PHILIPPE PLAILLY / SCIENCE PHOTO LIBRARY PHILIPPE PLAILLY / SCIENCE PHOTO LIBRARY
Positron emission tomography (PET) scan of the brain of a person with senile dementia (Alzheimer's disease). The colour-coded scan uses a radioactive tracer to reveal variations in metabolic activity within the brain. Normal metabolic activity in the neurones (nerve cells) of a healthy brain would produce a roughly symmetrical pattern, with red areas in the left & right cerebral hemispheres. The patchy appearance of this scan indicates diffuse degeneration of brain tissue. Symptoms include memory disorders, changes in personality, confusion and disorientation. The cause is unknown and no curative treatment is yet available.
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