Abstract
Integrating objects with their context is a key step in interpreting complex visual scenes. Here, we used functional Magnetic Resonance Imaging (fMRI) 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 vs. incongruent scenes in the lateral occipital complex, inferior temporal cortex, parahippocampal cortex, and prefrontal cortex. Importantly, and in contrast to previous studies, these activations could not be explained by task-induced conflict. A secondary goal of this study was to examine whether processing of object-context relations could occur in the absence of awareness. We found no evidence for brain activity differentiating between congruent and incongruent invisible masked scenes, which might reflect a genuine lack of activation, or stem from the limitations of our study. Overall, our results provide novel support for the roles of parahippocampal cortex and frontal areas in conscious processing of object-context relations, which cannot be explained by either low-level differences or task demands. Yet they further suggest that brain activity is decreased by visual masking to the point of becoming undetectable with our fMRI protocol.
Highlights
A very short glimpse of a visual scene often suffices to identify objects, and understand their relations with one another, as well as with the context in which they appear
Our results suggest that the posterior – and not solely the anterior – parahippocampal cortex (PHC), most likely corresponding to the Parahippocampal place area (PPA), is involved in processing contextual www.nature.com/scientificreports
Our findings seem to support the model suggested by Bar (2004) for scene processing. According to this model, during normal scene perception the visual cortex projects a blurred, low spatial-frequency representation early and rapidly to the prefrontal cortex (PFC; note that the model remains general about the exact areas within the PFC which are involved in the process, and that we found inferior and medial frontal activations) and parahippocampal cortex (PHC)
Summary
A very short glimpse of a visual scene often suffices to identify objects, and understand their relations with one another, as well as with the context in which they appear. The activated representations of such objects are compared with upcoming visual information about objects’ features, until a match is found and the objects are identified (for electrophysiological support, see9,16–19,though see[20]) These suggestions are mostly based on studies that did not directly examine the processing of objects embedded in scenes, but rather used other ways to probe contextual processing (e.g., comparing objects that evoke strong vs weak contextual associations[21], or manipulating the relations between two isolated objects[22,23]). The few papers that did focus on objects embedded in real life scenes[24,25,26] report conflicting findings about the role of frontotemporal regions - the prefrontal cortex (PFC) and the medial temporal lobe (MTL). Others argue that the PHC is solely dedicated to processing spatial layouts (the spatial layout hypothesis[35,36]; see [37] and[38] that support the spatial account, yet interestingly find effects of both the scene and its constituents on PHC activity), or representations of three-dimensional local spaces, even of a single object[39], irrespective of contextual associations[40]
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