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7 Cards in this Set
- Front
- Back
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computerized axial tomography (CT or CAT scan)--
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method for studying the brain; a physician injects a dye into the blood ( to increase contrast in the image) and them places the person's head into a Ct scanner. X-rays are passed through the head and recoded by detectors on the opposite side. The CT scanner is rotated slowly until a measurement has been take ate each angle over 180 degrees. From the measurements, a computer constructs images of the brain.
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magnetic resonance imaging (MRI)--
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method based on the fact that any atom with an odd-number atomuc weight, such as hydrigen, has an axis of rotation. An MRI device applies a powerful magnestic field (about 25000 times the magnetic field of the earth) to align all the axes of rotation and them tilts them with a brief radio frequency field. When the radio frequency field is truned off, the atomic nuclei release electromagnetic energy as they relax and return to their original axis. By measuring that energy, MRI devices form an image of the brain.
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electroencephalograph (EEG)--
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a device that record electrical activity of the brain through electrodes -- ranging from just a few to more than a hundred -- attached to the scalp.
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evoked potential--
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activity in respond to stimulus
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magnetoencephalograph (MEG)--
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measures the faint magnetic fielfs generated by brain activity. Like EEG, an MEG recording identifies only the approximate location of activity to within about a centimeter. However, MEG has excellent temporal resolution, showing changes from 1ms to another.
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positron emission tomography (PET)--
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provides a high-resolution image of activity in a living brain by recording the emission of radioactivity from injected chemicals. First, the person receives and injection of glucose or some other chemical containing radioactive atoms. The person's head is placed in a machine similar to a CT scanner. The computer determines which regions of the brain have taken up the radioactive substance, and it produces a picture of the slice of the brain (and activation levels of certain regions).
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Functional magnetic resonance imaging (fMRI)--
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a modified version of the MRI based on hemoglobin (the blood protein that bins oxygen). Hemoglobin with oxygen reacts to a magnetic field differently from hemoglobin without oxygen. Because oxygen consumption increases in the brain areas with the greatest activity, researchers can set the fMRI scanner to detect changes in the oxygen content of the blood and thereby measure the relative levels of brain activity in the various areas. An fMRI image has a spatial resolution of 1 or 2 mm (almost as good as a standard MRI) and temporal resolution of about a second.
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