Investigations of the global network properties of attention and awareness

Abstract

Attention and awareness are tightly coupled phenomena that describe how particular information is selected for processing and subsequently experienced. Many contemporary theories of both processes posit that there are specific neurobiological networks that produce each of these cognitive processes. These networks, however, do not exist in a vacuum and observable behavior is not the result of the activity of a single network. In order to fully understand how attention and awareness are instantiated in the brain, we must assess how connections between all networks of the brain differ for these phenomena. Network science and graph theory have taken hold in cognitive neuroscience as an instrument for describing both the global physical and functional connections in the brain. A primary goal of this thesis is to incorporate an understanding of the global changes in connectivity and network topology with current models of attention and awareness. Patterns of global functional integration were found to result from awareness of a simple target percept. These results support global neurobiological theories of awareness, rather than network-level or focal theories. However, the capture of attention by salient, irrelevant information produced an alternate global pattern of changes, favoring relatively more functional segregation. The results of these two experiments present potential mechanisms by which the brain processes task-relevant and task-irrelevant information, respectively. These mechanisms were then tested within the context of a single task, pitting processing of task-relevant information against potential distracting stimuli. Ultimately, by utilizing graph theory these experiments have identified global functional connectivity as a potential contributing brain mechanism of processing information.