Original research · Frontiers in Aging Neuroscience · 2022

The last signal did not arrive as silence.

A rare 900-second EEG recording around cardiac arrest changed its mix before it faded. Slower rhythms weakened. For a short window, gamma occupied a larger share of what the electrodes still recorded.

One patient. One clinical case. Electrical activity is not a report of consciousness.

Read the trace

EEG / peri-arrest window900 s

Sseizure

LSleft suppression

BSbilateral suppression

CAcardiac arrest

The recording moves through four windows. The signal changes shape before it reaches the post-arrest segment.

01patient

04analysis windows

30 seach comparison

16EEG channels

Read the result first

As the recording moved toward arrest, the mix changed before it faded.

Gamma took up more of the signal

Broad-band gamma rose from 0.93% of relative power in the interictal window to 8.43% during bilateral suppression. Its absolute power also peaked in that window.

Slow rhythms lost coherence after arrest

Delta, theta, and alpha coherence fell in the post-arrest window. Faster bands stayed broadly similar, with a small narrow-gamma increase.

The result is a signal relationship, not a memory trace

The paper measured voltage patterns between electrodes. It did not measure a person's experience, memory, or awareness.

All values on this page come from Vicente et al., 2022. Read the original paper ↗

Four windows, one recording

The trace makes more sense when you stop treating it as one thing.

Each window is a 30-second slice chosen by the authors. Select one to compare the relative share of the six frequency bands. Relative power answers a narrow question: what portion of the analysed signal sits in each band?

II / interictal interval

The reference window

385–415 seconds

This is the comparison point after seizure activity and before the recorded suppression stages. Delta dominates the analysed power, while gamma remains a small share.

slow bandsgamma bandsrelative power · %

49.86%

delta0.5–5 Hz

1.43%

theta5–10 Hz

0.58%

alpha10–15 Hz

0.78%

beta15–25 Hz

1.36%

γ narrow30–60 Hz

0.93%

γ broad80–150 Hz

In this window, the broad-band gamma share is 0.93%. The same measure reaches 8.43% in BS.

Show the source values, including absolute power

Table 1 values transcribed from the paper
Window	Delta	Theta	Alpha	Beta	γ narrow	γ broad
II · relative %	49.86	1.43	0.58	0.78	1.36	0.93
LS · relative %	41.96	1.35	0.65	1.22	2.55	1.95
BS · relative %	27.65	0.44	0.46	1.65	5.55	8.43
Post-CA · relative %	37.32	0.98	0.61	1.14	2.33	2.34
II · absolute μV²	3.0659	0.0615	0.0200	0.0326	0.0583	0.0382
LS · absolute μV²	1.7987	0.0339	0.0134	0.0228	0.0506	0.0402
BS · absolute μV²	1.9736	0.0142	0.0140	0.0414	0.1399	0.2041
Post-CA · absolute μV²	0.8381	0.0121	0.0053	0.0093	0.0189	0.0198

Relative power is each band divided by the total power across the analysed bands. It should not be read as total brain activity.

The vocabulary of the trace

Six bands. Six different slices of time.

EEG is not one note. The analysis separates the recording by frequency, then asks how the parts change together.

Delta · 0.5–5 Hz

The slowest band in this analysis. Its absolute power declines across the recording.

Theta · 5–10 Hz

Low-frequency activity that falls sharply after left and bilateral suppression.

Alpha · 10–15 Hz

A slower rhythm that matters here because its phase modulates gamma amplitude.

Beta · 15–25 Hz

A faster band whose absolute power falls in the post-arrest window.

Narrow gamma · 30–60 Hz

One of two high-frequency bands. Its relative share rises in BS.

Broad gamma · 80–150 Hz

The band with the largest relative-power jump in the source table.

When rhythms meet

The paper found a relationship between slow phase and fast amplitude.

Phase-amplitude coupling asks whether the amplitude of a faster rhythm changes at particular points in the cycle of a slower one. Choose a window. The grid shows modulation indices from the left lateral electrode group, with the strongest published result called out in the margin.

amplitude band ↑phase band →

delta

theta

alpha

gamma broad

1.3

1.2

4.1

gamma narrow

0.7

3.3

beta

1.0

0.4

1.3

alpha

1.4

1.5

—

MI = modulation index. Higher values mean a stronger phase-amplitude relationship in this analysis.

How the signal was read

The result comes from a chain of measurements, not a single spike.

The team recorded the electrical potential at 16 scalp electrodes, alongside an EKG trace, at 512 samples per second. They then split the recording into overlapping two-second epochs, calculated power with a fast Fourier transform, and measured coupling with the Hilbert transform.

For coherence, they compared electrode pairs with a magnitude-squared coherence measure. The final charts average those pairwise relationships across the four windows.

Every step describes the recording. None of the steps can recover a private experience that was not recorded.

InputEEG + EKG8 left and 8 right leads

Sampling512 Hzstandard 10–20 system

Power2 s / 1 sepoch / overlap

Windows4 × 30 scentred on event stages

CouplingMIphase to amplitude

Coherencepairwisemagnitude-squared

Read the boundary

What this cannot tell us

A voltage trace is not a window into a mind.

The recording is striking because it captures a rare transition in a real clinical setting. It is also narrow. The patient was an 87-year-old man with traumatic subdural hematoma, seizures, medication, and severe brain injury. The study had no healthy comparison and no uninterrupted pre-event baseline.

The safest conclusion is the smallest one: in this recording, several rhythms changed together around cardiac arrest. The study does not show that the patient was conscious, replaying memories, or having a near-death experience.

The authors say the original contributions are included in the article and supplementary material. Open the supplementary material ↗

Source trail

Follow the numbers back to the paper.

01Vicente et al. (2022)Enhanced Interplay of Neuronal Coherence and Coupling in the Dying Human Brain · Frontiers in Aging Neuroscience 14:813531 02Full articleAbstract, case report, methods, results, discussion, ethics, and Table 1 / Table 2 03CC BY 4.0The article is open access. Reuse requires author and publication credit, subject to individual asset credit lines.

Adapted as an independent editorial explainer by Marius Comper. This page is educational and is not medical advice. Read the page as Markdown.