Neural complexity in the functional and dysfunctional brain: some tests of the dynamic core hypothesis
Although functional connectivity between different brain regions is often presumed to be a necessary prerequisite for the emergence of consciousness, functional connectivity is not unique to conscious states. How, therefore, can conscious and unconscious states be differentiated on this basis? One answer, provided by Edelman and Tononi\'s ‘Dynamic Core Hypothesis’, is that functional connectivity is insufficient to sustain consciousness: what is required is a specific pattern of connectivity involving high levels of both integration and differentiation called ‘Neural Complexity’. Conscious processes can be distinguished from non conscious process in that they are associated with higher levels of neural complexity. Here I report a series of studies designed to test the predictions of the Dynamic Core Hypothesis using experimental paradigms in which the participants experience a spontaneous shift in the state of conscious awareness whilst Neural Complexity was measured from the pattern of functional connectivity in the ongoing EEG. Although the results obtained were broadly consistent with the Dynamic Core Hypothesis, the theory suffers from some critical ambiguities and there are significant practical difficulties in testing it adequately. Despite these caveats, I argue that the Dynamic Core Hypothesis has made an important contribution to our understanding of the type of functional organisation that is required for consciousness to emerge and represents a good starting point in the search for a neural correlate of consciousness.