Amazing stuff!
"... anesthesia. It’s great for eliminating the perception of pain—but with brain activity significantly suppressed ... Scientists wanted to better understand what the anesthetized brain is actually doing—and whether it more closely mimics sleeping or a coma.
Researchers recorded whole-head electroencephalograms (EEGs) for 28 patients under anesthesia, 14 patients who were resting but awake, 20 patients in REM sleep, and 40 comatose patients.
They found that, at different frequencies, the brain waves of anesthetized patients shared properties of both sleep and comas. Brains in REM sleep, in particular, overlapped heavily with those under anesthesia. But there were brain waves unique to anesthesia, too, leading the authors to conclude it is indeed its own state of neural activity. ..."
From the significance and abstract:
"Significance
Every day, thousands of patients undergo general anesthesia, a safe and reversible medically induced state of unconsciousness often likened to sleep or coma.
Despite profoundly altering brain function, most procedures are carried out without monitoring the brain due to limited understanding of optimal tracking methods.
Here, we demonstrate that whole-head scalp electroencephalography can precisely map brain states during anesthesia showing both elements of sleep- and coma-like states. We identify distinct neural activity patterns unique to anesthesia that could enhance intraoperative neuromonitoring. Moreover, our findings open up future avenues of investigating neural activity during anesthesia, potentially steering it closer toward sleep instead of coma thus promoting better cognitive outcomes and postoperative recovery.
Abstract
General anesthesia is often compared to sleep but may more closely resemble a medically induced coma. While all three states involve a loss of awareness, the extent of their neural similarity remains unclear.
Electrophysiological markers, such as delta activity (< 4 Hz), are present in slow wave sleep, disorders of consciousness (DoC, including coma), and propofol anesthesia but are absent during rapid eye movement (REM) sleep.
Frontal alpha oscillations are a key feature of propofol anesthesia and detectable via intraoperative EEG.
However, it remains unclear whether alpha and delta activity fully define the brain state.
Using whole-head EEG, we analyzed brain activity in individuals under propofol anesthesia, during sleep, or in DoC in the intensive care unit.
Our spectral parameterization and similarity analyses revealed that propofol anesthesia exhibits spatiotemporal patterns resembling both coma and sleep. We introduced a spectral orthogonalization approach, identifying unique signatures of propofol anesthesia, including posterior slow waves, frontocentral delta, and reduced aperiodic activity.
Critically, the reduction in aperiodic activity partially overlaps with REM sleep and may reflect decreased cortical excitability, contributing to reduced arousal, muscle atonia, and immobility common to both states.
These results imply that propofol anesthesia creates a brain state where some features resemble sleep while others are more similar to coma.
Embracing its full spatiotemporal complexity could improve titration of sedation, thus minimizing excessive suppression and the risk of postoperative cognitive deficits."
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