Near-death experiences can occur in conditions of clinical death, severe trauma, or moments when a person's life is in danger. In such moments, out-of-body sensations, visions of light or a tunnel, encounters with deceased loved ones, and a profound sense of peace are often reported. Despite many years of research, a unified theory explaining this phenomenon has yet to be achieved. Against this backdrop, the NEPTUNE theory has emerged, representing an attempt to consolidate all existing neurobiological explanations.
The developers of the theory suggest that near-death experiences are triggered by a chain reaction of physiological processes: changes in the gas composition of the blood, activation of specific areas of the brain, such as the temporoparietal junction, and the release of psychedelic substances. An important element of the model is the concept of the "death spike" — a sudden increase in brain activity in dying patients, which may be linked to vivid experiences.
The key idea of NEPTUNE is the assumption that out-of-body experiences arise from the activation of the temporoparietal junction. This can indeed create a feeling of "disembodiment" or the presence of a "shadow figure." However, such sensations are not identical to full-fledged out-of-body experiences that people describe in near-death states. During brain stimulation experiments, patients realize they are experiencing only an illusion, whereas those who have undergone a near-death experience describe their sensations as whole and emotionally rich.
Moreover, the NEPTUNE argument regarding the "death spike" in brain activity also raises questions. The model claims that this spike is the cause of vivid experiences. However, critics point out that in the studies it references, patients experiencing spikes had a beating heart, which excludes the state of clinical death. Additionally, research from 2023 showed that there are no correlations between spikes in brain activity and near-death experiences: those who reported such experiences had no signs on EEG and vice versa.
The authors also criticize the use of the term "hallucinations." Neurological hallucinations are typically frightening and disorienting, affecting one sense. In contrast, near-death experiences are multisensory and structured; they are perceived as meaningful and comforting. Memories of these experiences can last for decades and often lead to profound changes in worldview. According to researchers, these features do not fit well into an explanation based solely on the functioning of the dying brain.
Within the scientific community, there is a general consensus: while physiological factors likely play a role in the emergence of near-death experiences, they cannot fully explain them. A broader approach is needed for a deeper understanding of the nature of these states, one that takes into account the full range of data, including observations that do not fit existing notions of consciousness.
