Johns Hopkins University, Department of Neuroscience

Neural population representation of a heart-shaped stimulus, derived from response rates of curvature/position-tuned cells in area V4. The left-hand horizontal axis represents boundary curvature, running from -0.3 (concave) through 0.0 (straight) to 1.0 (sharp convex). The right-hand horizontal axis represents object-centered position in degrees, with 0° corresponding to "right", 90° to "top", 180° to "left", and 270° to "bottom" relative to center of mass. The vertical axis (as well as color) represents response strength, derived by summing tuning functions across the cell population, with each cell's tuning function weighted by the cell's response to the heart-shaped stimulus. The surface contains two peaks near curvature 0.7 (broad convex) at positions 45° (upper right) and 135° (upper left), one peak at curvature 1.0 (sharp convex) and position 270° (bottom), and smaller peaks representing intervening concavities. These of course are the defining boundary features of a classic "heart" shape
 
© 2005 Department of Neuroscience, Johns Hopkins University School of Medicine