Changes in functional connectivity support conscious object recognition

What are the brain mechanisms that mediate conscious object recognition? To investigate this question, it is essential to distinguish between brain processes that cause conscious recognition of a stimulus from other correlates of its sensoly processing. Previous fMRI studies have identified large-scale brain activity ranging from striate to high-level sensory and prefrontal regions associated with conscious visual perception or recognition. However, the possible role of changes in connectivity during conscious perception between these regions has only rarely been studied. Here, we used fMRI and connectivity analyses, together with 120 custom-generated, two-tone, Mooney images to directly assess whether conscious recognition of an object is accompanied by a dynamical change in the functional coupling between extrastriate cortex and prefrontal areas. We compared recognizing an object versus not recognizing it in 19 naive subjects using two different response modalities. We find that connectivity between the extrastriate cortex and the dorsolateral prefrontal cortex (DLPFC) increases when objects are consciously recognized. This interaction was independent of the response modality used to report conscious recognition. Furthermore, computing the difference in Granger causality between recognized and not recognized conditions reveals stronger feedforward connectivity than feedback connectivity when subjects recognized the objects. We suggest that frontal and visual brain regions are part of a functional network that supports conscious object recognition by changes in functional connectivity. (C) 2012 Elsevier Inc. All rights reserved.