A theory of consciousness
Consciousness is the subjective awareness of momentary experience interpreted in the context of personal memory and present state. I propose that two brain systems converge to create consciousness. The exogenous system sends information about multimodal external stimuli to basal dendrites in widely dispersed pyramidal cell ensembles in the cortex of the brain; this system produces synchronized fragments of sensations. The endogenous system distributes readout of representations of memories, activated in systems established by associative learning, diffusely to apical dendrites. Convergence of exogenous and endogenous inputs enhances cellular excitability, and fragmented sensations are thereby converted to fragments of perception. Local field potentials periodically modulate all cortical membrane potentials and facilitate synchronous discharge of these excited elements. Feedback between the cortex and the thalamus results in a cortico-thalamo-cortical reverberation, binding the fragments into a unified global percept. Sustained reverberation produces a resonating electromagnetic field of synchronized elements. The momentary content of information in the brain is this distributed coherence, which is negative entropy. Consciousness is a physical property of this field, producing the subjective awareness of this information.