Goal : to locate areas of the macaque brain involved in processing form.

1. USING GLASS PATTERNS AND fMRI TO IDENTIFY AREAS THAT PROCESS GLOBAL FORM IN MACAQUE VISUAL CORTEX. 1. Max-Planck-Institute for Biological Cybernetics, Spemannstrasse 38, D-72076 Tübingen, Germany; 2. Center for Neural Science, New York University, N.Y., N.Y. 100033. 3. Present address: Dept. of Psychological and Brain Sciences, Dartmouth College, Hanover N.H. 03755; Peter.Tse@dartmouth.edu Tse1,3, P. U., Smith2, M. A., Augath1, M., Trinath T. 1, Logothetis N.K. 1, and Movshon2, J. A. 286.6 Goal: to locate areas of the macaque brain involved in processing form. Stimuli:Natural objects are not ideal stimuli because their form-defining characteristics are difficult to isolate, parameterize, or control. Glass patterns, created by pairing each dot in a random texture with another at a specified spatial offset (Glass 1969, Nature), are useful because form is defined by the global statistics of dot placement with spatial correlations that are purely local. Wilson et al (1997, VR) showed that concentric Glass patterns are processed more efficiently than other patterns with the same local but differing global statistics, suggesting that there exist higher-order 'grouping' filters tuned to particular patterns of activation among local filters. Glass patterns are created by pairing each dot in a random texture with another at a specified spatial offset. They are well-controlled because the number of dot pairs is constant across stimulus type. Patterns were: 1. 9-frame concentric, 2. 9-frame radial, 3. Randomly oriented dot pairs, 4. 9-frame translational, 5. Translational. Results 1: GLM contrasts showing V1 activation Logic: Differences in the BOLD signal between Glass Patterns will arise in brain areas that process non-local relationships among dot pairs. Method: We generated static and dynamic Glass patterns with different global forms, and used these to activate visual cortex in anesthetized monkeys. Eight-segment T2* weighted EPI fMRI images (13 slices, FOV=12.5, matrix=128x128) were collected on a 4.7T/40cm Biospec vertical scanner with 50mT/m gradients, using quadrature transmit/receive RF coils and gradient-recalled EPI fMRI sequences. Voxel volume was 0.5x0.5x2mm, TE=40ms, TR=750, and FA=20 to 25 degrees. translational x 9 translational x 9 concentric x 9 concentric x 9 random translational translational random radial x 9 radial x 9 # of brain volumes (16 minutes) 1: +concentric -random Results 2: One monkey of three showed signal in V4 + - icon1 icon2 1: +concentric -translational 3: +concentric -translational + - Results: All GPs vs. Blank Monkey 1 2: +concentric -random + - 1. 2. 3. • Conclusion: • BOLD signal in V1/V2 (and perhaps V4) is greater for certain Glass Patterns than others in the anaesthetized macaque. This may reveal processing of large-scale spatial correlations by neural networks in these areas. Monkey 2 2: +9frame transl.-translational 4. 5. + - Our five Glass Patterns translational x 9 translational x 9 concentric x 9 translational concentric x 9 translational radial x 9 radial x 9 random random Monkey 3 # of brain volumes (16 minutes) The lack of activation anterior to the lunate in these scans may be an effect of anaesthesia.