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Awareness and the neurocognitive mechanisms associated with it are still relatively poorly understood. In recent years, neuroscientists have highlighted brain structures involved in the process of consciousness without having full knowledge of them. Recently, neurobiologists have managed to wake up sleepy monkeys under anesthesia by electrically stimulating a particular area of their brain. These results have revealed key details about how consciousness works, and may offer new therapeutic avenues for brain disorders such as coma and vegetative states.
The brain structure in question is known as the central lateral thalamus, a bundle of gray matter found just above the brainstem. Researchers at the University of Wisconsin have found that stimulating this structure with electricity at a specific frequency can wake up a monkey that has been treated with general anesthetic drugs. Within seconds, the monkey returned to consciousness with completely normal brain function.
Ultra-precise electrical impulses to act on consciousness
However, the moment the electrical stimulation stopped, the monkey fell unconscious. "As long as you stimulate their brains, their behavior - full opening of the eyes, search for nearby objects, changes in vital signs, body movements and facial movements - and their brain activity, is that of a waking state" declares Yuri Saalmann, neuropsychologist. “Then, a few seconds after cutting off the stimulation, their eyes closed again. The animal was back in an unconscious state”. |
| By stimulating the central / ventral (red) nucleus of the thalamus via very precise electrical impulses, the researchers were able to manipulate the consciousness of the monkeys. Credits: Cédric Landmann |
This procedure must however be incredibly precise. Specific sites distant only 200 millionths of a meter must be simultaneously subjected to an electric shock at a frequency of 50 Hertz, in sudden gusts which are repeated 50 times per second. If these exact conditions are not met, then there is no alarm clock. The study was published in the journal Neuron
Understanding Consciousness Better To Treat Brain Disorders
Researchers have dubbed this area the "engine of consciousness." By understanding this engine, the team hopes to learn more about the physical process that underlies consciousness. Using brain scans while the monkeys went from unconscious to conscious, the researchers saw the central lateral thalamus stimulating certain areas of the cortex, which in turn suggested that the central lateral thalamus keep it awake.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 disturbances of consciousness, but the team also suggests that a deeper understanding of the brain could perhaps be used to treat patients who are in a deep state of prolonged unconsciousness, such as a coma or a vegetative state.
| Bibliography: Thalamus Modulates Consciousness via Layer-Specific Control of Cortex Michelle J. Redinbaugh, Jessica M. Phillips, Niranjan A. Kambi, Sounak Mohanta, Samantha Andryk, Gaven L. Dooley, Mohsen Afrasiabi, Aeyal Raz, Yuri B. Saalmann. Neuron, 2020; DOI: 10.1016/j.neuron.2020.01.005 |
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