Learning face-name associations and the effect of age and performance: a PET activation study.

Learning face-name associations is a complex task to be mastered in every day life that approaches the limits of cognitive capacity in most normal humans. We studied brain activation during face-name learning using positron emission tomography (PET) in 11 normal volunteers. The most intense activation was seen in occipital association cortex (BA 18) bilaterally, also involving lingual and fusiform gyrus (BA 37). In the left hemisphere additional activation were located in inferior temporal gyrus, the inferior part of pre- and postcentral gyrus, and orbitofrontal cortex (BA 11), whereas in the right hemisphere only a region in the precuneus (BA 19) was activated additionally. There was considerable interindividual variation of encoding success, which was significantly related to activation of BA 18 bilaterally. Subject ages covered a range of 26-72 years, but - in contrast to the effect of encoding success - there was no significant age effect on activations. Task-independent habituation effects were seen in cerebellum and left middle temporal gyrus. These results indicate that the intensity of information processing in ventral occipital association cortex is most important for success of face-name encoding. Learning is further mediated by a predominantly left-hemispheric network including inferior temporal and orbitofrontal cortex.

In-vivo measurements of regional acetylcholine esterase activity in degenerative dementia: comparison with blood flow and glucose metabolism.

UNLABELLED: Memory and attention are cognitive functions that depend heavily on the cholinergic system. Local activity of acetylcholine esterase (AChE) is an indicator of its integrity. Using a recently developed tracer for positron emission tomography (PET), C-11-labeled N-methyl-4-piperidyl-acetate (C11-MP4A), we measured regional AChE activity in 4 non-demented subjects, 4 patients with dementia of Alzheimer type (DAT) and 1 patient with senile dementia of Lewy body type (SDLT), and compared the findings with measurements of blood flow (CBF) and glucose metabolism (CMRGlc). Initial tracer extraction was closely related to CBF. AChE activity was reduced significantly in all brain regions in demented subjects, whereas reduction of CMRGlc and CBF was more limited to temporo-parietal association areas. AChE activity in SDLT was in the lower range of values in DAT. Our results indicate that, compared to non-demented controls, there is a global reduction of cortical AChE activity in dementia. KEYWORDS: Dementia, cholinergic system, acetylcholine esterase, positron emission tomography, cerebral blood flow, cerebral glucose metabolism.

Positron emission tomographic analysis of the nigrostriatal dopaminergic system in familial parkinsonism associated with mutations in the parkin gene.

A kindred from South Tyrol (northern Italy) with familial, adult-onset parkinsonism of pseudo-dominant inheritance and mutations in the parkin gene was recently described. To gain insight into basal ganglia dysfunction in this form of hereditary parkinsonism, positron emission tomography (PET) with 18-fluorodopa (FDOPA) and 11C-raclopride (RAC) was performed in 5 affected family members and 5 asymptomatic relatives with proven compound heterozygous or heterozygous parkin mutations. Results were compared to findings in healthy control subjects and patients with typical sporadic, idiopathic Parkinson's disease. Similar to findings in the sporadic Parkinson's disease group, presynaptic striatal FDOPA storage was decreased in patients with compound heterozygous parkin mutations, with the most prominent reduction in the posterior part of the putamen. Along with the presynaptic lowered FDOPA uptake, we found a uniform reduction of the striatal 11C-raclopride binding index in all affected family members as compared to asymptomatic family members carrying a heterozygous parkin mutation, sporadic Parkinson's disease, and control subjects. Our PET data provide evidence that parkinsonism in this family is associated with presynaptic dopaminergic dysfunction similar to idiopathic Parkinson's disease pathophysiology, along with alterations at the postsynaptic D2 receptor level. In asymptomatic carriers of a single parkin mutation with an apparently normal allele, we found a mild but statistically significant decrease of mean FDOPA uptake compared to control subjects in all striatal regions. These data indicate a preclinical disease process in these subjects.