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use of magnetic resonance imaging (MRI) to show the position in the brain of increases in blood volume and blood oxygenation during brain activation. Positron emission tomography (PET) can also show quantitative changes in metabolism during verbal processing, as indicated by spots of increased activity superposed on the MRI anatomic image of the cortex in the same subject. (Illustration courtesy of U. Pietrzyk and D. Heiss, Max Planck Institut, Koln, Germany.)

Plate 1.7. The concentrations of neurotransmitters and neuroreceptors in the brain are 1 million times lower than the concentration of amino acids, sugars, enzymes, and other constituents of the brain. However, these trace neurochemicals can be detected by positron emission tomography (PET). Depicted here are (left to right) the concentrations of dopamine receptors at three anatomic levels of the brain for two subjects, one with a normal number of receptors and one with a decreased number of receptors resulting from a cocaine addiction. (Illustration courtesy of N. Volkow and J. Fowler, Brookhaven National Laboratory.)

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Plate 1.1

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Plate 1.2

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Plate 1.3

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Plate 1.4

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Plate 1.5

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Plate 1.6

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Plate 1.7



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