Rapid recurrent processing gates awareness in primary visual cortex

C. N. Boehler; M. A. Schoenfeld; H.-J. Heinze; J.-M. Hopf

doi:10.1073/pnas.0801999105

New Research In

Edited by Michael I. Posner, University of Oregon, Eugene, OR, and approved May 1, 2008 (received for review March 4, 2008)

Abstract

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.

Footnotes

^‡To whom correspondence should be addressed at:
Department of Neurology II, Otto von Guericke University Magdeburg, Leipziger Strasse 44, 39120 Magdeburg, Germany.
E-mail: jens-max.hopf{at}medizin.uni-magdeburg.de
Author contributions: C.N.B., M.A.S., H.-J.H., and J.-M.H. designed research; C.N.B. performed research; C.N.B., M.A.S., and J.-M.H. analyzed data; and J.-M.H. wrote the paper.
The authors declare no conflict of interest.
This article is a PNAS Direct Submission.
© 2008 by The National Academy of Sciences of the USA

C. N. Boehler*,
M. A. Schoenfeld*,^†,
H.-J. Heinze*,^†, and
J.-M. Hopf*,^†,^‡

*Leibniz Institute for Neurobiology, D-39118 Magdeburg, Germany; and
^†Department of Neurology II, Otto von Guericke University Magdeburg, D-39120 Magdeburg, Germany

Edited by Michael I. Posner, University of Oregon, Eugene, OR, and approved May 1, 2008 (received for review March 4, 2008)

Abstract

magnetoencephalography
visual attention
visual awareness

Footnotes

^‡To whom correspondence should be addressed at:
Department of Neurology II, Otto von Guericke University Magdeburg, Leipziger Strasse 44, 39120 Magdeburg, Germany.
E-mail: jens-max.hopf{at}medizin.uni-magdeburg.de
Author contributions: C.N.B., M.A.S., H.-J.H., and J.-M.H. designed research; C.N.B. performed research; C.N.B., M.A.S., and J.-M.H. analyzed data; and J.-M.H. wrote the paper.
The authors declare no conflict of interest.
This article is a PNAS Direct Submission.

View Full Text