Molecular imaging of the dopaminergic system and its association with human cognitive function

Molecular imaging with positron emission tomography (PET) and single photon emission computed tomography (SPECT) has recently been used to examine dopamine (DA)Junction and its relationship with cognition in human subjects. This article will review PET and SPECT studies that have explored the relationship between cognitive processes and components of the DA system (pre-, intra-, and postsynaptic) in healthy and patient populations such as Parkinsons disease (PD), schizophrenia, Huntington's disease, and aging. it is demonstrated that DA activity modulates a range of frontal executive-type cognitive processes such as working memory, attentional functioning, and sequential organization, and alterations of DA within the fronto-striato-thalamic circuits might contribute to the cognitive impairments observed in PD, schizophrenia, and normal aging. Although associations between DA and cognitive measures need to be considered within the context of fronto-striato-thalamic circuitry, it is suggested that striatal (especially caudate) DA receptors, might be important for response inhibition, temporal organization of material, and motor activity, particularly via D-2 receptors might be important for response inhibition, temporal organization of material, and motor performance, whereas conical DA transmission via D-1 receptors might be important for maintaining and representing on-going behavior.