Brainwave phase shift as a marker of unconsciousness under anesthesia

• An easily measurable brain wave (EEG) phase shift may be a universal marker of unconsciousness under anesthesia.¹
• Different anesthetics produce unconsciousness by shifting brainwave phase, with the same electrophysiological result.^{1 1}

Gardner updates

• An easily measurable brain wave phase shift may be a universal marker of unconsciousness under anesthesia across different anesthetics. ¹

Weekly enrichment (2026-07-20)

• The underlying study, led by Alexandra Bardon with senior authors Earl K. Miller and Emery N. Brown at MIT’s Picower Institute, was published in Cell Reports in 2025 (volume 44, article 115685).^{2 3}
• Researchers recorded prefrontal cortex local field potentials in nonhuman primates under anesthetic doses of two drugs with very different molecular actions: ketamine (an NMDA-receptor antagonist) and dexmedetomidine (an alpha-2 adrenergic agonist).^{2 4}
• Despite their distinct mechanisms, both anesthetics converged on the same signature: after loss of consciousness, low-frequency phase locking increased across the recorded prefrontal regions.^{2 3}
• The direction of alignment depended on distance — within a hemisphere, activity in dorsolateral versus ventrolateral prefrontal subregions became more anti-phase (misaligned), while homologous regions across the two hemispheres became more in-phase (aligned).^{2 3}
• Even across the 2.5 mm span of a single electrode array, low-frequency waves shifted 20-30 degrees out of alignment, and across the roughly 20 mm between dorsolateral and ventrolateral arrays this implies an approximately 180-degree offset, consistent with large traveling waves sweeping across cortex.^{2 3}
• The interhemispheric increase in alignment reverses the pattern seen in the awake, cognitively engaged brain, where hemispheres are typically not well aligned, supporting phase realignment as a correlate of unconsciousness rather than mere power changes.^{2 4}
• The authors frame this readily measurable phase signature as a potential common, drug-agnostic marker of anesthetic-induced unconsciousness, useful for EEG-based depth-of-anesthesia monitoring and closed-loop systems that titrate dose to the patient’s state.^{2 4}

Footnotes

1. https://news.mit.edu/2025/unconsciousness-by-shifting-brainwave-phase-0605 ↩ ↩² ↩³ ↩⁴

2. https://doi.org/10.1016/j.celrep.2025.115685 ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷

3. https://www.biorxiv.org/content/10.1101/2024.03.20.585943v2 ↩ ↩² ↩³ ↩⁴

4. https://www.sciencedaily.com/releases/2025/05/250512105543.htm ↩ ↩² ↩³