Glass pattern responses in macaque V2 neurons.

Area V2 of macaque visual cortex is known to respond well to conventional oriented bar and grating stimuli, but some recent physiological data have shown that it may play an important role in coding more complicated patterns. Most of these data come from testing done with stimuli presented within the classical receptive field (CRF), whereas relatively little attention has been paid to the role played by the extra-classical surround. We have previously shown that neurons in primary visual cortex (V1) respond to translational Glass patterns in a manner that is predictable from their responses to grating stimuli. In this article, we first extend our experiments and modeling of Glass pattern responses in V1 to include V2. We explored the sensitivity of V2 cells to global form cues in Glass patterns confined to the CRF. Our results indicate that V2 neurons respond to the local signals in Glass patterns in a manner similar to V1 and that those responses are not influenced by global form present in the surround. It appears that the coding of the more complicated global structure in Glass patterns takes place further downstream in the visual system.