The Dynamics of the Unconscious Brain Under General Anesthesia

March 22, 2017
Emery Brown

MBB Distinguished Harvard Lecture

Emery Brown, M.D., Ph.D.

4:00 PM, March 22, 2017

Pound 101, 1563 Massachusetts Avenue


General anesthesia is a drug-induced, reversible condition comprised of five behavioral states: unconsciousness, amnesia (loss of memory), analgesia (loss of pain sensation), akinesia (immobility), and hemodynamic stability with control of the stress response. Our work shows that a primary mechanism through which anesthetics create these altered states of arousal is by initiating and maintaining highly structured oscillations. These oscillations impair communication among brain regions. We illustrate this effect by presenting findings from our human studies of general anesthesia using high-density EEG recordings and intracranial recordings. These studies have allowed us to give a detailed characterization of the neurophysiology of loss and recovery of consciousness due to propofol. We show how these dynamics change systematically with different anesthetic classes and with age. We present a neuro-metabolic model of burst suppression, the profound state of brain inactivation seen in deep states of general anesthesia. We use our characterization of burst suppression to implement a closed-loop anesthesia delivery system for control of a medically-induced coma. Finally, we demonstrate that the state of general anesthesia can be rapidly reversed by activating specific brain circuits. The success of our research has depended critically on tight coupling of experiments, signal processing research and mathematical modeling.


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