Michael Epstein^1,2 (mlepstein88@gmail.com), Emil Olsson³, Juneau Wang², Karen Tian², Brian Maniscalco³, Jennifer Motzer², Diana Gamboa², Angela Shen³, Minh Nguyen³, Meera Sriram³, Sydney Liu³, Olenka Graham Castaneda³, Maggie Zhang³, Vanessa Wu³, Richard Brown^4,5, Victor Lamme⁶, Hakwan Lau⁷, Biyu He¹, Jan Brascamp⁸, Ned Block¹, David Chalmers¹, Megan Peters³, Rachel Denison²; ¹New York University, ²Boston University, ³University of California, Irvine, ⁴LaGuardia Community College, ⁵The Graduate Center, CUNY, ⁶University of Amsterdam, ⁷Institute for Basic Science, ⁸Michigan State University

Background: Figure-ground processing is a critical early step of object and scene perception. Although attention has been suggested to enhance figure-ground processing, there is limited neuroimaging work testing how attention influences visual cortical activity during figure-ground texture segmentation. In an fMRI experiment (27 participants with four sessions each), we tested whether spatial attention cues boost figure-ground processing in early visual cortex. Methods: Participants viewed four texture-defined figure-ground oval stimuli in each quadrant of the screen (3x4°, 5° from fixation, 250 ms duration). Textures were composed of parallel line elements tilted +/-45°. Oval figures within the texture were defined by orthogonal line orientations relative to the background. Stimuli were independently balanced across trials to be figure-present or figure-absent, have vertical or horizontal oval orientation, and display at one of five thresholded strength levels, based on the length of the texture line elements. Participants were pre-cued on each trial to attend a given quadrant and report the orientation of the oval in that quadrant, along with their subjective visibility of the oval (behavioral results to be reported elsewhere). Results: Given findings that figure-ground processing shows a center-surround structure, we grouped voxels based on their mean signal across conditions—either responding more to the figure than the background (figure-positive voxels) or more to the background than the figure (figure-negative voxels). We evaluated how attention affected BOLD responses within these two groups of voxels, comparing trials in which the oval figure was present vs. absent. In figure-positive voxels, attention increased responses to the figure relative to the background, whereas in figure-negative voxels, attention reduced responses to the figure relative to the background. Conclusions: Our results suggest that attention facilitates figure-ground processing by both enhancing the figure and suppressing the ground within visual cortex.

Acknowledgements: Templeton World Charity Foundation 0567 to BH, JB, NB, DC, MP, and RD, startup funding from the University of California Irvine and support from the Canadian Institute of Advanced Research to MP, startup funding from Boston University to RD, and BU UROP funding to DG.