title: Gravity influences top-down signals in visual processing.
abstract: Visual perception is not only based on incoming visual signals but also on information about a multimodal reference frame that incorporates vestibulo-proprioceptive input and motor signals. In addition, top-down modulation of visual processing has previously been demonstrated during cognitive operations including selective attention and working memory tasks. In the absence of a stable gravitational reference, the updating of salient stimuli becomes crucial for successful visuo-spatial behavior by humans in weightlessness. Here we found that visually-evoked potentials triggered by the image of a tunnel just prior to an impending 3D movement in a virtual navigation task were altered in weightlessness aboard the International Space Station, while those evoked by a classical 2D-checkerboard were not. Specifically, the analysis of event-related spectral perturbations and inter-trial phase coherency of these EEG signals recorded in the frontal and occipital areas showed that phase-locking of theta-alpha oscillations was suppressed in weightlessness, but only for the 3D tunnel image. Moreover, analysis of the phase of the coherency demonstrated the existence on Earth of a directional flux in the EEG signals from the frontal to the occipital areas mediating a top-down modulation during the presentation of the image of the 3D tunnel. In weightlessness, this fronto-occipital, top-down control was transformed into a diverging flux from the central areas toward the frontal and occipital areas. These results demonstrate that gravity-related sensory inputs modulate primary visual areas depending on the affordances of the visual scene.
authors.affiliation: Laboratory of Neurophysiology and Biomechanics of Movement, ULB Neuroscience Institut, Université Libre de Bruxelles, Brussels, Belgium ; Laboratory of Electrophysiology, Université de Mons, Mons, Belgium.
authors.forename: Guy
authors.initials: G
authors.lastname: Cheron
authors.affiliation: Laboratory of Neurophysiology and Biomechanics of Movement, ULB Neuroscience Institut, Université Libre de Bruxelles, Brussels, Belgium.
authors.forename: Axelle
authors.initials: A
authors.lastname: Leroy
authors.affiliation: Laboratory of Neurophysiology and Biomechanics of Movement, ULB Neuroscience Institut, Université Libre de Bruxelles, Brussels, Belgium.
authors.forename: Ernesto
authors.initials: E
authors.lastname: Palmero-Soler
authors.affiliation: Laboratory of Neurophysiology and Biomechanics of Movement, ULB Neuroscience Institut, Université Libre de Bruxelles, Brussels, Belgium ; Laboratory of Electrophysiology, Université de Mons, Mons, Belgium.
authors.forename: Caty
authors.initials: C
authors.lastname: De Saedeleer
authors.affiliation: Laboratory of Neurophysiology and Biomechanics of Movement, ULB Neuroscience Institut, Université Libre de Bruxelles, Brussels, Belgium.
authors.forename: Ana
authors.initials: A
authors.lastname: Bengoetxea
authors.affiliation: Laboratory of Neurophysiology and Biomechanics of Movement, ULB Neuroscience Institut, Université Libre de Bruxelles, Brussels, Belgium.
authors.forename: Ana-Maria
authors.initials: AM
authors.lastname: Cebolla
authors.affiliation: Laboratoire de Physiologie de la Perception et de l'Action, CNRS Collège de France, Paris, France.
authors.forename: Manuel
authors.initials: M
authors.lastname: Vidal
authors.affiliation: Laboratory of Neurophysiology and Biomechanics of Movement, ULB Neuroscience Institut, Université Libre de Bruxelles, Brussels, Belgium.
authors.forename: Bernard
authors.initials: B
authors.lastname: Dan
authors.affiliation: Laboratoire de Physiologie de la Perception et de l'Action, CNRS Collège de France, Paris, France.
authors.forename: Alain
authors.initials: A
authors.lastname: Berthoz
authors.affiliation: Centre d'Etude de la Sensorimotricité (UMR 8194), Institut Neurosciences et Cognition, CNRS - Université Paris Descartes, Paris, France.
authors.forename: Joseph
authors.initials: J
authors.lastname: McIntyre
mesh_terms: D000328:Adult; D001921:Brain / Q000502:physiology; D058256:Brain Waves; D004569:Electroencephalography; D005074:Evoked Potentials, Visual; D006112:Gravitation; D006801:Humans; D008297:Male; D008875:Middle Aged; D010775:Photic Stimulation; D014796:Visual Perception / Q000502:physiology*