Putting the puzzle together. Part II: towards a general theory of the neural correlates of consciousness

Part I of this two-part paper (Newman, 1997) provided a broad overview of clinical and experimental findings bearing on the neural correlates of conscious processes. It was argued that several neurocognitive models related to: orienting to the outer world, dream (REM) sleep, and the integration of sensory-motor representations, converge upon a core ‘conscious system’, dubbed the extended reticular-thalamic activating system (ERTAS). The functions of the ERTAS, which shares extensive projections with the cerebral cortex, are mostly ‘implicit’, in contrast to the explicit representation of conscious content within the neocortex. Part II expands this ERTAS model to encompass: the generation of coherent patterns of EEG activation, the integration of distributed cortical processes into a stream of unified percepts (binding), and selective attention, as well as links between the ERTAS and systems providing the neural substrates for episodic memory and volition.