Effective connectivity in the cerebral network underlying visual scene categorization. A dynamic causal modeling study

Abstract : According to current models of visual perception (Kauffmann, Ramanoël, & Peyrin, 2014; Schyns & Oliva, 1994) scenes are processed in terms of spatial frequencies following a predominantly coarse-to-fine processing sequence. Low spatial frequencies (LSF) reach high-order areas rapidly in order to activate plausible interpretations of the visual input. This triggers top-down facilitation that guides subsequent processing of high spatial frequencies (HSF) in lower-level areas such as the inferotemporal and occipital cortices (Bar et al., 2006; Bullier, 2001; Peyrin et al., 2010). However, dynamic interactions underlying top-down influences on the occipital cortex have never been systematically investigated. The present fMRI study aimed to further explore the neural bases and effective connectivity underlying coarse-to-fine processing of scenes, particularly the role of the occipital cortex. We used sequences of six filtered scenes as stimuli depicting coarse-to-fine or fine-to-coarse processing of scenes. Participants performed a categorization task on these stimuli (indoor vs. outdoor). Firstly, we showed that coarse-to-fine (compared to fine-to-coarse) sequences elicited stronger activation in the inferior frontal gyrus (in the orbitofrontal cortex), the inferotemporal cortex (in the fusiform and parahippocampal gyri), and the occipital cortex (in the cuneus). Dynamic causal modeling (DCM; Friston, Harrison, & Penny, 2003) was then used to infer effective connectivity between these regions. DCM results revealed that coarse-to-fine processing resulted in increased connectivity from the occipital cortex to the inferior frontal gyrus and from the inferior frontal gyrus to the inferotemporal cortex. Critically, results also revealed an increase in connectivity strength from both the inferior frontal gyrus and the inferotemporal cortex to the occipital cortex, suggesting top-down influences from these areas that may guide processing of incoming signals. The present results support influential models of visual perception and refine them by emphasizing the role of the occipital cortex as a cortical site for feedback projections in the neural network underlying coarse-to-fine processing of scenes.
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Poster communications
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http://hal.univ-grenoble-alpes.fr/hal-01982397
Contributor : Carole Peyrin <>
Submitted on : Tuesday, January 15, 2019 - 4:10:28 PM
Last modification on : Thursday, January 17, 2019 - 1:04:44 AM

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Louise Kauffmann, Alan Chauvin, Cedric Pichat, Carole Peyrin. Effective connectivity in the cerebral network underlying visual scene categorization. A dynamic causal modeling study. Congrès de la Société Française de Résonance Magnétique en Biologie et Médecine, Mar 2015, Grenoble, France. ⟨hal-01982397⟩

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