BBC says US scientists have partially revived pig brains four hours after the animals were slaughtered.
The findings could
fuel debate about the barrier between life and death, and provide a new way of
researching diseases like Alzheimer's.
The study showed the
death of brain cells could be halted and that some connections in the brain
were restored.
However, there were no
signals from the brain that would indicate awareness or consciousness.
The surprise findings
challenge the idea that the brain goes into irreversible decline within minutes
of the blood supply being cut off.
How it was done.
Thirty-two pig brains
were collected from an abattoir.
Four hours later the
organs were connected to a system made by the team at Yale University.
It rhythmically pumped
(to mimic the pulse) a specially designed liquid round the brain, which
contained a synthetic blood to carry oxygen and drugs to slow or reverse the
death of brain cells.
The pig brains were
given the restorative cocktail for six hours.
The study, published in
the journal Nature, showed a reduction
in brain cell death, the restoration of blood vessels and some brain activity.
The researchers found
working synapses, the connections between brain cells that allow them to
communicate.
The brains also showed
a normal response to medication and used up the same amount of oxygen as a
normal brain.
This was all 10 hours
after the pigs were decapitated.
Crucially there was no
sign of the brain, wide electrical activity in an electroencephalogram (EEG
brain scan) that would signal awareness or perception.
Fundamentally they
were still dead brains.
The research
transforms ideas about how the brain dies, which many thought happened quickly
and irreversibly without a supply of oxygen.
Prof Nenad Sestan, a
professor of neuroscience at Yale University, said: "Cell death in the
brain occurs across a longer time window that we previously thought.
"What we are
showing is the process of cell death is a gradual, stepwise process.
"And that some of
those processes can be either postponed, preserved or even reversed."
The pig brains came
from the pork industry; the animals were not raised in a lab for this
experiment.
But the Yale
scientists were so concerned the pigs might become conscious that they gave
drugs to the disembodied brains to reduce any brain activity.
And the team were
constantly monitoring the brains to see if there was any sign of higher brain
functions.
In that case they
would have used anaesthetic and ended the experiment.
Ethicists, writing in
Nature, say new guidelines are needed for this field because animals used for
research could end up in a "grey area,not alive, but not completely
dead".
The immediate benefit
of this work will be for scientists studying the brain in diseases like
Alzheimer's.
The organ is the most
complex structure in the known universe, but techniques such as freezing slices
of the brain or growing colonies of brain cells in a dish do not let
researchers explore the full 3D wiring of the brain.
In the long term,
scientists hope to find better ways of protecting the brain after traumas such
as a stroke or being starved of oxygen at birth.
Dr Andrea
Beckel-Mitchener, from the Brain Initiative at the US National Institute of
Mental Health, said: "This line of research could lead to a whole new way
of studying the post-mortem brain.
"It also could
stimulate research to develop interventions that promote brain recovery after
loss of brain blood flow."
However, the
researchers say it is still far too early for the field to make a difference to
patients after injury.
Prof Sestan said:
"We don't yet have knowledge whether we would be able to restore normal
brain function."
At the moment no, but
some ethicists say we should have the debate now as people who are "brain
dead" are a major source of organs for transplant.
Prof Dominic
Wilkinson, a professor of medical ethics and a consultant neonatologist in
Oxford, said: "Once someone has been diagnosed as 'brain dead' there is
currently no way for that person to ever recover.
"The human person
that they were has gone forever.
"If, in the
future, it were possible to restore the function of the brain after death, to
bring back someone's mind and personality, that would, of course, have
important implications for our definitions of death."
But that is not
currently the case.
Prof Tara
Spires-Jones, deputy director of the Centre for Discovery Brain Sciences at the
University of Edinburgh, said: "This study is a long way from preserving
human brain function after death as portrayed in the cartoon Futurama where
heads were kept alive in a jar.
"It is instead a
temporary preservation of some of the more basic cell functions in the pig brain,
not the preservation of thought and personality."