Unconsciousness caused by propofol has a similar metaphorical effect on high-frequency brainwaves

Under propofol general anesthesia, very slow frequency traveling wave conversion and dominance redirect and interfere with high-frequency traveling wave related to consciousness function.

Think of the conscious mind as an ocean, tumbling in the collision and dispersion of waves of different sizes and shapes, rotating and flowing in many different directions. Now imagine an ocean liner lumbering past, smoothing everything behind it with its powerful wake. A new study found that unconsciousness caused by propofol, a commonly used drug, has a similar metaphorical effect on high-frequency brainwaves. It seems to sweep high-frequency brainwaves aside. As an obvious result, consciousness will also be swept away.

More simply, a study published in the Journal of Cognitive Neuroscience by scientists from the Piccol Institute of Learning and Memory at MIT shows that propofol has greatly changed the different frequencies of brain waves propagating on the brain surface or cortex. The conscious brain shows mixed waves of various frequencies rotating in different directions or moving in a straight line, while the brain under propofol anesthesia is strong and very low frequency“ δ” Dominated by waves, such waves roll directly outward in the opposite direction, rather than slowly rotating around the center point as in the state of consciousness. At the same time, the higher frequency "beta" waves become less and the structure is more irregular, only along the δ Wave dominated direction of propagation.

Traveling waves are assumed to have many important functions because they coordinate the activities of brain cells in the areas covered by the brain. These methods include reading information from memory, storing it there, and waiting for use in cognition. They can also help perceive and act as a way of keeping time in the brain. Earl K. Miller, professor of neuroscience in the Department of Brain and Cognitive Sciences at MIT and senior author, said that these findings showed how anesthesia profoundly changed the brain state when inducing and maintaining unconsciousness.

"Propofol has dramatically altered our rhythm associated with advanced cognition," Miller said "I saw it when I was awake β Traveling waves are pushed aside, changed and become stronger by anesthesia δ Traveling wave redirection. The delta is like a bull in a porcelain shop. "

Emory N. Brown, co senior author, said that the research results showed that anesthetics can act on the brain in many ways.

"The traveling wave generated by propofol helps us realize that many dynamic phenomena generated by anesthetics can help change the arousal state, such as unconsciousness," said Brown, an anesthetist at Massachusetts General Hospital and Professor Edward Hood Taplin of MIT's Computational Neuroscience and Health Science and Technology. "Therefore, it is unreasonable to think that all anesthetics have a single mechanism of action."

The first author, Sayak Bhattacharya, is a Picower postdoctoral researcher in Miller's Laboratory. He led the study and reanalyzed the data set recorded from two propofol anesthetized animals. They stayed in this state for a period of time and then regained consciousness. Batacharia said that this was very important because although traveling waves were observed many times in anesthetized subjects, this study was one of the first studies to track traveling waves during the whole process of losing and recovering consciousness.

He said: "No research has observed how traveling waves directly changed from awake state to anesthetic state, and then returned to awake state in the same experiment." "We continuously monitor the behavior of these waves when animals are awake, their changes when they lose consciousness, and their changes when they recover consciousness - all of which are continuously tested in the same animals. This allows us to explore in real time how the neural pathway that generates sound waves is changed."

The first analysis of the data set by the laboratory was published in 2021, which recorded the profound transformation to delta waves, but did not measure the wave propagation properties.

In the new analysis, Batacharia and his co authors found that not only the frequency had changed significantly, but also the direction, velocity, structure and organization of waves, as well as the plane and rotation forms.

The author wrote: "Slow frequency δ The (~1 Hz) wave increases while the high-frequency (8-30 Hz) wave decreases. " "Slow triangular waves accelerate and become more spatially organized. They become more planar (less rotating), and the number of mirror waves propagating in the reverse direction increases. After losing consciousness, no matter which direction the slow triangular waves flow, they are dominant. High frequency waves weaken and lose their structure after losing consciousness, although they show enhanced (wave) strength, and give priority to slowing down δ The direction in which the waves flow less frequently. "

After the animals regained consciousness, their electric wave patterns returned to the state before taking propofol. Batacharia said that these two states (unrestrained before and after anesthesia β And during anesthesia δ The obvious connection between dominance) and state of consciousness strongly indicates the connection between them.

He said, "We assume that, β The violent decomposition and redirection of traveling waves may lead to loss of consciousness under propofol anesthesia. "

It is worth noting that the findings of this study indicate an important difference between anesthesia and sleep (a common misconception is that the two unconscious states are similar). During normal sleep, δ Waves propagate in a rotational manner, which may provide a time point and induce "peak time dependent plasticity", which is necessary to consolidate the memory of accumulated experiences during the day. However, under the action of propofol, δ Waves become flat instead of rotating, which destroys the mechanism of assisting memory and deprives the brain of its key function of sleep.

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