title: Synaptic Correlates of Low-Level Perception in V1.
abstract: The computational role of primary visual cortex (V1) in low-level perception remains largely debated. A dominant view assumes the prevalence of higher cortical areas and top-down processes in binding information across the visual field. Here, we investigated the role of long-distance intracortical connections in form and motion processing by measuring, with intracellular recordings, their synaptic impact on neurons in area 17 (V1) of the anesthetized cat. By systematically mapping synaptic responses to stimuli presented in the nonspiking surround of V1 receptive fields, we provide the first quantitative characterization of the lateral functional connectivity kernel of V1 neurons. Our results revealed at the population level two structural-functional biases in the synaptic integration and dynamic association properties of V1 neurons. First, subthreshold responses to oriented stimuli flashed in isolation in the nonspiking surround exhibited a geometric organization around the preferred orientation axis mirroring the psychophysical "association field" for collinear contour perception. Second, apparent motion stimuli, for which horizontal and feedforward synaptic inputs summed in-phase, evoked dominantly facilitatory nonlinear interactions, specifically during centripetal collinear activation along the preferred orientation axis, at saccadic-like speeds. This spatiotemporal integration property, which could constitute the neural correlate of a human perceptual bias in speed detection, suggests that local (orientation) and global (motion) information is already linked within V1. We propose the existence of a "dynamic association field" in V1 neurons, whose spatial extent and anisotropy are transiently updated and reshaped as a function of changes in the retinal flow statistics imposed during natural oculomotor exploration.
  
  
  CONCLUSIONS
  The computational role of primary visual cortex in low-level perception remains debated. The expression of this "pop-out" perception is often assumed to require attention-related processes, such as top-down feedback from higher cortical areas. Using intracellular techniques in the anesthetized cat and novel analysis methods, we reveal unexpected structural-functional biases in the synaptic integration and dynamic association properties of V1 neurons. These structural-functional biases provide a substrate, within V1, for contour detection and, more unexpectedly, global motion flow sensitivity at saccadic speed, even in the absence of attentional processes. We argue for the concept of a "dynamic association field" in V1 neurons, whose spatial extent and anisotropy changes with retinal flow statistics, and more generally for a renewed focus on intracortical computation.
authors.affiliation: Unité de Neuroscience Information et Complexité (UNIC), Centre National de la Recherche Scientifique UPR-3293, 91198 Gif-sur-Yvette, France, Graduate School of the École Polytechnique, École Polytechnique, 91128 Palaiseau, France, Graduate School of Science and Engineering, Saitama University, Shimo-Okubo 255, Sakura-ku, Saitama-shi, 338-8570, Japan, and.
authors.forename: Florian
authors.initials: F
authors.lastname: Gerard-Mercier
authors.affiliation: Unité de Neuroscience Information et Complexité (UNIC), Centre National de la Recherche Scientifique UPR-3293, 91198 Gif-sur-Yvette, France.
authors.forename: Pedro V
authors.identifier: http://orcid.org/0000-0002-5666-9606
authors.initials: PV
authors.lastname: Carelli
authors.affiliation: Unité de Neuroscience Information et Complexité (UNIC), Centre National de la Recherche Scientifique UPR-3293, 91198 Gif-sur-Yvette, France, Université Paris-Sud, 91405 Orsay, France.
authors.forename: Marc
authors.initials: M
authors.lastname: Pananceau
authors.affiliation: Unité de Neuroscience Information et Complexité (UNIC), Centre National de la Recherche Scientifique UPR-3293, 91198 Gif-sur-Yvette, France.
authors.forename: Xoana G
authors.initials: XG
authors.lastname: Troncoso
authors.affiliation: Unité de Neuroscience Information et Complexité (UNIC), Centre National de la Recherche Scientifique UPR-3293, 91198 Gif-sur-Yvette, France, Graduate School of the École Polytechnique, École Polytechnique, 91128 Palaiseau, France, yves.fregnac@unic.cnrs-gif.fr.
authors.forename: Yves
authors.initials: Y
authors.lastname: Frégnac
mesh_terms: D000465:Algorithms; D000758:Anesthesia; D000818:Animals; D016880:Anisotropy; D001931:Brain Mapping; D002415:Cats; D005556:Form Perception / Q000502:physiology; D009039:Motion Perception / Q000502:physiology; D009474:Neurons / Q000502:physiology; D017711:Nonlinear Dynamics; D010775:Photic Stimulation; D011930:Reaction Time / Q000502:physiology; D012160:Retina / Q000502:physiology; D013569:Synapses / Q000502:physiology*; D014793:Visual Cortex / Q000166:cytology / Q000502:physiology*; D014794:Visual Fields / Q000502:physiology; D014795:Visual Pathways / Q000502:physiology; D014796:Visual Perception / Q000502:physiology*
keywords: apparent motion sensitivity; horizontal connectivity; perceptual association field; primary visual cortex; synaptic receptive field