Neurochemical and Neuropharmacological Imaging in Schizophrenia

Over the last 15 years, the ability to measure specific molecules and proteins in the living human brain underwent enormous developments, opening direct windows into neurotransmitter functions and cellular processes associated with health and disease. These techniques are based either on the injection of radioactive moieties whose distribution is recorded with positron emission tomography (PET) or single photon emission computed tomography (SPECT), or on the direct detection of molecules based on their intrinsic magnetic properties with magnetic resonance spectroscopy (MRS). Although lacking the level of resolution of postmortem studies and limited by the relatively small number of targets that can be currently studied in vivo, these imaging techniques provide unique opportunities for elucidation of pathophysiology associated with neuropsychiatric conditions. In vivo imaging techniques enable studying patients with welldocumented psychopathology, relating biochemical observations to psychiatric symptoms and cognitive processes, and clarifying abnormalities associated with the disease as opposed to its treatment. Neurochemical imaging allows longitudinal studies to investigate mechanisms of actions and consequences of treatments, as well as to characterize neurochemical abnormalities in relation to treatment response and illness outcome. Neurochemical imaging further provides insight as to the pathophysiologic bases of alterations measured with flow and metabolism imaging studies, and can provide a direct link with animal models of the illness. Moreover, these techniques enable the study of patient’s relatives, in order to clarify the endophenotypes associated with illness vulnerability. These potentialities are discussed in this chapter.