And that’s a good thing.

Millions of surgical procedures are performed every year. But many of these would not be possible without the aid of anesthesia; the miraculous medical ability to temporarily disable consciousness in a reversible and controllable manner. Despite the widespread use of anesthetics, we still don’t understand exactly how they work. And so researchers decided in a new study study the effect of anesthesia on the brain.

Fundamental questions

The research team sought to answer several fundamental questions with the study. For example, how does the brain ‘restart’ after a deep anaesthetic? Do brain functions all come ‘online’ at the same time or does it happen more gradually? And if so, which features will return first? “How the brain recovers from unconsciousness is clinically important,” said study researcher George Mashour. “At the same time, it also gives us insight into the neural basis of consciousness.”


In the study, the researchers collected 30 healthy adults who were put under anesthesia for three hours. Brain activity was then measured by electroencephalography (EEG). Just before and just after the participants set sail, they had to take cognitive tests. These tests measured reaction speed, memory and a few other skills, among other things.

One by one

The researchers make an interesting discovery. For the restoration of consciousness and cognition appears to be a process that unfolds over time. It means that not all brain functions go ‘online’ at the same time when you come out of anesthesia; that happens one by one.

Be the first online

Which brain function does it first again? Quite a surprising one, as it turns out. To the researchers’ surprise, they found that the abstract, problem-solving abilities, controlled by the prefrontal cortex, functioned fastest again. Other functions, such as reaction time and attention, take longer to recover. “Although surprising at first, it makes evolutionary sense that higher cognition should recover early,” said researcher Max Kelz. “For example, if someone is awakened by an alarming threat, the functions of the prefrontal cortex are important for positioning the situation and coming up with a plan of action.”

A comparison with a control group showed that it took about three hours for those who had been under anesthesia to make a full recovery. In addition, their sleep patterns did not appear to be affected in the days following the experiment. “This suggests that the healthy human brain is resilient,” study researcher Michael Avidan concluded. “Even after prolonged exposure to a deep anesthesia.”

Did you know…

…when you are under anesthesia, you have not completely lost your consciousness? For example, the brain still appears to process the words that are spoken in the environment. In addition, many people appear to dream while they are under anesthesia. And those dreams sometimes turned out to be mixed with reality. The research strongly suggests that general anesthesia is more like sleeping than thought. Read more here!