature of the adaptation effects was dependent on the length of adaptation. With long adaptation durations, face-selective areas along the hierarchy of the visual system gradually exhibited viewpoint-tuned adaptation. As the angular difference between the adapter and test stimulus increased, the blood oxygen level-dependent (BOLD) signal evoked by the test stimulus gradually increased as a function of the amount of 3-dimensional (3D) rotation. With short adaptation durations, however, face-selective areas in the ventral pathway, including the lateral occipital cortex and right fusiform area, exhibited viewpoint-sensitive adaptation. These areas showed an increase in the BOLD signal with a 3D rotation, but this signal increase was independent of the amount of rotation. Further, the right superior temporal sulcus showed little or very weak viewpoint adaptation with short adaptation durations. Our findings suggest that long- and short-term fMRI adaptations may reflect selective properties of different neuronal mechanisms.
Bibliographical noteFunding Information:
We thank Yi Jiang for his assistance in collecting some data, Thomas Carlson for helping us to generate some of the stimuli, and Wilma Koutstaal for her helpful comments. This research was supported by the National Geospatial-Intelligence Agency (HM1582-05-C-0003), the James S. McDonnell Foundation, National Institutes of Health (NIH R01 EY015261-01), NIH National Center for Research Resources (NCRR) P41 RR008079, and the Mental Illness and Neuroscience Discovery (MIND) Institute. FF was also supported by the Eva O. Miller Fellowship and the Doctoral Dissertation Fellowship from the University of Minnesota. The 3D face model is from Max Planck Institute for Biological Cybernetics. Conflict of Interest: None declared.
- Visual cortex