Representation of Local Figure-Ground by a Group of V4 Cells

Figure-ground (FG) segregation is a crucial function of the intermediate-level vision. Physiological studies on monkey V2 have reported border-ownership (BO) selective cells that signal the direction of figure along a local border. However, local borders in natural images are often complicated and they often do not provide a clue for FG segregation. In the present study, we hypothesize that a population of V4 cells represents FG by means of surface rather than border. We investigated this hypothesis by the computational analysis of neural signals from multiple cells in monkey V4. Specifically, we applied Support Vector Machine as an ideal integrator to the cellular responses, and examined whether the responses carry information capable of determining correct local FG. Our results showed that the responses from several tens of cells are capable of determining correct local FG in a variety of natural image patches while single-cell responses hardly determine FG, suggesting a population coding of local FG by a small number of cells in V4.