Anesthetics can greatly divert the propagation of brain waves

Imagine that the conscious brain is like an ocean wave, tumbling in the collision and dispersion of waves of different sizes and shapes, whirling and flowing in many different directions

More bluntly, research published in the Journal of Cognitive Neuroscience by scientists at MIT's Picower Institute for Learning and Memory shows that propofol essentially changes how brain waves of different frequencies appear on the surface of the brain.

Traveling waves are thought to have many important functions because they coordinate the activity of brain cells in the areas of the brain they cover

"Propofol dramatically alters the rhythms we associate with higher cognition," Miller said

Co-senior author Emory N.

"The traveling waves produced by propofol help us realize that many of the dynamic phenomena produced by anesthetics can alter arousal, such as unconsciousness,

The study's lead author Sayak Bhattacharya, a Picower postdoctoral researcher in Miller's lab, reanalyzed a dataset of two animals after receiving propofol anesthesia, where they remained in this state for a period of time and then recovered awareness

"In the same experiment, no study has looked at how traveling waves go from awake to anesthetized and then directly back to awake," he said

The lab published its first analysis of the dataset in 2021, documenting a profound shift towards delta waves, but not measuring the propagating properties of the waves

In the new analysis, Bhattacharya and his co-authors found significant changes, not only in frequency, but also in the direction, velocity, structural organization, and planar and rotational forms of the waves

"Slow frequency delta (~1Hz) waves increased, while high frequency (8-30Hz) waves decreased," the authors write

After the animals regained consciousness, their waveforms all returned to their pre-propofol-treatment levels

"We speculate that the dramatic breakdown of beta waves and their orientation may lead to loss of consciousness under propofol anesthesia," he said

Notably, the findings of this study suggest an important distinction between anesthesia and sleep (a common misconception that the two states of unconsciousness are similar)

article title

Propofol anesthesia alters cortical traveling waves