# New Theory Locates Consciousness in the Brainstem, Not the Cortex Neuroscientists propose the brainstem acts as the primary seat of subjective conscious experience. - **Source:** [Earth.com](https://www.earth.com) - **Published:** 2026-11-05 - **Topic:** [science](https://brifing.si/c/science) - **Original article:** - **On Brifing:** https://brifing.si/s/81e23f32-6420-4c3b-9d6f-dfc7a2b2acfb ## Challenging Cortical Dominance Consciousness is traditionally associated with the cortex, the brain's outer layer responsible for complex cognitive processing. However, neuroscientists Marshall Devor and Mark Baron argue that the raw feeling of being conscious originates in the brainstem. This ancient structure at the base of the brain may hold the key to subjective awareness. ## The Pain Paradox Evidence suggests that stimulating the cortex during surgery rarely triggers pain, producing only flashes of light or tingling sensations. Even when the insula is stimulated, pain responses remain exceptionally rare. Conversely, cortical strokes often fail to eliminate pain, suggesting that the capacity for feeling resides outside the cortex's primary processing zones. ## Brainstem Damage and Coma Clinical observations show that small strokes within the brainstem can induce comas, whereas extensive cortical damage does not necessarily result in a loss of consciousness. Patients with hydrocephalus have also maintained full articulation despite significant cortical thinning. These findings support the theory that the brainstem is essential for maintaining a conscious state. ## Experimental Evidence in Rats Researchers injected anesthetics into rat brains 828 times to isolate consciousness-related regions. They discovered that targeting the mesopontine tegmentum induced unconsciousness within seconds. Larger lesions in this specific three-by-four-millimeter area consistently caused coma, mirroring clinical observations of human brainstem strokes and reinforcing the region's critical role in maintaining awareness. ## The Sentinel Model In this model, the cortex functions as a processor that identifies objects and evaluates survival threats. It sends this information to the brainstem, which acts as a sentinel. The brainstem circuit then determines which inputs enter conscious awareness, effectively marking specific streams of data as 'conscious' while the rest remains processed automatically. ## Evolutionary Perspective The authors suggest that the capacity for pain evolved early as an add-on to escape reflexes, long before the mammalian neocortex developed. By building upon the brainstem's existing machinery, the later evolution of the cortex utilized established neural pathways. This implies that consciousness may be a biological feature shared across many species. ## Limits of the Hypothesis While the brainstem theory provides a framework, it does not explain the exact mechanism by which neurons generate subjective experience. The authors acknowledge that hundreds of theories exist and none fully solve the 'hard problem' of consciousness. Their claim is limited to the biological location rather than the underlying physical mechanism. ## Future Research Directions The theory remains a hypothesis that requires further empirical validation. Future studies must investigate the mesopontine tegmentum and its axonal connections to the cortex and spinal cord. Determining whether specific neurons within this region transmit the signal that converts neural processing into subjective experience remains the primary challenge for neuroscientists today. ## Sources covering this story - https://www.earth.com/science/where-does-consciousness-begin-a-new-theory-points-deep-inside-the-brain/ — --- _Summary written by Brifing from the original reporting. Copyright in the original article belongs to its publisher; read the full piece at the link above._