Can a ‘brain in a vat’ be conscious?

image via New Scientist

January 20, 2026, 12:00 PM

• •Hemispherotomy patients have one brain hemisphere disconnected from the rest.
• •Isolated hemispheres show intact brain networks but enter a deep sleep-like state.
• •Slow brain waves suggest diminished or absent consciousness in the isolated hemisphere.
• •The findings raise questions about the requirements for consciousness and its relationship to external stimuli.

Researchers studying hemispherotomy patients, who have had one brain hemisphere disconnected, are exploring the nature of consciousness. Studies show that the isolated hemisphere's brain networks remain surprisingly intact, but it enters a state resembling deep sleep. This suggests that consciousness may be diminished or absent in the disconnected hemisphere, challenging the idea of an 'island of awareness.' The research highlights the importance of brain waves and the potential role of external stimuli in maintaining consciousness.

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