[Examination of psychological functions by functional imaging with positron emission tomography and magnetic resonance imaging].

Changes in regional cerebral blood flow (rCBF) during experimentally modified psychological activation can be measured using radioactive ligands with positron emission tomography (PET) and using magnetic resonance principles with functional magnetic resonance imaging (fMRI). With PET it is possible to determine not only rCBF, but also metabolic changes, as well as the density and binding of several neuroreceptors. This can be done in conjunction with psychological and pharmacological challenge. fMRI is an imaging technique for perfusion-based signal intensities of the brain which does not involve radioactivity and gives better anatomical and temporal resolution than PET. Under appropriate experimental conditions, subjects' behavior and experience can be modified while they are lying in a tomograph. These experiments can be used for the scientific investigation of cognitive constructs such as memory and attention, or emotional processes. In this review, both functional neuroimaging techniques are assessed.