title: Figure-ground processing during fixational saccades in V1: indication for higher-order stability.
abstract: In a typical visual scene we continuously perceive a "figure" that is segregated from the surrounding "background" despite ongoing microsaccades and small saccades that are performed when attempting fixation (fixational saccades [FSs]). Previously reported neuronal correlates of figure-ground (FG) segregation in the primary visual cortex (V1) showed enhanced activity in the "figure" along with suppressed activity in the noisy "background." However, it is unknown how this FG modulation in V1 is affected by FSs. To investigate this question, we trained two monkeys to detect a contour embedded in a noisy background while simultaneously imaging V1 using voltage-sensitive dyes. During stimulus presentation, the monkeys typically performed 1-3 FSs, which displaced the contour over the retina. Using eye position and a 2D analytical model to map the stimulus onto V1, we were able to compute FG modulation before and after each FS. On the spatial cortical scale, we found that, after each FS, FG modulation follows the stimulus retinal displacement and "hops" within the V1 retinotopic map, suggesting visual instability. On the temporal scale, FG modulation is initiated in the new retinotopic position before it disappeared from the old retinotopic position. Moreover, the FG modulation developed faster after an FS, compared with after stimulus onset, which may contribute to visual stability of FG segregation, along the timeline of stimulus presentation. Therefore, despite spatial discontinuity of FG modulation in V1, the higher-order stability of FG modulation along time may enable our stable and continuous perception.
authors.affiliation: Gonda Multidisciplinary Brain Research Center, Bar-Ilan University, Ramat Gan, 52900 Israel.
authors.forename: Ariel
authors.initials: A
authors.lastname: Gilad
authors.forename: Yair
authors.initials: Y
authors.lastname: Pesoa
authors.forename: Inbal
authors.initials: I
authors.lastname: Ayzenshtat
authors.forename: Hamutal
authors.initials: H
authors.lastname: Slovin
mesh_terms: D000818:Animals; D001931:Brain Mapping; D005403:Fixation, Ocular / Q000502:physiology*; D005556:Form Perception / Q000502:physiology*; D008252:Macaca fascicularis; D008297:Male; D010775:Photic Stimulation; D011930:Reaction Time; D018709:Statistics, Nonparametric; D014793:Visual Cortex / Q000502:physiology*; D014795:Visual Pathways / Q000502:physiology; D056969:Voltage-Sensitive Dye Imaging
keywords: contour integration; figure-ground; fixational saccades; primary visual cortex; visual stability; voltage-sensitive dye imaging