Imaging object-scene integration in visible and invisible natural scenes
Résumé
Integrating objects with their context is a key step in the interpretation of complex visual scenes.
Humans can do this very quickly, yet the brain mechanisms that mediate this ability are not yet
understood. Here, we used functional Magnetic Resonance Imaging (fMRI) to measure brain
activity while participants viewed visual scenes depicting a person performing an action with an
object that was either congruent or incongruent with the scene. Univariate and multivariate
analyses revealed different activity for congruent compared to incongruent scenes in the lateral
occipital complex, inferior temporal cortex, parahippocampal cortex, and prefrontal cortex, in
line with existing models of scene processing. Importantly, and in contrast to previous studies,
these activations could not be explained by task-induced conflicts. A secondary goal of this study
was to examine whether object-context integration could occur in the absence of awareness, by
comparing brain activity elicited by congruent vs. incongruent scenes that were suppressed from
awareness using visual masking. We found no evidence for brain activity differentiating between
congruent and incongruent invisible scenes. Overall, our results provide novel support for the
roles of PHC and PFC in conscious object-context integration which cannot be explained by
either low-level differences or task demands. Yet they further suggest that activity in these
regions is decreased by visual masking to the point of becoming undetectable with our fMRI
protocol.
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