Scientists record gamma waves in the brain of people who was about to die

(Wikimedia Commons/David S. Soriano https://bit.ly/42kjrav)

Two dying patients showed a marked increase in brain gamma activity in the area of the cortex, which is responsible for conscious visual perception.

In addition, there was an increase in the activity of interlobar bonds in the gamma range.

Near-death experiences are often described in the same way by survivors from a wide variety of cultures: out-of-body experiences with euphoria or a loss of sense of space and time.

Researchers have found the registration of high-frequency oscillations on the EEG in such people, which some scientists consider as a marker of consciousness.

Animals, in particular, found an increase in gamma activity on the EEG after cardiac arrest.

It is believed that the gamma rhythm reflects the conscious perception of visual information and increased concentration.

Conscious perception of visual stimuli is associated with two pathways: one passes through the occipital-temporal gyrus, and the other through the occipito-parietal junction.

These temporo-parieto-occipital connections (including both gray and white matter) mediating visual information processing are considered, among other things, to be the zone of neural correlates of consciousness.

THE OBSERVATIONS
Now, scientists led by Jimo Borjigin from the University of Michigan retrospectively examined the EEG of four dying people in a coma who were on a ventilator.

Three of them died due to hypoxic brain damage after cardiac arrest, and one due to massive cerebral hemorrhage.

Within the last 24 hours, two patients have seen seizure activity on the EEG.

In the first patient, doctors detected flashes of a gamma rhythm (frequency from 30 to 120 hertz, amplitude 2-10 microvolts) in the left anteriomedian part of the temporal lobe (T3) before death.

The amplitude of those flashes increased within a few seconds after the cessation of mechanical ventilation throughout brain, and especially in the frontal and central regions.

The same was observed on the EEG in another patient.

In the late stages of dying in the right and left temporal lobes, the gamma rhythm continued to appear in the form of flashes.

Also active in the gamma rhythm were the somatosensory cortex (C3 and C4), the dorsolateral prefrontal cortex on the right (F4), and the ventrolateral prefrontal cortex on both sides (F7, F8).

In general, throughout the entire brain, doctors observed all brain rhythms for a short time, but gamma rhythms were recorded more often and with greater amplitude.

The amplitude of gamma-rhythms in the right anteriomedian part of the temporal lobe (T4) was significantly associated with the phase of the lower frequency ranges.

Also, the strength of this relationship changed dynamically at different stages of dying: for example, it was absent shortly before the ventilator was turned off.

However, this relationship was especially increased markedly in the somatosensory and dorsolateral prefrontal cortex.

In addition, the EEG recorded the propagation of gamma rhythms between the right parietal lobe and the right posterior temporal lobe, which then passed into the occipital lobe.

Thus, scientists recorded gamma-rhythms in the areas of the brain that are responsible for the perception of visual information in two dying patients who were turned off the ventilator.

According to the team, the activation of gamma rhythms can be considered a compensatory reaction in acute cerebral hypoxia.

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