Raheleh Davoodi - Department of Biomedical Engineering Amirkabir University of Tech
Mohammad Hassan Moradi - Department of Biomedical Engineering Amirkabir University of Tech
Ali Yoonessi - School of Advanced Medical Technologies Tehran University of Medical Science

Background: While consciousness and top-down attention seem to be inextricably connected, recent evidence has suggested that these processes can be present in the absence of the other. Recent studies show that observers can pay attention to an invisible stimulus (unconscious), and that a stimulus can be clearly seen in the absence of attention. We used a novel psychophysics task to explore the neural correlates of top-down attention and consciousness. Method: The task is meant to confirm that these two processes are independent from one another. EEG were recorded during the task from 45 subjects in occipital, Parietal and frontal lobes. Target-locked ERPs for masked and unmasked condition were constructed. Time features corresponding to P100, ,200 and P300 components (i.e. correlate candidates of consciousness and attention) were extracted for all eight channels separately. Results: The results indicate that some of the mentioned components are increased when attention or consciousness occurs. By comparing difference waves in each condition separably, we found that increase in positivity in P100 window is the only ERP correlate of consciousness and decrease in negativity in ,100- ,200 window and increase in positivity in P300 window are ERP correlates of attention in O1, O2, PO7 and PO8 which are relevant channels. Conclusions: Our task could separate attention and consciousness successfully through their neural correlates. Our results introduce new ERP correlates of attention and consciousness. The results also suggest that these ERP components are meaningful features for the distinction between these two concepts. To our knowledge, this is the first time that these correlates of consciousness and specially attention are introduced in separable method.

attention; consciousness; ERP; psychophysics