Functional interactions between areas V1 and V2 in the monkey.

The role of feedback connections from area V2 to V1 was studied by reversible inactivation. When V2 was inactivated the responses of some V1 neurons to stimulation of the surround region were increased while responses to center stimulation were unchanged or decreased. Latencies to small flashing stimuli were also compared in areas V1 and V2. The distributions in the two areas overlap largely, with a 10 ms shift between the two. Neurons of V1 and V2 that are driven by the magnocellular layers of the LGN are activated 20 ms earlier than neurons of the parvocellular stream.