What does death feel like?
14 Awst 2013
Mae'r cynnwys hwn ar gael yn Saesneg yn unig.
It's not a question which most of us would want to think about in great detail – the thought of what happens at the moment of death. For some the subject might be intriguing, but for others terrifying – a huge fear of the unknown.
Now researchers at the University of Michigan have published a study which offers an explanation into what is happening in the brain moments before death occurs.
Dr Jimo Borjigin and his team induced cardiac arrest in rats and analysed the electrical activity in the brain as they were dying. The information showed a surge in gamma oscillations within the first 30 seconds after cardiac arrest - a striking increase with brain activity actually exceeding the levels found during a normal conscious state.
The study raises questions about what occurs within the dying brain and whether the information can be compared to what happens to humans. People who have had near death experiences often report out of the body sensations, seeing their life flash before their eyes or the feeling of going towards a bright light or tunnel. Could this be a result of a surge in electrical activity in the brain? Could they be experiencing a higher state of consciousness?
There are perhaps more questions than answers raised by this study, and it made headlines around the globe. Cardiff University School of Psychology academics Dr Chris Chambers and Dr David McGonigle were in high demand for media comment during this time. Here are their comments from some of the media coverage:
"The paper has merely shown - and the authors are extremely clear on this point - that they have demonstrated the change in gamma oscillations occurring over a similar time period to when NDEs are experienced in humans," said Dr David McGonigle, of Cardiff University's School of Psychology. "We have no idea what the rats experience - if anything - while the increase in synchronous gamma occurs."
Doubts have also been raised over the researchers' claims that the signals observed in the dying brains of the rats were similar to a conscious state. Dr McGonigle said that scientist were still "at loggerheads" over what consciousness means, both in humans and in animals.
Dr Chris Chambers, of Cardiff University, said: "This is an interesting and well-conducted piece of research. We know precious little about brain activity during death, let alone conscious brain activity. These findings open the door to further studies in humans.
"[But] we should be extremely cautious before drawing any conclusions about human near-death experiences: it is one thing to measure brain activity in rats during cardiac arrest, and quite another to relate that to human experience."
To answer these questions we will probably need to run similar studies in humans. One approach would be to record EEG in patients during death. Would you volunteer for such a study on your deathbed? Another approach may be to induce similar bursts of gamma activity in people while they are awake and test for heightened levels of consciousness. As Cardiff University neuroscientist Dr David McGonigle puts it, "Seeing if NDEs can be triggered by neurostimulation, using experiments that induce increased gamma synchrony in humans, might represent a way to go beyond correlation to causation."
Dr David McGonigle, from University of Cardiff, said: "Do we know if animals experience 'consciousness'? Most philosophers and scientists are still at loggerheads over what the term refers to in humans, let alone in other species.
"While recent research now suggests that animals may indeed have the kind of autobiographical memories that humans possess, the kinds of memories that allow us to place ourselves in a certain time and place, it seems unlikely that near-death-experiences would necessarily be similar across species."
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