Accumulating evidence suggests that subjective cognitive complaints (SCC) may indicate subtle cognitive decline characteristic of individuals with preclinical Alzheimer’s disease (AD). In this study, we sought to build upon previous studies by associating SCC and amyloid-β deposition using Positron Emission Tomography with Pittsburg Compound B (PiB-PET) in cognitively normal older individuals. One-hundred thirty one subjects (mean age 73.5 ± 6) were administered three subjective cognitive questionnaires and a brief neuropsychological battery. A relationship between a subjective memory complaints composite score and cortical PiB binding was found to be significant, even after controlling for depressive symptoms. By contrast, there were no significant relationships between objective cognitive measures of memory and executive functions and cortical PiB binding. Our study suggests that SCC may be an early indicator of AD pathology detectable prior to significant objective impairment.

Dietary evaluation using isotopic analyses of carbon in collagen from bone is an exciting new area of archaeological chemistry.Analyses of bone from herbivores, carnivores, and omnivores (including humans) suggest that a simple isotopic fractionation between dietary carbon and carbon in bone collagen may be an inadequate model for interpretation of results. Dietary carbohydrates are primarily metabolized for energy and their carbon is reflected mainly in the hydroxyapatite of bone. Dietary lipids are also important energy components of the diet.Dietary proteins, on the other hand, are utilized for protein (e.g. bone collagen) synthesis as needed and only excess amino acids are metabolized for energy. Herbivores, carnivores, and omnivores thus might have different isotopic fractionation models, each of which is presented.Biochemical evidence in support of these models is discussed. Isotopic studies relating to nutrition and diet have originated from two diverse fields, bio-medical research and archaeology. Numerous studies have been reported by researchers in the areas of biochemistryand medicine, using either isotopically enriched compounds or the natural variations in isotopic abundances. Such studies usually involve a specific chemical as a tracer of biochemical pathways, and in these studies soft tissues or body fluids are analyzed.Recent work in nutrition has begun to examine the isotopic composition of carbon in macronu trient s in diets and their disposition in body tissues (1.2). The isotopic composition of hard tissue (i.e., bone), however, has been largely ignored in biochemical studies.Archaeologists are often interested in dietary considerations, but normally have only bone to represent the human organism, the soft tissues having decomposed. Dietary reconstruction using

Disruption of functional connectivity between brain regions may represent an early functional consequence of β-amyloid pathology prior to clinical Alzheimer's disease. We aimed to investigate if non-demented older individuals with increased amyloid burden demonstrate disruptions of functional whole-brain connectivity in cortical hubs (brain regions typically highly connected to multiple other brain areas) and if these disruptions are associated with neuronal dysfunction as measured with fluorodeoxyglucose-positron emission tomography. In healthy subjects without cognitive symptoms and patients with mild cognitive impairment, we used positron emission tomography to assess amyloid burden and cerebral glucose metabolism, structural magnetic resonance imaging to quantify atrophy and novel resting state functional magnetic resonance imaging processing methods to calculate whole-brain connectivity. Significant disruptions of whole-brain connectivity were found in amyloid-positive patients with mild cognitive impairment in typical cortical hubs (posterior cingulate cortex/precuneus), strongly overlapping with regional hypometabolism. Subtle connectivity disruptions and hypometabolism were already present in amyloid-positive asymptomatic subjects. Voxel-based morphometry measures indicate that these findings were not solely a consequence of regional atrophy. Whole-brain connectivity values and metabolism showed a positive correlation with each other and a negative correlation with amyloid burden. These results indicate that disruption of functional connectivity and hypometabolism may represent early functional consequences of emerging molecular Alzheimer's disease pathology, evolving prior to clinical onset of dementia. The spatial overlap between hypometabolism and disruption of connectivity in cortical hubs points to a particular susceptibility of these regions to early Alzheimer's-type neurodegeneration and may reflect a link between synaptic dysfunction and functional disconnection.