Consciousness and the archipelago of functional integration: On the relation between the midbrain and the ascending reticular activating system

Historically, the relation between consciousness and the brainstem has been demonstrated, on the one hand, by injuries to the upper brainstem that lead to minimum states of consciousness, comas and persistent vegetative states and, on the other hand, by electrophyisiological recordings that link the ascending reticular activating system (ARAS) with vigilance and attention, functions which are necessary for interpersonal relationships. With the advances made in the clarification of the connections between the brainstem and other regions of the brain there has been no corresponding conceptual revision of the functional context within which the ARAS performs its role of activation and way in which it activates the cerebral cortex, unlike other structures of the brain. In this paper we shall discuss the way in which the brainstem—(a) fundamental terminal of multiple ascending neural pathways—influences and modulates cortical activities; (b) the context of which the ARAS is a fundamental part—the centroencephalic archipelago of functional integration—for the transmission of contents to specific regions that generate the sensation of subjectivity.