American researchers have identified the brain mechanisms behind loss of consciousness due to anesthesia.
- Until now, how consciousness is lost in states, such as anesthesia, remains a mystery.
- A new study shows that upon loss of consciousness, three regions of the brain, the medial prefrontal cortex, hippocampus and thalamus, show transient changes in their activity.
- These results suggest that loss of consciousness may be triggered by sequential events in these three areas, while increases in activity in other cortical regions may be a consequence, rather than a cause, of loss of consciousness.
“During anesthesia, neuroscientists generally understand what happens to a patient at the molecular level. On the other hand, at the so-called systems level, that is, how different regions of the “The brain or neural circuits change their function in response to anesthetics and loss of consciousness remains a mystery.” This is what they said scientists from Pennsylvania State University (United States). In order to better understand this phenomenon, they decided to carry out a study published in the journal Advanced Science.
Anesthesia: transient changes in 3 brain regions at the time of loss of consciousness
The authors combined two different methods to determine the precise moment when rats went from an awake state to an unconscious state. Simultaneous recordings of electrophysiological signals in the anterior cingulate cortex and whole-brain functional magnetic resonance imaging (fMRI) were performed in rats exposed to a graded dose of propofol, an intravenous anesthetic agent. Then the team put the data together to map what’s happening in different regions of the brain at that time.
The results revealed that at the time of loss of consciousness, there is a strong increase in the low-frequency power of the electrophysiological signal. Furthermore, fMRI signals showed “a cascade of deactivation” through a pathway including the hippocampus, thalamus, and medial prefrontal cortex, followed by a broader rise in brain activity across the cortex during prolonged unconsciousness. “Furthermore, sliding window analysis demonstrates a temporary increase in fMRI signal synchronization in the hippocampus-thalamus-medial prefrontal cortex pathway before loss of consciousness,” can we read in the works.
An increase in activity in other cortical regions, a consequence of loss of consciousness
“Although these brain regions have been implicated in unconscious states in the existing scientific literature, our research is the first to indicate how these regions may interact with each other and what type of role they may play at the time of loss of consciousness. awareness”, said Nanyin Zhang, who participated in the study. These data suggest that loss of consciousness may be triggered by sequential events in these three regions, while increases in activity in other cortical regions may be a consequence, rather than a cause, of loss of consciousness.
