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Title: Visual awareness and the brain
Author: Hon, N. H. H.
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 2005
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This thesis details an investigation into the neural correlates of visual awareness. Extant data acquired with whole brain imaging techniques suggest that being visually aware is associated with a widespread pattern of neural activity that includes the activation of frontal and parietal areas in addition to more specialised local processors (i.e. brain areas that process for specific sorts of information). However, this idea could not be unequivocally accepted because the relevant studies failed to control for or minimise the influence of attentional shifts and/or cognitive demands, two variables that have been known to engage frontal and parietal areas similar to those observed in studies of awareness. As such, it was initially impossible to determine whether the observed frontal and parietal activity was associated with awareness per se or instead with related but distinct processes. Here, in a series of functional magnetic resonance imaging experiments, the natural correlates of visual awareness were probed by manipulating the focus of attention. Behavioural studies have demonstrated that information not given the benefit of attentional processing is not available to conscious awareness. In the main experiments here, subjects viewed two streams of continuous (and equivalent) visual events, paying attention to only one stream and ignoring the other. Behavioural tests conducted confirmed that attended visual information was seen and remembered better than unattended information. Correspondingly, contrasting the neural activity associated with attended visual events with that associated with unattended visual events revealed a large-scale distributed pattern of neural activity (that included frontal and parietal foci), even when the influence of cognitive demands and spatial shifts of attention were controlled for or minimised. This pattern of activity was observed under different experimental conditions and with different stimulus sets, hinting at its generality. Further experiments ruled out the possibility that these results were due to novelty detection or inhibitory processes that operate when having to deal with multi-object visual displays. Additionally, it was found that these frontal and parietal areas where likewise sensitive to increases in cognitive demand, suggesting a strong link between awareness and problem solving. These findings are discussed and evaluated with reference to the notion of a global workspace that is proposed to support conscious, adaptive control of thought and behaviour.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available