Abstract

Consciousness-altering behaviour is, to a first approximation, a universal phenomenon; practically all human societies have experimented with altered states of consciousness in some form. In this article, we review the neuroscientific and psychological evidence in favour of the transient hypofrontality theory, a general brain mechanism that can account for a great number of phenomenological features shared by all ASCs. The theory is based on the conceptualization of brain areas and mental abilities into a functional hierarchy with the top layers in the prefrontal cortex contributing the most sophisticated elements of the conscious experience. Analogous to peeling an onion, the THT simply postulates that alteration to consciousness involves the progressive downregulation of brain networks supporting the highest cognitive capacities, down the functional hierarchy, one phenomenological subtraction at a time, to those supporting more basic ones. Accordingly, ASCs are principally due to a transient state of hypoactivity, of various depths and extent, in networks of the prefrontal cortex. Given the universality of ASCs, we ask why hypofrontality might have evolved.