[koglist] Reminder: [CDC Seminars] CogSci CEU Departmental Colloquium: April 17, Wednesday: Frederic Chavane (CNRS & Aix-Marseille University, Marseille, France) - Functional roles of lateral interactions in the visual cortex

The CEU Department of Cognitive Science cordially invites you to a talk (as part of its Departmental Colloquium series) by Prof. Frederic Chavane, CNRS & Aix-Marseille University, Marseille, France Date: Wednesday, April 17, 2013 - 17:00 - 18:30 Location: Department of Cognitive Science, CEU, Budapest, Frankel Leó út 30-34., Room G15 Functional roles of lateral interactions in the visual cortex Sensory stimuli are encoded by large neuronal populations that have to elaborate rapid and robust representation of the input image. This is a computational challenge since these inputs are ambiguous, dynamical, segmented into a myriad of piecewise cues and constantly influenced by frequent eye movements. To overcome this problem, our visual system must link sensory inputs with a priori knowledge at multiple spatial and temporal scales. One important candidate for these lateral interactions are the intra-cortical axons that dynamically links neurons separated by millimeters in the cortical tissue, the so-called �horizontal� connectivity. This connectivity functionally subtend lateral interactions within these cortical areas that are usually organized into cartographical functional maps. In the primary visual cortex, that possesses a retinotopic organization, the horizontal connectivity generates spreads of activity that links together cortical columns sensitive for displaced regions of the visual field (1, 2). In this talk, I will present experimental evidences using optical imaging of voltage sensitive dye that suggests that lateral interactions in the primary visual cortex play indeed a key role in several key neural computations at the level of neuronal populations, ranging from input normalization to stimulus representation. First I will show that any local stimulus is dynamically normalized through lateral interactions as a function of the context in which it is embedded (3). In a second series of experiment, I will provide evidence that such spatio-temporal normalization can then lead to the emergence of motion signal in response to a sequence of static images, a cortical correlate of motion illusions (4, 5). These results suggest that lateral interactions within a cortical area plays a major role in shaping visual processing at the mesoscopic population scale, setting the conditions for an optimal decoding by downstream areas. 1. V. Bringuier, F. Chavane, L. Glaeser, Y. Fr�gnac, Science 283, 695�699 (1999). 2. F. Chavane et al., Front Syst Neurosci 5, 1�26 (2011). 3. A. Reynaud, G. S. Masson, F. Chavane, Journal of Neuroscience 32, 12558�12569 (2012). 4. D. Jancke, F. Chavane, S. Naaman, A. Grinvald, Nature 428, 423�426 (2004). 5. F. Chavane, A. Reynaud, G. Masson, JOV 8, 226�226 (2008). We're looking forward to see you there (Frankel Leo u. 30-34) ! Cognitive Science Events at CEU: http://cognitivescience.ceu.hu/events