Neuronal Coherence and Coupling

Neuronal Coherence and Coupling in the Dying Human Brain

It is said that when we die, our life flashes before our eyes. Those lucky enough to come back from a near-death experience have described a white light or an out-of-body experience. Unfortunately, the actual molecular and neuronal processes of a dying brain have not been studied in detail due to timing or the ethical nature of the study.

Scientists were able to capture the last moments of a dying brain in an 87-year-old man. After a fall, the patient went to the emergency room and was diagnosed with subdural hematomas. A left decompressive craniotomy was performed to alleviate cranial pressure, and he remained stable for two days before deteriorating. The patient received phenytoin, levetiracetam, and electroencephalography (EEG) that showed non-convulsive status epilepticus in the left hemisphere. After the event, twelve more seizures were recorded, leading to the development of ventricular tachycardia with apneustic respirations and clinical cardiorespiratory arrest. The patient’s family was informed, and in consideration of the “Do-Not-Resuscitate” order of the patient, no other treatment was administered, and he was allowed to die.

What they observed upon his death is an increase in gamma activity in the broad and narrow bands (gamma waves are associated with insight, concentration, and high-level information processing), as well as a significant decrease in theta wave power after the suppression of hemispheric responses. Following cardiac arrest, beta, delta, alpha, and gamma power decreased; however, a higher percentage of relative gamma power was observed during interictal intervals (the period between seizures). Using cross-frequency coupling, they revealed modulation of gamma activity in the left hemisphere influenced by alpha and theta rhythms even after blood flow had ceased to the brain. The most significant coupling was seen in narrow and broadband gamma activity powered by alpha waves during cardiac arrest.

The increase in gamma waves in both the broad and narrow band coupled with the associated brain waves indicate that a dying brain may replay, and access information processing related to memories. This study is the first of its kind to produce data in a non-experimental, real-life acute clinical setting and suggests that the human brain is capable of coordinating neuronal activity when dying. Therefore, it is possible that when we die, a movie reel of past life events is played for us one last time before we cross over to the great beyond.

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