Second order components of moving plaids activate extrastriate visual cortex: A positron emission tomography study

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Correlation of memory dysfunction and amyloid burden in mild cognitive impairment

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Nicotinic receptors are not responsible for improved cognitive performance by galantamine in early Alzheimer's disease: A 2-[18F]F-A-85380 PET study

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Differentiation between Alzheimer's disease patients and healthy controls is not possible with 2-[18F]F-A-85380 PET imaging of nicotinic receptors

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The Relationship Between Nicotinic Receptors and Cognitive Functioning in Healthy Aging: An In Vivo Positron Emission Tomography (PET) Study With 2-[F-18]Fluoro-A-85380

Extensive experimental and neuropathological evidence supports the general hypothesis that decline in the basal forebrain cholinergic system contributes significantly to age-related cognitive impairment. Postmortem studies suggest reductions in neuronal nicotinic acetylcholine receptors (nAChRs, particularly the α4β2 subtype) with aging. This study aimed to determine the distribution of α4β2-subtype nAChRs in vivo by 2-FA PET in healthy subjects (aged 21-83) and to establish whether there is an age-related decline in nAChRs. Furthermore, the relationship between PET measures of 2-FA binding and neurobehavioral measures of cognitive function was investigated. All participants were nonsmokers and underwent extensive cognitive testing and a PET scan after injection of 2-FA (200 MBq). Brain regional 2-FA binding was assessed through a simplified estimation of distribution volume (DVS). As expected, increasing age was associated with poorer cognitive performance, particularly on tasks assessing episodic memory and attentional processes. No significant age-related differences in regional nAChR DVS were found. Furthermore, no significant correlations were found between cognitive measures and nAChR DVS. These results are consistent with recent studies suggesting the stability of cholinergic markers during senescence. It is plausible that changes in α4β2 nAChRs do occur with advancing age, but are beyond detection by the clinical 2-FA PET approach adopted here. However, this approach may be appropriate for use in pathologies considered to undergo extensive nAChR loss such as Alzheimer's disease and Parkinson's disease.12 page(s

Amyloid burden in ageing subjects with and without cognitive decline

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Statistical parametric mapping of hypoxic tissue identified by [F-18]fluoromisonidazole and positron emission tomography following acute ischemic stroke

Positron emission tomography (PET) and the ligand [F-18]fluoromisonidazole (F-18-FMISO) have been used to image hypoxic tissue in the brain following acute stroke. Existing region of interest (ROI)-based methods of analysis are time consuming and operator-dependent. We describe and validate a method of statistical parametric mapping to identify regions of increased F-18-FMISO uptake. The 18F-FMISO PET images were transformed into a standardized coordinate space and intensity normalized. Then t statistic maps were created using a pooled estimate of variance. Statistical inference was based on the theory of Gaussian Random Fields. We examined the homogeneity of variance in normal subjects and the influence of normalization by mean whole brain activity versus mean activity in the contralateral hemisphere. Validity of the distributional assumptions inherent in parametric analysis was tested by comparison with a non-parametric method. The results of parametric analysis were also compared with those obtained with the existing ROI-based method. Variance in uptake at each voxel in normal subjects was homogeneous and not affected by mean voxel activity or distance from the centre of the image. The method of normalization influenced results significantly. Normalization by whole brain mean activity resulted in a smaller volume of tissue being classified as hypoxic compared to normalisation by mean activity in the contralateral hemisphere. The ROI-based method was subject to interobserver variability with a coefficient of variability of 16%. The volumes of hypoxic tissue identified by parametric and nonparametric methods were highly correlated (r = 0.99). These findings suggest that using a pooled variance and contralateral hemisphere normalisation, statistical parametric mapping can be used to objectively identify regions of increased F-18-FMISO uptake following acute stroke in individual subjects. (C) 2002 Elsevier Science (USA)