How the Brain 'Reboots' Itself After Being Impacted by Anesthesia

Anesthesia can completely disable patients, rendering them unresponsive during surgery. Yet hours later, they will wake up with their memories and skills intact. Now, scientists have found out how our brains reboot themselves after being impacted by anesthesia, revealing how brains navigate from unconsciousness back to consciousness.

Previous research has shown that the anesthetized brain is not "silent" under surgical levels of anesthesia. Instead, it experiences certain patterns of activity, and it spontaneously changes these patterns over time.

In order to get a better view of how the brain responds to anesthesia, the researchers recorded the electrical activity from several brain areas associated with arousal and consciousness in a rodent model that had been given the anesthetic isoflurane. The scientists then slowly decreased the amount of anesthesia given to the rodent and monitored how the electrical activity changed.

So what did they find? It turns out that the brain activity occurred in discrete clumps, or clusters, and that the brain did not jump between all of the clusters uniformly. In addition, a small number of activity patterns consistently occurred in the anesthetized rodents and the patterns depended on how much anesthesia the rodent was receiving. In fact, the brain would jump spontaneously from one activity pattern to another.

"Recovery from anesthesia is not simply the result of the anesthetic 'wearing off,' but also of the brain finding its way back through a maze of possible activity states to those that allow conscious experience," said Andrew Hudson, one of the researchers, in a news release. "Put simply, the brain reboots itself."

The findings reveal how the brain copes with anesthesia. More specifically, the research could help physicians reexamine how they approach monitoring people under anesthesia in the operating room. Moving forward, the researchers hope to test other anesthetic agents to see if they produce similar characteristic brain activity patterns.

The findings are published in the journal Proceedings of the National Academy of Sciences.