Parameter-based assessment of visual attention: functional neuroanatomy, timing and interference

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Understanding the mechanisms of visuo-spatial attention is of particular importance both from the perspective of basic visual neuroscience and from the perspective of clinical neurology; as the allocation of attention in space is a prerequisite for the effective interaction with our visual environment. The aim of this proposal is to provide further evidences of top-down and bottomup process by combining behavioural measures, functional magnetic resonance imaging (fMRI) and the analysis of effective connectivity. Based on a series of pilot experiments several hypotheses will be tested, according to the basic assumption that the focus of attention can be split if targets are distributed across hemifields. In an event-related parametric design we will analyze the correlation between behavioural measures (reaction times and error rates) and the hemodynamic response of early visual and parietal cortical areas. Our approach has several advantages, which go beyond previous work in the field; i) it allows a separate analysis of the cueing period and the target selection period and their related activation within each of the retinotopic regions of interest (ROIs), ii) varying the saliency of targets will allow us to examine task difficulty effects and their impact on the cueing period and the target selection period, iii) the analysis of the attentional modulation of connectivity between multiple ROIs will allow quantification of contextual modifications of neural interactions within early visual areas as well as between early visual areas and areas in parietal and frontal cortex.