Breakdown of the brain’s functional network modularity with awareness

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 112; no. 12; pp. 3799 - 3804
• Main Authors: Godwin, Douglass, Barry, Robert L., Marois, René
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences 24.03.2015; National Acad Sciences
• Subjects: Adolescent; Adult; Algorithms; Awareness; Behavior; Biological Sciences; brain; Brain Mapping - methods; Brain research; Consciousness; Female; Graph theory; Humans; Magnetic Resonance Imaging; Male; Models, Neurological; Models, Statistical; Nerve Net; Neurobiology; neurophysiology; Neurosciences; philosophy; psychology; Theoretical analysis; Young Adult; functional connectivity; awareness; consciousness; graph theory
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.1414466112

Significance How the brain begets conscious awareness has been one of the most fundamental and elusive problems in neuroscience, psychology, and philosophy. Correspondingly, this problem has spawned a remarkably large number of theories that differ by the proposed extent of cortical and subcortical changes associated with awareness, ranging from local to global changes in functional connectivity. Graph theoretical techniques, in combination with functional magnetic resonance imaging, provide a well-suited tool to adjudicate between these disparate theories by characterizing whole-brain patterns of communication. In this paper, we demonstrate large-scale differences in functional connections with awareness of a visual target, consistent with global models of awareness. Neurobiological theories of awareness propose divergent accounts of the spatial extent of brain changes that support conscious perception. Whereas focal theories posit mostly local regional changes, global theories propose that awareness emerges from the propagation of neural signals across a broad extent of sensory and association cortex. Here we tested the scalar extent of brain changes associated with awareness using graph theoretical analysis applied to functional connectivity data acquired at ultra-high field while subjects performed a simple masked target detection task. We found that awareness of a visual target is associated with a degradation of the modularity of the brain’s functional networks brought about by an increase in intermodular functional connectivity. These results provide compelling evidence that awareness is associated with truly global changes in the brain’s functional connectivity.