Consciousness and the brainstem.

In the first part of this article we summarize a theoretical framework and a set of hypotheses aimed at accounting for consciousness in neurobiological terms. The basic form of consciousness, core consciousness is placed in the context of life regulation; it is seen as yet another level of biological processing aimed at ensuring the homeostatic balance of a living organism; and the representation of the current organism state within somato-sensing structures is seen as critical to its development. Core consciousness is conceived as the imaged relationship of the interaction between an object and the changed organism state it causes. In the second part of the article we discuss the functional neuroanatomy of nuclei in the brainstem reticular formation because they constitute the basic set of somato-sensing structures necessary for core consciousness and its core self to emerge. The close relationship between the mechanisms underlying cortical activation and the bioregulatory mechanisms outlined here is entirely compatible with the classical idea that the reticular formation modulates the electrophysiological activity of the cerebral cortex. However, in the perspective presented here, that modulation is placed in the setting of the organism's homeostatic regulation.