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- Scientists have found the strongest evidence yet that
some animals could have "souls", writes Jonathan Leake.
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- They have located the cells responsible for self-consciousness
in the human brain - and found similar clusters in great apes. The cells,
named "self-awareness neurons", appear to integrate the work
of various parts of the brain - and create a sense of individuality.
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- The suggestion that consciousness is a physical process
is certain to provoke religious controversy as well as debate over the
ethical treatment of great apes. Some would argue that if they have a sense
of self-awareness then they should also get some "human" rights.
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- The role of the neurons in humans has been confirmed
in studies of patients in which the cells had been damaged by head injuries.
Such patients lost all sense of being an individual and sank into a near-vegetative
state.
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- Professor John Allman, of the California Institute of
Technology, discovered the neurons in the frontal lobe of the brain. They
are large and lie near the corpus callosum, which connects the brain's
two halves.
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- More evidence comes from brain scans of people with mental
illnesses. The anterior cingulate cortex - the area where the cells are
found - becomes less active in depressed people and the cells may shrink.
Conversely, in people with manic disorders, the cells enlarge and become
more active.
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- Further evidence comes from studies of Alzheimer's disease.
The cells appear to be especially vulnerable and patients' loss of self-identity
correlates closely with the disappearance of the self-awareness neurons.
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- Allman examined their role in animals by seeking the
same cells in the brains of 28 primate species and 20 non-primates, including
bats and dogs. The concentration of the neurons was greatest in humans,
smaller in chimps and still less in gorillas. They could not be found in
non-primates, though it is suspected that elephants and dolphins also have
them.
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