Rüdiger von der Heydt, Professor of Neuroscience at Johns Hopkins University, Krieger Mind/Brain Institute, will be giving a CompNet Seminar Talk on Friday, December 7, 2012 at 2:00 p.m. in the CompNet Building.
CompNet cordially invites you to attend the upcoming CompNet Seminar Talk.
Figure-ground organization and the emergence of object structure in the visual cortex
by Prof. Rüdiger von der Heydt
Professor of Neuroscience
Johns Hopkins University
Krieger Mind/Brain Institute
Friday, December 7, 2012
Auditorium - Basement Room B03
677 Beacon Street
A long history of studies of perception has shown that the visual system organizes the incoming information early on, interpreting the 2D image in terms of a 3D world, and producing a structure that enables object-based attention and tracking of object identity. Recordings from monkey visual cortex show that many neurons, especially in area V2, are selective for border ownership. These neurons are edge selective and have ordinary classical receptive fields, but in addition, their responses are modulated (enhanced or suppressed) depending on the location of a ‘figure’ relative to the edge in their receptive field. Each neuron has a fixed preference for location on one side or the other. This selectivity is derived from the image context far beyond the classical receptive field. In this talk I will review studies from my lab indicating that border ownership selectivity reflects mechanisms that define what we call proto-objects. We think the response enhancement is produced by recurrent input from grouping cells at a higher level, cells that we postulate, but have not directly studied so far. The evidence includes experiments showing (1) reversal of border ownership signals with change of perceived object structure, (2) border ownership specific enhancement of responses in object-based selective attention, (3) persistence of border ownership signals in accordance with continuity of object perception, and (4) remapping of border ownership signals across saccades and object movements. We propose that grouping mechanisms detect ‘objectness’ according to simple rules, and, via recurrent projections, provide a mechanism that allows top-down signals to selectively enhance the low-level feature signals representing an object. Additional circuits may provide persistence and remapping.