INHOMOGENEITIES IN THE STRUCTURE OF V1 ORIENTATION MAPS AND THEIR CONSEQUENCES FOR CORTICAL FUNCTION V. Dragoi*; M. Sur Brain & Cognitive Sci, MIT, Cambridge, MA, USA It is generally assumed that adult V1 is uniform in its capacity for plasticity, and that the response properties of neurons are relatively uniform within a given layer. Using a combination of intrinsic signal imaging, multiple-electrode recording, and visual psychophysics, we investigate here the effect of two types of inhomogeneities in the layout of V1 orientation maps: the inhomogeneous rate of change of orientation preference across the cortex (pinwheel centers vs. orientation domains) and the asymmetry in the size of orientation domains (cardinal vs. oblique domains). We used short-term adaptation to a stimulus of fixed orientation to induce changes in the tuning properties of neurons at selected cortical locations. We found a significant correlation between the orientation distribution of local inputs (<500um) and the adaptation-induced changes in preferred orientation and firing rate. These changes are pronounced when neurons integrate broadly tuned oriented inputs (recording site close to a pinwheel center or within an oblique orientation domain), whereas neurons retain stable response properties when the local orientation distribution is tuned (recording site in the middle of a cardinal orientation domain). We have tested the implications of these results for perception by demonstrating that human observers report different adaptation-induced changes in orientation tuning between cardinal and oblique axes. We suggest that preferential cortical locations for adaptive changes may be a strategy that the visual cortex employs to enable plasticity as well as stability in the face of adaptation to the statistics of natural images. Supported by McDonnell-Pew and Merck fellowships to V.D. and by NIH grant to M.S.