June 8, 2020

Is it possible for consciousness to be controlled through the brain? And if so, what implications could this have for people with serious brain disorders or conditions, like comas?

As it turns out, a small amount of electricity delivered at a specific frequency to a particular point in the brain will wake a nonhuman primate out of deep anesthesia, according to a study by a team led by researchers at the Wisconsin National Primate Research Center (WiNPRC) at the University of Wisconsin-Madison (UW).

Macaques put to sleep with general anesthetic drugs commonly administered to human surgical patients, propofol and isoflurane, were revived and alert within two or three seconds of applying a low electrical current.

“For as long as you’re stimulating their brain, their behavior — full eye opening, reaching for objects in their vicinity, vital sign changes, bodily movements and facial movements — and their brain activity is that of a waking state,” said Yuri Saalmann, UW-Madison psychology and neuroscience professor. “Then, within a few seconds of switching off the stimulation, their eyes closed again. The animal is right back into an unconscious state.”

Mice have been roused from light anesthesia before with a related method, and humans with severe disorders have improved through electric stimulation applied deep in their brains. The new study, however, is the first to pull primates in and out of a deep unconscious state.

In the study, the scientists focused on a spot deep in the core of the brain called the central lateral thalamus. Lesions in that area of the human brain are linked to severe consciousness disruptions, such as comas.

As the macaques moved from unconscious to conscious states, the researchers observed the central lateral thalamus stimulating parts of the cortex, or the outer folds of the brain. In turn, the cortex influenced the central lateral thalamus to keep it active, forming a loop—or an engine—of sorts.

Achieving this manipulation of consciousness in the brain required precisely stimulating multiple sites as little as 200 millionths of a meter apart simultaneously, as well as applying bursts of electricity 50 times per second. The researchers noted that designing and delivering electrical stimulation with such precision gives them hope that their approach could be used to help patients dealing with many types of abnormal brain activity.

 “We can now point to crucial parts of the brain that keep this engine running and drive changes in the cerebral cortex that affect your awareness, the richness of your conscious experience,” explained Saalmann.

The inner workings of the brain are complex and have yet to be fully unraveled, but scientists at the NPRCs are making daily progress in helping us to understand this fascinating and crucial organ. You can learn more about the other NPRC neuroscience studies here.


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