"Some say the tunnel is a symbolic representation of the gateway to another
world. But then why always a tunnel and not, say, a gate, doorway, or even
the great River Styx? Why the light at the end of the tunnel? And why
always above the body, not below it?"
-- Susan Blackmore, 1991, Skeptical Enquirer
One of the most unusual applications of computer software in the 1990's
has been to study the visual experiences reported by people who have almost
died. Many people, who have "come back" from states close to death, have
reported pleasant experiences at death's door. Some have reported seeing
lights at the end of a dark tunnel. Susan Blackmore, a researcher with the
Department of Psychology at the University of Bristol, along with colleague
Tom Troschianko, used a computer program to answer the question: Why do
almost-dead people see tunnels?
Researchers in the past have shown that several patterns are likely to
appear to people whose brains have been subject to drugs or abnormal
electrical stimulation as occurs in epilepsy. These patterns include the
tunnel, and the cobweb. Their origin has been thought to lie in the
structure of the visual cortex, the part of the brain concerned with vision.
Blackmore and Troschianko's computer program simulates what would happen
when there is gradually increasing electrical noise in the visual cortex.
The computer program starts with thinly spread dots of light, with more
towards the middle, and very few at the edges of the pattern. (Blackmore
notes that in the cortex there are many more cells representing the center
of the visual field but very few for the edges.) When the computer
simulation is run, gradually the number of dots increases, and the center
begins to look like a white blob. The researchers where shocked to see on
their displays a dark speckled tunnel with a white light at the end. The
light grows bigger and bigger (giving the appearance that the observer is
getting nearer and nearer) until it fills the whole screen. Is this the
tunnel some see at the threshold of death? It may be too early to answer
this with any certainty. Blackmore notes, "Our program and theory also
make a prediction about near-death experiences in the blind. If they are
blind because of problems in the eye but have normal cortex, then they too
should see tunnels."
If you wish to aze at the eerie and crepusclar death-tunnels produced by
their computer simulations, see Blackmore's 1991 Skeptical Inquirer article.
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