Close your eyes and plug your ears: the outside world disappears, yet the feeling of "I am here" does not go anywhere. It is precisely this basic sense of one's own presence that the neuroscientists Marshall Devor of the Hebrew University of Jerusalem and Mark Baron of Beth Israel Deaconess Hospital and Harvard Medical School propose to look for not in the cerebral cortex, but in one of the most ancient parts of the brain — the brainstem.
Since the reign of the corticocentric view, the cortex has been regarded as the "registered address" of consciousness: it is here that sensory signals are processed, thoughts are born and perception is formed. However, in a theoretical article published in the journal The Neuroscientist in 2026, Devor and Baron point to facts that this picture explains poorly. Pain, unlike vision or hearing, has no dedicated cortical zone, and electrical stimulation of the cortex rarely produces painful sensations. On the other hand, small strokes in certain areas of the brainstem often plunge a person into a coma. There is also the opposite example: adults with hydrocephalus whose cortex was severely thinned retained full speech.
The authors draw key evidence from experiments on rats. Microscopic doses of an anesthetic injected into a tiny area of the upper brainstem — the mesopontine tegmentum — rapidly and reversibly switched off responses to pain and other signs of wakefulness. Such an experiment was carried out back in 2001 under the leadership of the article's first author. An important argument is also provided by children with hydranencephaly — a rare condition in which the cerebral hemispheres are destroyed in utero and replaced by fluid. Such children often have almost no cortex left, yet they smile, laugh, cry and respond to loved ones. The authors believe that these observations indicate that the brainstem provides a basic "feeling of presence," while the cortex merely fills it with content. The idea of consciousness without a cortex was also developed by Bjorn Merker, who had earlier spoken of consciousness in such children.
The hypothesis directly challenges corticocentric theories, such as global workspace theory and integrated information theory, which link consciousness to the widespread propagation of signals across the cortex. Devor himself, with co-authors, in an article for the journal Behavioral and Brain Sciences in 2022, criticized integrated information for relying on thalamocortical interactions. If basic consciousness arises in an ancient structure shared by all vertebrates, the minimal substrate of subjective experience may exist without complex cortical computations. This does not negate the role of the cortex in complex forms of awareness, but it calls into question its necessity for the very fact of having experience. The distinction here is important: detecting a harmful stimulus and feeling pain are different things. The nervous system can trigger an automatic withdrawal of the hand, but pain adds to this the experience: "I am in pain."
Imagine an automobile. The engine and basic electrics give the car the very ability to drive, while the dashboard and navigator show the route and make the trip meaningful. Without the engine, the dashboard is a useless set of lights, but without the dashboard the car still drives. According to the authors' version, the brainstem is responsible for consciousness being "switched on," and the cortex for its content.
It is important to understand: this is a hypothesis, not a proven mechanism. Devor and Baron themselves acknowledge that none of the hundreds of existing theories of consciousness, including their own, explains how neurons generate subjective experience. The hypothesis rests on indirect data: clinical cases, animal experiments and anatomical observations. Therefore, direct tests are needed, first of all the study of the midbrain itself and its connections. The authors also suggest that brainstem neurons may influence one another not through point contacts, but by releasing chemical substances that spread through surrounding tissues — roughly the way dopamine acts in certain parts of the brain.
If the minimal conditions of consciousness really lie in the brainstem, the boundary between "conscious" and "reflexive" behavior in vertebrates will become even more blurred. This also applies to medicine: doctors will have to assess the condition of patients with brain injuries more precisely, because external signs of wakefulness or their absence can be misleading.
