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Time:2019-06-03

Research reveals how our brains become conscious and lose it

Drug-induced loss of consciousness (mLOC) during anesthesia is associated with disruption of the brain's anatomical macroscopic connections (trans-cortical regions), but the role of brain microcircuits in LOC remains unclear. How does our brain produce consciousness? Why do we lose it during anesthesia? Influential theories suggest that consciousness relies on the brain's ability to distinguish between a particular sensory input and a large number of alternatives, akin to being able to choose from many outcomes.

In fact, several studies using fMRI in humans have identified a range of resting states of rich cortical activity at the macroscopic anatomical scale, at the large brain region level. However, according to a research team led by Columbia University, a person's ability to identify a set of alternatives at all times should come from microscopic patterns of activity, or microstates, at the level of local neurons as a whole (the functional building blocks of neural circuits).

Researchers at Rafael Yuste's lab at Columbia University have for the first time used cellular resolution two-photon calcium imaging in mice to study local changes in the microstate of neurons during anesthesia. The team found that anesthesia disrupted the number of neural patterns by reducing the network microstates of the cerebral cortex and the neuronal ensemble, confirming their findings in microelectrode array recordings of the two subjects.

Their results, published recently in Cell Systems, suggest that during mLOC, the brain's functional connections are disrupted at both the microscopic and the macroscopic anatomical scales. Rafael Yuste, professor of biological sciences and neuroscience and director of the Yuste laboratory at Columbia University, said: "this study is important because it brings the nature of consciousness to the level of neural circuits. "It provides a clue to how changes in the coordination of small groups of neurons caused by pathology or anesthetics can lead to changes in consciousness." Yuste is also a member of the data science institute at Columbia University and one of the founders of the brain project.

A mainstream view is that although mLOC destruction connected to the function of macro, but local network is still in the display is similar to the waking state dynamic, but on an isolated way, first author Michael Wenzel said: "although this suggests that the LOC is caused by neural activity in each region of the brain not harmonious, but we found that in the process of mLOC, significant changes have taken place in the local network dynamically. Our results suggest that the loss of consciousness may be due to changes in local microcircuits, which create defects in macroscopic connections." He was then an associate researcher in Rafael Yuste's lab.

The study, entitled "Reduced Repertoire of Cortical Microstates and Neuronal Ensembles in Medically Induced Loss of Consciousness", to understand the local neurons in dynamic how to lead to a Loss of Consciousness or provides the basis.

The authors note that while they hope their research will help the basic science of neural circuits, the mechanism by which local circuits play a role in loss or gain of consciousness remains challenging.

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