Conative regulation of cortical activity by the reticular formation, hypothalamus, and thalamus.

Evolution of neural regions suggests the requirement for a common format for information units exchanged among regions. Short-term memory experiments suggest a format of six or seven items. A similar number of configurations of primary cerebral interactions is proposed, associated with arousal, sleep, approach, withdrawal, perseveration, alert scanning, and commanded by the reticular formation. A comparable number of basic states (feeding, mating, grooming, shelter-seeking, fighting, etc.) is proposed as operating within these configurations, under regulation by the hypothalamus. Conative variables from this region are transformed into patterns of regulation for local cortical populations by the thalamus. Elaboration of these configurations and states by higher structures leads to new forms of cortical activity only loosely coupled to brain stem systems.