Lorazepam action. Coloured positron emission tomography (PET) scans of the brain of a person on the sedative drug lorazepam. The top row shows a healthy brain from a person given only a placebo. The fronts of the brains are at top; the slices get deeper into the brain from left to right. The brighter areas (yellow, red) of the brain show areas of high activity. The brain with lorazepam shows much lower levels of activity. Lorazepam is a tranquilliser drug used to treat anxiety and insomnia. In a PET scan, radioactively-tagged molecules are injected into the bloodstream and their emissions monitored. Glucose is used here, as it is taken up by active brain cells.