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Where Bottom-up Meets Top-down: Neuronal Interactions during Perception and Imagery

Mechelli, Andrea ; Price, Cathy J. ; Friston, Karl J. ; Ishai, Alumit

In: Cerebral Cortex, 2004, vol. 14, no. 11, p. 1256-1265

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    Title
    • Where Bottom-up Meets Top-down: Neuronal Interactions during Perception and Imagery
    Author
    • Mechelli, Andrea. Wellcome Department of Imaging Neuroscience, Institute of Neurology, 12 Queen Square, London, WC1N 3BG, UK
    • Price, Cathy J.. Wellcome Department of Imaging Neuroscience, Institute of Neurology, 12 Queen Square, London, WC1N 3BG, UK
    • Friston, Karl J.. Wellcome Department of Imaging Neuroscience, Institute of Neurology, 12 Queen Square, London, WC1N 3BG, UK
    • Ishai, Alumit. Institute of Neuroradiology, University of Zurich, 8057 Zurich, Switzerland
    Document Type
    • Postprint
    Language
    • English
    Published in
    • Cerebral Cortex, 2004, vol. 14, no. 11, p. 1256-1265. Oxford University Press
    Other Version
    OAI-PMH Identifier
    • oai:doc.rero.ch:298997
    Summary
    Functional magnetic resonance imaging (fMRI) studies have identified category-selective regions in ventral occipito-temporal cortex that respond preferentially to faces and other objects. The extent to which these patterns of activation are modulated by bottom-up or top-down mechanisms is currently unknown. We combined fMRI and dynamic causal modelling to investigate neuronal interactions between occipito-temporal, parietal and frontal regions, during visual perception and visual imagery of faces, houses and chairs. Our results indicate that, during visual perception, category-selective patterns of activation in extrastriate cortex are mediated by content-sensitive forward connections from early visual areas. In contrast, during visual imagery, category-selective activation is mediated by content-sensitive backward connections from prefrontal cortex. Additionally, we report content-unrelated connectivity between parietal cortex and the category-selective regions, during both perception and imagery. Thus, our investigation revealed that neuronal interactions between occipito-temporal, parietal and frontal regions are task- and stimulus-dependent. Sensory representations of faces and objects are mediated by bottom-up mechanisms arising in early visual areas and top-down mechanisms arising in prefrontal cortex, during perception and imagery respectively. Additionally non-selective, top-down processes, originating in superior parietal areas, contribute to the generation of mental images, regardless of their content, and their maintenance in the ‘mind's eye'