Scientists discover brain mechanisms underlying fainting

A team of scientists from the University of Pennsylvania (USA) has established the exact moment of loss of consciousness through research on rats. Through anesthesia, they captured what was happening in different areas of the brain at that moment.

The researchers found that there are three areas in the brain that show temporary changes in activity at the moment of loss of consciousness that can interact with each other. Scientists also found out what role these areas play at the time of loss of consciousness, Medical Xpress reports.

According to study author Nanyin Zhang, neurologists generally understand what happens to a patient under anesthesia at the molecular level. But on a systemic level – that is, how different brain regions or neural circuits change their function in response to anesthetics and loss of consciousness – this has not been fully explored.

"Our study aimed to solve an unknown problem," the scientist explained.

To do this, the scientists combined two different methods: electrophysiological studies and functional magnetic resonance imaging (fMRI). By rapidly measuring electrophysiological signals (or electrical activity) in the brain over time, they determined the exact moment when the rat went from waking to unconscious.

They then overlaid this timestamped data on a map of whole-brain fMRI activity to examine different brain regions during this transition.

"We found that there are three areas in the brain that show temporal changes in activity at the time of unconsciousness: the medial prefrontal cortex, the hippocampus, and the thalamus. Although these areas have been associated with unconscious states in the existing scientific literature, our study is the first to show how they can interact with each other and what role they play at the time of unconsciousness," the scientists explain in an article published in the journal Advanced Science.

According to the researchers, previous work also did not indicate whether the activity in these three brain regions was the cause or effect of loss of consciousness. The results of the study by Zhang and his team suggest that loss of consciousness can be triggered by sequential events in these three parts, while increased activity in other parts of the cerebral cortex may be a consequence, not a cause, of loss of consciousness.

"Although the results were not unexpected, they provide new insight into the role of these brain areas in loss of consciousness," Zhang added.

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