Image: Nicol & Morton / Scientific Reports
Scientists at Cambridge University have found a previously unknown phenomenon that is associated with the activity of the brain. With the introduction of large doses of the anesthetic ketamine in the body of the sheep, the researchers observed almost complete shutdown of normal brain activity in the cerebral cortex that lasted several minutes. This was reported in an article published in the journal Scientific Reports.
Animals were given different doses of ketamine ranging from very low (3 milligrams per kilogram of body weight) to high (24 milligrams per kilogram). Regardless of the dose, in sheep was observed three phases of brain activity: a period of calm, then dissociation of consciousness without volitional movements, and, finally, a period of almost full alertness, but also without movement. During the transition from the first phase to the second, the researchers observed an intermediate state of the brain, which switches between low and high frequency rhythms.
As the authors write, although the subjective experience of animals in each phase can be defined similar clinical and psychological peculiarities observed in people who injected ketamine. But at the highest doses, the electroencephalograph (EEG) ceased to record brain activity in five out of six sheep. This phenomenon has been called EEG-hole (eng. EEG hole). The period came two minutes after administration of ketamine.
According to the researchers, EEG-hole does not lead to complete cessation of brain activity, otherwise the animals would stop to breathe. After a few minutes the brain activity returns to the level characteristic of the low-dose ketamine. The mechanism by which this substance causes these effects remains unknown.
Video, photo All from Russia.