EEG Frequency Tagging Reveals the Integration of Form and Motion Cues into the Perception of Group Movement.
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ABSTRACT:
SUBMITTER: Cracco E
PROVIDER: S-EPMC9247417 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:When moving around in the world, the human visual system uses both motion and form information to estimate the direction of self-motion (i.e., heading). However, little is known about cortical areas in charge of this task. This brain-imaging study addressed this question by using visual stimuli consisting of randomly distributed dot pairs oriented toward a locus on a screen (the form-defined focus of expansion [FoE]) but moved away from a different locus (the motion-defined FoE) to simulate observer translation. We first fixed the motion-defined FoE location and shifted the form-defined FoE location. We then made the locations of the motion- and the form-defined FoEs either congruent (at the same location in the display) or incongruent (on the opposite sides of the display). The motion- or the form-defined FoE shift was the same in the two types of stimuli, but the perceived heading direction shifted for the congruent, but not for the incongruent stimuli. Participants (both sexes) made a task-irrelevant (contrast discrimination) judgment during scanning. Searchlight and ROI-based multivoxel pattern analysis revealed that early visual areas V1, V2, and V3 responded to either the motion- or the form-defined FoE shift. After V3, only the dorsal areas V3a and V3B/KO responded to such shifts. Furthermore, area V3B/KO shows a significantly higher decoding accuracy for the congruent than the incongruent stimuli. Our results provide direct evidence showing that area V3B/KO does not simply respond to motion and form cues but integrates these two cues for the perception of heading.SIGNIFICANCE STATEMENT Human survival relies on accurate perception of self-motion. The visual system uses both motion (optic flow) and form cues for the perception of the direction of self-motion (heading). Although human brain areas for processing optic flow and form structure are well identified, the areas responsible for integrating these two cues for the perception of self-motion remain unknown. We conducted fMRI experiments and used multivoxel pattern analysis technique to find human brain areas that can decode the shift in heading specified by each cue alone and the two cues combined. We found that motion and form cues are first processed in the early visual areas and then are likely integrated in the higher dorsal area V3B/KO for the final estimation of heading.
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Project description:Do we perceive a group of dancers moving in synchrony differently from a group of drones flying in-sync? The brain has dedicated networks for perception of coherent motion and interacting human bodies. However, it is unclear to what extent the underlying neural mechanisms overlap. Here we delineate these mechanisms by independently manipulating the degree of motion synchrony and the humanoid quality of multiple point-light displays (PLDs). Four PLDs moving within a group were changing contrast in cycles of fixed frequencies, which permits the identification of the neural processes that are tagged by these frequencies. In the frequency spectrum of the steady-state EEG we found two emergent frequency components, which signified distinct levels of interactions between PLDs. The first component was associated with motion synchrony, the second with the human quality of the moving items. These findings indicate that visual processing of synchronously moving dancers involves two distinct neural mechanisms: one for the perception of a group of items moving in synchrony and one for the perception of a group of moving items with human quality. We propose that these mechanisms underlie high-level perception of social interactions.
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Project description:PurposeThe purpose of this study was to assess motion-defined form perception, including the association with clinical and sensory factors that may drive performance, in each eye of children with deprivation amblyopia due to unilateral cataract.MethodsCoherence thresholds for orientation discrimination of motion-defined form were measured using a staircase procedure in 30 children with deprivation amblyopia and 59 age-matched controls. Visual acuity, stereoacuity, fusion, and interocular suppression were also measured. Fixation stability and fellow-eye global motion thresholds were measured in a subset of children.ResultsMotion-defined form coherence thresholds were elevated in 90% of children with deprivation amblyopia when viewing with the amblyopic eye and in 40% when viewing with the fellow eye. The deficit was similar in children with a cataract that had been visually significant at birth (congenital) and in children for whom the cataract appeared later in infancy or childhood (developmental). Poorer motion-defined form perception in amblyopic eyes was associated with poorer visual acuity, poorer binocular function, greater interocular suppression, and the presence of nystagmus. Fellow-eye deficits were not associated with any of these factors, but a temporo-nasal asymmetry for global motion perception in favor of nasalward motion suggested a general disruption in motion perception.ConclusionsDeficits in motion-defined form perception are common in children with deprivation amblyopia and may reflect a problem in motion processing that relies on binocular mechanisms.
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