[Neuroimaging and cocaine: mapping dependence?].

Two principal techniques are used in functional neuroimaging: positron-emission tomography (PET) and functional magnetic resonance imaging (fMRI). FMRI is noninvasive and non-irradiating; it has good temporal and spatial resolution, but it is not at all specific. PET has a lower spatial and temporal resolution but better sensitivity and high specificity. Functional neuroimaging studies in individuals who are and are not cocaine-dependent have confirmed the blockage of cerebral dopamine transporters by acute cocaine intake and the mechanism of down-regulation in chronic consumers. This blockage is expressed by depletion of dopaminergic D2 postsynaptic receptors and low levels of dopamine release. Variations in the protocols and in the results of neuroimaging studies of craving make their interpretation difficult, although several cerebral structures do appear to be particularly involved. Neuroimaging has no recognized clinical indications in the field of dependence or more generally in psychiatry, but it is an essential research tool.