It is time to combine the two main traditions in the research on the neural correlates of consciousness: C = L × D

Abstract

Research on neural correlates of consciousness has been conducted and carried out mostly from within two relatively autonomous paradigmatic traditions - studying the specific contents of conscious experience and their brain-process correlates and studying the level of consciousness. In the present paper we offer a theoretical integration suggesting that an emphasis has to be put on understanding the mechanisms of consciousness (and not a mere correlates) and in doing this, the two paradigmatic traditions must be combined. We argue that consciousness emerges as a result of interaction of brain mechanisms specialized for representing the specific contents of perception/cognition - the data - and mechanisms specialized for regulating the level of activity of whatever data the content-carrying specific mechanisms happen to represent. Each of these mechanisms are necessary because without the contents there is no conscious experience and without the required level of activity the processed contents remain unconscious. Together the two mechanisms, when activated up to a necessary degree each, provide conditions sufficient for conscious experience to emerge. This proposal is related to pertinent experimental evidence.

Keywords: consciousness; contents; excitatory postsynaptic potentials; level; neural correlates of consciousness; state; thalamus; visiual perception.

FIGURE 1

Three possible variants of L- and D-system presynaptic input to layer-5 pyramidal neurons that may determine contentful conscious experience. Variant (A) shows lack of sufficient acitivity for long-range integration and consciousness because D-system specific input to the perisomatic compartment of pyramidal neurons is weak or asynchronous with L-system presynaptic inputs to the neuron’s apical compartment. Variant (B) illustrates the opposite situation where the D-system presynaptic input is present but the L-system contribution is weak or incoincident. Both (A) and (B) represent scenarios lacking consciousness with its contents. In contrast, variant (C) illustrates sufficiently strong and synchronous presynaptic input from the D- and L-systems that leads to plateau-wave of activity and integration of the neuron’s contentful contribution to the phenomenal field of consciousness.