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Cerebral Cortex Advance Access originally published online on November 13, 2006
Cerebral Cortex 2007 17(9):2123-2133; doi:10.1093/cercor/bhl119
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© The Author 2006. Published by Oxford University Press. All rights reserved. For permissions, please e-mail: journals.permissions@oxfordjournals.org

Mechanisms of Top-Down Facilitation in Perception of Visual Objects Studied by fMRI

E Eger1,2, RN Henson1,3, J Driver1 and RJ Dolan2

1 UCL Institute of Cognitive Neuroscience & Department of Psychology, University College London, UK, 2 Wellcome Department of Imaging Neuroscience, University College London, UK, 3 MRC Cognition & Brain Sciences Unit, Cambridge, UK

Address correspondence to Dr Evelyn Eger, INSERM U.562, SHFJ-CEA, 4 place du General Leclerc, F-91401 Orsay Cedex, France. Email: eger{at}em.uni-frankfurt.de.

Prior knowledge regarding the possible identity of an object facilitates its recognition from a degraded visual input, though the underlying mechanisms are unclear. Previous work implicated ventral visual cortex but did not disambiguate whether activity-changes in these regions are causal to or merely reflect an effect of facilitated recognition. We used functional magnetic resonance imaging to study top-down influences on processing of gradually revealed objects, by preceding each object with a name that was congruent or incongruent with the object. Congruently primed objects were recognized earlier than incongruently primed, and this was paralleled by shifts in activation profiles for ventral visual, parietal, and prefrontal cortices. Prior to recognition, defined on a trial-by-trial basis, activity in ventral visual cortex rose gradually but equivalently for congruently and incongruently primed objects. In contrast, prerecognition activity was greater with congruent priming in lateral parietal, retrosplenial, and lateral prefrontal cortices, whereas functional coupling between parietal and ventral visual (and also left lateral prefrontal and parietal) cortices was enhanced in the same context. Thus, when controlling for recognition point and stimulus information, activity in ventral visual cortex mirrors recognition success, independent of condition. Facilitation by top-down cues involves lateral parietal cortex interacting with ventral visual areas, potentially explaining why parietal lesions can lead to deficits in recognizing degraded objects even in the context of top-down knowledge.

Key Words: fMRI • fusiform • object recognition • parietal • priming • top-down


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