title: Population response to contextual influences in the primary visual cortex.
abstract: Collinear proximal flankers can facilitate the detection of a low-contrast target or generate false-alarm target detection in the absence of a target. Although these effects are known to involve subthreshold neuronal interactions beyond the classical receptive field, the underlying neuronal mechanisms are not fully understood. Here, we used voltage-sensitive dye imaging that emphasizes subthreshold population activity, at high spatial and temporal resolution and imaged the visual cortex of fixating monkeys while they were presented with a low-contrast Gabor target, embedded within collinear or orthogonal flankers. We found that neuronal activity at the target site in area primary visual cortex increased and response latency decreased due to spatial spread of activation from the flankers' site. This increased activity was smaller than expected by a linear summation. The presentation of flankers alone induced strong spatial filling-in at the target site. Importantly, the increased neuronal activity at the target site was synchronized over time, both locally and with neuronal population at the flanker's site. This onset synchronization was higher for collinear than for orthogonal flankers. We further show that synchrony is a superior code over amplitude, for discriminating collinear from orthogonal pattern. These results suggest that population synchrony can serve as a code to discriminate contextual effects.
authors.affiliation: Gonda Multidisciplinary Brain Research Center, Bar-Ilan University, Ramat Gan, Israel.
authors.forename: Elhanan
authors.initials: E
authors.lastname: Meirovithz
authors.forename: Inbal
authors.initials: I
authors.lastname: Ayzenshtat
authors.forename: Yoram S
authors.initials: YS
authors.lastname: Bonneh
authors.forename: Royi
authors.initials: R
authors.lastname: Itzhack
authors.forename: Uri
authors.initials: U
authors.lastname: Werner-Reiss
authors.forename: Hamutal
authors.initials: H
authors.lastname: Slovin
mesh_terms: D000200:Action Potentials / Q000502:physiology*; D000818:Animals; D005074:Evoked Potentials, Visual / Q000502:physiology*; D005456:Fluorescent Dyes; D008252:Macaca fascicularis; D008297:Male; D009415:Nerve Net / Q000033:anatomy & histology / Q000502:physiology*; D009474:Neurons / Q000502:physiology*; D009483:Neuropsychological Tests; D010775:Photic Stimulation; D009435:Synaptic Transmission / Q000502:physiology; D014793:Visual Cortex / Q000033:anatomy & histology / Q000502:physiology*; D014796:Visual Perception / Q000502:physiology*; D056969:Voltage-Sensitive Dye Imaging / Q000379:methods
chemical_list: D005456:Fluorescent Dyes