Scientists Switch Consciousness On Or Off In Monkeys Using Tiny Brain Zaps


Tom Hale


Tom Hale

Senior Journalist

Tom is a writer in London with a Master's degree in Journalism whose editorial work covers anything from health and the environment to technology and archaeology.

Senior Journalist


Zap me up, before you go, go. create jobs 51/Shutterstock

How’s this for a wake-up call? Scientists have shown that it's possible to instantly jolt a monkey out of deep anesthetized sleep using a quick zap of electricity to a small chamber found deep inside the brain. 

While it might just sound like a cruel method of torture, the discovery has provided some key insights into the nature of consciousness and it could help to develop better treatments for brain disorders.


The brain structure in question is known as the central lateral thalamus, a bundle of grey matter found just above the brainstem. Reported in the journal Neuron, researchers led by the University of Wisconsin–Madison found that stimulating this structure with electricity at a specific frequency was able to wake up a macaque monkey that had been dosed on general anesthetic drugs. Within seconds, the macaque snapped back into consciousness with totally normal brain function. However, the moment the electrical stimulation stopped, the monkey would fall unconscious once again.

“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,” Yuri Saalmann, UW–Madison psychology and neuroscience professor, said in a statement. “Then, within a few seconds of switching off the stimulation, their eyes closed again. The animal is right back into an unconscious state.”

This procedure has to be incredibly precise, however. Specific sites just 200 millionths of a meter apart have to be simultaneously shocked with electricity at a frequency of 50 Hertz in sharp bursts that repeat 50 times per second. If these exact conditions aren’t met, then no dice.

The researchers have dubbed this area as the “engine of consciousness.” Through understanding this engine, the team hopes to understand the physical process that underpins consciousness. Using brain scans while the monkeys moved from unconscious to conscious states, the researchers saw the central lateral thalamus stimulating parts of the cortex, which in turn told the central lateral thalamus to keep it "awake."


“So, you have this loop between the deeper layers of the cortex and the central lateral thalamus, which in a sense acts like an engine,” added Saalmann. “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.”

This knowledge could be used to help treat brain disorders that affect consciousness. We already know that damage to the central lateral thalamus is linked to disorders of consciousness, but the team also suggests a deeper understanding of the brain could perhaps be used to treat patients that are in a deep state of prolonged unconsciousness, such as a coma or a vegetative state.



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