A small amount of electricity delivered at a specific frequency to a particular point in the brain will snap a monkey out of even deep anesthesia, pointing to a circuit of brain activity key to consciousness and suggesting potential treatments for debilitating brain disorders.
Macaques put under with general anesthetic drugs commonly administered to human surgical patients, propofol and isoflurane, could be revived and alert within two or three seconds of applying low current, according to a study published today in the journal Neuron by a team led by University of Wisconsin-Madison brain researchers.
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. Then, within a few seconds of switching off the stimulation, their eyes closed again. The animal is right back into an unconscious state." Yuri Saalmann, UW-Madison psychology and neuroscience professor
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. But the new study is the first to pull primates in and out of a deep unconscious state, and the results isolate a particular loop of activity in the brain that is crucial to consciousness.
Saalmann's lab focused its attention 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 disruption like coma. But location alone was not enough to manipulate consciousness. Building on studies of waking versus unconscious brain activity in cats, says graduate student Michelle Redinbaugh, the researchers tried to match the frequency of central lateral thalamus activity during wakefulness.
Precisely stimulating multiple sites simultaneously as little as 200 millionths of a meter apart and applying bursts of electricity 50 times per second proved to work like a switch to bring the brain in and out of anesthesia. Related Stories
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