The explanatory gap in Neuroscience

Introduction We all know what it is like to be conscious, to be aware of something, to be aware of ourselves. However, even though there is this consensus and even though most would agree that consciousness is intimately related to brain functions, a universally accepted definition is still lacking. It is one of the goals of cognitive neuroscience to arrive at a better characterization of consciousness through a better understanding of the underlying neuronal mechanisms – and there have been remarkable advances in the study of the Neuronal Correlates of Consciousness (NCC). Since the seminal paper of Crick and Koch (1990), several theoretical proposals (Dehaene, Changeux, Naccache, Sackur, & Sergent, 2006; Lamme, 2006; Singer, 2000) as well as important empirical contributions regarding NCC have been made. However, important questions remain unresolved. In the following we propose that the search for a neuronal correlate of consciousness is equivalent with the search for neuronal mechanisms that have to account for several constitutive properties of consciousness. Therefore, we shall first summarize these characteristics and then explore putative mechanisms. Based on theoretical considerations and empirical evidence we propose that neuronal synchrony between distant neuronal assemblies might be a key mechanism for perceptual awareness. Finally, some pressing questions in the field of consciousness research will be discussed.