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Kendrick Kay, Kevin Weiner, Kalanit Grill-Spector; Spatial receptive fields persist at the latest stages of the human ventral visual stream. Journal of Vision 2014;14(10):717. doi: 10.1167/14.10.717.
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© ARVO (1962-2015); The Authors (2016-present)
Recent fMRI studies using multivariate pattern analysis have demonstrated sensitivity to position and size in high-level regions of human visual cortex. While this indicates that information exists in these regions, the precise nature of this information remains unclear. Here we demonstrate a new protocol that quantitatively maps the population receptive fields (pRFs) of individual voxels in face-selective regions of human visual cortex. We measured BOLD responses while subjects viewed faces that varied systematically in position and size. Faces were positioned on a 7 x 7 grid (extending up to 3.0째 eccentricity) and were presented at 3 different sizes (1.6째, 3.2째, 4.7째 diameter). We then analyzed the BOLD responses measured at each voxel using a computational model that characterizes pRF position and size (Kay et al., J. Neurophys., 2013). We show that the model accurately accounts for responses in face-selective regions IOG-faces/OFA, pFus-faces/FFA-1, and mFus-faces/FFA-2. Importantly, the model successfully generalizes to novel untrained positions and sizes. Examining model parameters, we find systematic changes in pRF properties, including larger and more foveal pRFs in anterior face-selective regions. To investigate whether attention affects pRF properties, we repeated the measurements while subjects engaged in different tasks (maintaining fixation). We find that compared to a rapid serial visual presentation task at fixation, when a task is performed on the faces, pRFs in face-selective regions, but not in early visual areas, exhibit a response gain, increase in size, and shift away from the fovea. In summary, our results demonstrate that spatial pRFs persist at the latest stages of the ventral visual stream. Furthermore, our findings indicate that neural responses at these stages contain not only information about the content of a stimulus but also precise and systematic information about its spatial location.
Meeting abstract presented at VSS 2014
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