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Top-down Modulations in the Visual Form Pathway Revealed with Dynamic Causal Modeling
Perception entails interactions between activated brain visual areas and the records of previous sensations, allowing for processes like figure–ground segregation and object recognition. The aim of this study was to characterize top-down effects that originate in the visual cortex and that are invol...
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Formato: | Texto |
Lenguaje: | English |
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Oxford University Press
2011
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Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3041008/ https://www.ncbi.nlm.nih.gov/pubmed/20621984 http://dx.doi.org/10.1093/cercor/bhq122 |
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author | Cardin, Velia Friston, Karl J. Zeki, Semir |
author_facet | Cardin, Velia Friston, Karl J. Zeki, Semir |
author_sort | Cardin, Velia |
collection | PubMed |
description | Perception entails interactions between activated brain visual areas and the records of previous sensations, allowing for processes like figure–ground segregation and object recognition. The aim of this study was to characterize top-down effects that originate in the visual cortex and that are involved in the generation and perception of form. We performed a functional magnetic resonance imaging experiment, where subjects viewed 3 groups of stimuli comprising oriented lines with different levels of recognizable high-order structure (none, collinearity, and meaning). Our results showed that recognizable stimuli cause larger activations in anterior visual and frontal areas. In contrast, when stimuli are random or unrecognizable, activations are greater in posterior visual areas, following a hierarchical organization where areas V1/V2 were less active with “collinearity” and the middle occipital cortex was less active with “meaning.” An effective connectivity analysis using dynamic causal modeling showed that high-order visual form engages higher visual areas that generate top-down signals, from multiple levels of the visual hierarchy. These results are consistent with a model in which if a stimulus has recognizable attributes, such as collinearity and meaning, the areas specialized for processing these attributes send top-down messages to the lower levels to facilitate more efficient encoding of visual form. |
format | Text |
id | pubmed-3041008 |
institution | National Center for Biotechnology Information |
language | English |
publishDate | 2011 |
publisher | Oxford University Press |
record_format | MEDLINE/PubMed |
spelling | pubmed-30410082011-12-05 Top-down Modulations in the Visual Form Pathway Revealed with Dynamic Causal Modeling Cardin, Velia Friston, Karl J. Zeki, Semir Cereb Cortex Articles Perception entails interactions between activated brain visual areas and the records of previous sensations, allowing for processes like figure–ground segregation and object recognition. The aim of this study was to characterize top-down effects that originate in the visual cortex and that are involved in the generation and perception of form. We performed a functional magnetic resonance imaging experiment, where subjects viewed 3 groups of stimuli comprising oriented lines with different levels of recognizable high-order structure (none, collinearity, and meaning). Our results showed that recognizable stimuli cause larger activations in anterior visual and frontal areas. In contrast, when stimuli are random or unrecognizable, activations are greater in posterior visual areas, following a hierarchical organization where areas V1/V2 were less active with “collinearity” and the middle occipital cortex was less active with “meaning.” An effective connectivity analysis using dynamic causal modeling showed that high-order visual form engages higher visual areas that generate top-down signals, from multiple levels of the visual hierarchy. These results are consistent with a model in which if a stimulus has recognizable attributes, such as collinearity and meaning, the areas specialized for processing these attributes send top-down messages to the lower levels to facilitate more efficient encoding of visual form. Oxford University Press 2011-03 2010-07-09 /pmc/articles/PMC3041008/ /pubmed/20621984 http://dx.doi.org/10.1093/cercor/bhq122 Text en © The Author 2010. Published by Oxford University Press. http://creativecommons.org/licenses/by-nc/3.0 This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0), which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. |
spellingShingle | Articles Cardin, Velia Friston, Karl J. Zeki, Semir Top-down Modulations in the Visual Form Pathway Revealed with Dynamic Causal Modeling |
title | Top-down Modulations in the Visual Form Pathway Revealed with Dynamic Causal Modeling |
title_full | Top-down Modulations in the Visual Form Pathway Revealed with Dynamic Causal Modeling |
title_fullStr | Top-down Modulations in the Visual Form Pathway Revealed with Dynamic Causal Modeling |
title_full_unstemmed | Top-down Modulations in the Visual Form Pathway Revealed with Dynamic Causal Modeling |
title_short | Top-down Modulations in the Visual Form Pathway Revealed with Dynamic Causal Modeling |
title_sort | top-down modulations in the visual form pathway revealed with dynamic causal modeling |
topic | Articles |
url | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3041008/ https://www.ncbi.nlm.nih.gov/pubmed/20621984 http://dx.doi.org/10.1093/cercor/bhq122 |
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