ИСТИНА

It is beyond argument that the consciousness is a product of the brain with a key role of the cortex, nevertheless, the role of midbrain in consciousness is still discussed. The point of view that the brainstem is crucial to the consciousness was developed by Merker [2]. He supposed that a basic level of consciousness is possible to observe in children with anencephaly. The present study aimed to carry out frequency analysis between cortex and midbrain area (periaqueductal grey) in the process of consciousness recovery. The study included the patient with tumor of the pineal region who underwent tumor removal by anterior interhemispheric approach. After removal of the tumor at the final stage of the operation a specially developed external ventricular drainage was installed for 24 hours for the purpose of draining cerebrospinal fluid and preventing possible cerebrospinal fluid circulation disorders. The multi-perforated distal end of the drainage was inserted into the lumen of the aqueduct to the upper sections of the fourth ventricle. The electrodes were mounted at this end of the drainage which were wired inside the drainage tube and connected to the recording device. The diameter of the drainage (2.5 mm) in the aqueduct ensured close contact of the electrodes with the internal surface of the aqueduct in close proximity to periaqueductal grey. More information about the operation technique is available in the study [3,4]. The electrode placement was determined on the basis of computer tomography imaging. Scalp brain potentials were recorded from electrodes located by the 10-20. Brain activity recording started in the intensive care department and lasted for 24 hours after operation. It included the following states of consciousness: deep propofol anesthesia (near to isoline in the cortex), propofol anesthesia, dexdor anesthesia, obnubilation and clear consciousness. Brain signals were analyzed with matlab Brainstorm toolbox. There were periods of attenuation of cortical activity and bursts of alpha rhythm in deep propofol anesthesia. In the first case the cortical activity tends to line but the midbrain activity was in general more than two times higher than cortical activity. During bursts of alpha rhythm the amplitude of signal from occipital and parietal sensors were higher than midbrain amplitude in the range from 5 to 25 hertz. The peak at 12 hertz was particularly prominent in both types of sensors: scalp and deep electrodes. In the process of consciousness restoration the amplitude signals from the scalp and midbrain increased but the rate of this growth was different. As a result, the amplitude of cortex signal had become much higher than amplitude of brainstem signal in the entire frequency range in state of clear consciousness. Also in state of clear consciousness, the form of deep activity was close to the cortical waves. The data obtained in the study are discussed in connection with midbrain-cortex functional connectivities in disorders of consciousness. The study was supported by RFFI 18-013-00967a.