The dynamical signature of conscious processing: From modality-specific percepts to complex episodes
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The search for neural correlates of human consciousness in past decades has been based on different assumptions and methods. Some researchers assume that conscious functions are localized in brain circuits, and ultimately pinned down to single neuron selective firing at the millisecond range, while others search for dynamic patterns, as the synchrony of neural potentials or slow waves in brain tissue. We raise and review evidence for the hypothesis that the composition of conscious processes has a dual dynamics: (a) Information processing carried by neuronal spike trains generating modality-specific contents and (b) the formation of complex episodes by dendritic fields synchronized in multiple frequencies and interacting with the astroglial calcium wave. On the basis of this evidence, we hypothesize an explanation for the coordination of the 2 types of processes: Oscillatory frequencies compose a multiplexing mechanism promoting the insertion of specific contents into a global hydroionic standing wave in brain tissue, which feeds back on dendritic fields, in a process that takes around 2 s to form 1 unitary conscious episode. A dynamical signature of conscious processing can be identified by means of a mathematical analysis of how the faster brain rhythms are nested in the slower ones.