Dynamic Neural Correlates Of Consciousness As A Function Of The Level Of Processing.

Research project objectives/Hypothesis Consciousness remains one of the most challenging topics in the cognitive neuroscience. Which brain network subtends a conscious experience and how it does that? A lot of studies looked for the neural correlates of consciousness using a range of different stimuli and tasks, leading to strongly contradictory conclusions. According to one leading theory, the Recurrent Processing Hypothesis (RPH), higher and lower visual regions involved in increasing recurrent interactions subtend a gradual increase of awareness of stimuli (Lamme, 2010). As a result, stimuli gradually become more visible the more information about them is being accumulated. The other approach, Global Workspace Theory, proposes that conscious visual perception is dichotomous, and related to the sudden synchronous activation of parieto-frontal and posterior cortical regions (compared to “ignition”) at the moment the stimulus becomes visible (Dehaene et al. 2006). In an earlier work, based on the observation that existing evidence for both approaches appear to be based on different types of tasks and stimuli, we have already shown that by taking the level of processing of stimuli into account (for example low level features of visual stimuli and simple tasks versus high level features of stimuli and semantic tasks), one can integrate contradictory results and theories in the domain of consciousness. The aim of the present project is to provide a new empirical evidence for this approach on a level of neural activity measured by fMRI technique.

Research methodology The planned experiments will be based on the paradigm used by Windey et al. (submitted). This paradigm allows for manipulating task factor while keeping the stimulus factor constant, thus allowing for a testing effects of task and stimulus visibility and subject perceptual confidence. In Experiment 1 we plan to use stimuli used in the Windey et al. study and in Experiment 2 - another type of stimuli, in order to corroborate the original finding. To measure brain activity associated with the task we plan to use event-related fMRI technique, which allows for estimating BOLD responses to individual trials. This approach allows us to correlate activation of single regions and networks with subjective data (stimulus visibility changes and confidence measures).

Research project impact Our project aims to contribute to the research field of consciousness studies by trying to integrate two apparently divergent theories of the neural correlate of consciousness. If our hypotheses will be confirmed it will provide evidence that conscious processing of visual input is strongly dependent on what is the purpose of this processing, thus underscoring the flexibility of the “organ of thought”. In case the results will not be in accordance with our prediction, they will probably provide strong support for one of the alternate theories of NCC. On a societal level, research aiming at explaining the neural mechanism of consciousness is important for medicine, since it provides an evidence-based concept for a diagnosis of consciousness in severe disorders of brain function.