Rapid recurrent processing gates awareness in primary visual cortex

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 105; no. 25; pp. 8742 - 8747
• Main Authors: Boehler, C.N, Schoenfeld, M.A, Heinze, H.-J, Hopf, J.-M
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences 24.06.2008; National Acad Sciences
• Subjects: Adult; Attention - physiology; Awareness - physiology; Behavioral neuroscience; Biological Sciences; Brain; Brain Mapping; cerebral cortex; cortex; Data processing; Experimentation; Female; Humans; Hypotheses; Magnetic Resonance Imaging; Male; Monkeys; Neurons; NMR; Nuclear magnetic resonance; Quadrants; Sensors; vision; Visual cortex; Visual Cortex - physiology; Visual perception; Visual Perception - physiology; Visual task performance; Waveforms
• ISSN: 0027-8424; 1091-6490; 1091-6490
• DOI: 10.1073/pnas.0801999105

Visual awareness has been proposed to depend on recurrent processing in early visual cortex areas including the primary visual cortex (V1). Here, we address this hypothesis with high spatiotemporal resolution magnetoencephalographic recordings in subjects performing a substitution masking paradigm. Neural activity reflecting awareness is assessed by directly comparing the neuromagnetic response elicited by effectively and ineffectively masked targets after the proportion of trials leading to masking was individually adjusted to match the proportion of trials without masking. This revealed a modulation of recurrent activity in the primary visual cortex rapidly after the onset of the feedforward sweep of processing in striate and extrastriate areas but significantly before the onset of attention-dependent recurrent modulations in V1. Our data provide direct support for the notion that (i) recurrent processing in V1 correlates with visual awareness and (ii) that attention and awareness involve distinct recurrent processing operations.