21 research outputs found
Bayesian model criticism: prior sensitivity of the posterior predictive checks method
Use of noninformative priors with the Posterior Predictive Checks (PPC) method requires more attention. Previous research of the PPC has treated noninformative priors as always noninformative in relation to the likelihood, regardless of model-data fit. However, as model-data fit deteriorates, and the steepness of the likelihood's curvature diminishes, the prior can become more informative than initially intended. The objective of this dissertation was to investigate whether specification of the prior distribution has an effect on the conclusions drawn from the PPC method. Findings indicated that the choice of discrepancy measure is an important factor in the overall success of the method, and that different discrepancy measures are affected more than others by prior specification
Novel genetic loci associated with hippocampal volume
The hippocampal formation is a brain structure integrally involved in episodic memory, spatial navigation, cognition and stress responsiveness. Structural abnormalities in hippocampal volume and shape are found in several common neuropsychiatric disorders. To identify the genetic underpinnings of hippocampal structure here we perform a genome-wide association study (GWAS) of 33,536 individuals and discover six independent loci significantly associated with hippocampal volume, four of them novel. Of the novel loci, three lie within genes (ASTN2, DPP4 and MAST4) and one is found 200 kb upstream of SHH. A hippocampal subfield analysis shows that a locus within the MSRB3 gene shows evidence of a localized effect along the dentate gyrus, subiculum, CA1 and fissure. Further, we show that genetic variants associated with decreased hippocampal volume are also associated with increased risk for Alzheimer's disease (rg =-0.155). Our findings suggest novel biological pathways through which human genetic variation influences hippocampal volume and risk for neuropsychiatric illness
Genetic architecture of subcortical brain structures in 38,851 individuals
Subcortical brain structures are integral to motion, consciousness, emotions and learning. We identified common genetic variation related to the volumes of the nucleus accumbens, amygdala, brainstem, caudate nucleus, globus pallidus, putamen and thalamus, using genome-wide association analyses in almost 40,000 individuals from CHARGE, ENIGMA and UK Biobank. We show that variability in subcortical volumes is heritable, and identify 48 significantly associated loci (40 novel at the time of analysis). Annotation of these loci by utilizing gene expression, methylation and neuropathological data identified 199 genes putatively implicated in neurodevelopment, synaptic signaling, axonal transport, apoptosis, inflammation/infection and susceptibility to neurological disorders. This set of genes is significantly enriched for Drosophila orthologs associated with neurodevelopmental phenotypes, suggesting evolutionarily conserved mechanisms. Our findings uncover novel biology and potential drug targets underlying brain development and disease
Novel genetic loci underlying human intracranial volume identified through genome-wide association
Intracranial volume reflects the maximally attained brain size during development, and remains stable with loss of tissue in late life. It is highly heritable, but the underlying genes remain largely undetermined. In a genome-wide association study of 32,438 adults, we discovered five novel loci for intracranial volume and confirmed two known signals. Four of the loci are also associated with adult human stature, but these remained associated with intracranial volume after adjusting for height. We found a high genetic correlation with child head circumference (ρgenetic=0.748), which indicated a similar genetic background and allowed for the identification of four additional loci through meta-analysis (Ncombined = 37,345). Variants for intracranial volume were also related to childhood and adult cognitive function, Parkinson’s disease, and enriched near genes involved in growth pathways including PI3K–AKT signaling. These findings identify biological underpinnings of intracranial volume and provide genetic support for theories on brain reserve and brain overgrowth
The genetic architecture of the human cerebral cortex
The cerebral cortex underlies our complex cognitive capabilities, yet little is known about the specific genetic loci that influence human cortical structure. To identify genetic variants that affect cortical structure, we conducted a genome-wide association meta-analysis of brain magnetic resonance imaging data from 51,665 individuals. We analyzed the surface area and average thickness of the whole cortex and 34 regions with known functional specializations. We identified 199 significant loci and found significant enrichment for loci influencing total surface area within regulatory elements that are active during prenatal cortical development, supporting the radial unit hypothesis. Loci that affect regional surface area cluster near genes in Wnt signaling pathways, which influence progenitor expansion and areal identity. Variation in cortical structure is genetically correlated with cognitive function, Parkinson's disease, insomnia, depression, neuroticism, and attention deficit hyperactivity disorder
FOOD INSECURITY AND EDUCATIONAL ACHIEVEMENT: A MULTI-LEVEL GENERALIZATION OF POISSON REGRESSION
This research examined the relationship between food insecurity, the National School
Lunch Program (NSLP), and academic achievement in Georgia’s public school system.
Georgia is located in the southern U.S. states, where food insecurity has been particularly
prevalent. A multilevel Poisson generalized linear model was used to examine the
relationship between food insecurity and academic achievement. Findings confirm a strong
inverse relationship between food insecurity, as exhibited by participation in the National
School Lunch Program, and academic achievement for elementary-age children. The
strength of the relationship between food insecurity and academic achievement was different
for the younger, elementary-age students (fifth grade) than for the older, middle school-age
(eighth grade) students, a key distinction between this study and other research
Food Insecurity, the National School Lunch Program and Educational Achievement: Evidence from Georgia's Public Schools
In 2011, nearly 1.7 million Georgians, 17.9% of the population, lived in poverty, and of those,
24.8% were children. Poverty is closely associated with food insecurity. Food insecurity has
been associated with various developmental consequences for U.S. children. Research indicates
that hungry children do more poorly in school and have lower academic achievement because
they are not well prepared for school and cannot concentrate. This research examines the
relationship between food insecurity, the National School Lunch Program (NSLP) and academic
achievement of 5th grade students in Georgia
Where is Our Next Meal Coming from? The Recession and Food Insecurity in the Southern U.S.
The Supplemental Nutrition Assistance Program (SNAP) is the cornerstone of
federal food assistance programs and serves as the first line of defense against food
insecurity. SNAP is especially important in the south which has the highest rate of food
insecurity in the U.S. In fiscal year 2010, SNAP accounted for 71.5% of federal spending
for primary food and nutrition assistance to low income households in the U.S. In 2010,
monthly SNAP participation averaged 40.3 million persons, up 43% in two years mainly
due to the recession of 2007-2009. This paper examines the relationship between food
insecurity, the recession, and the Supplemental Nutrition Assistance Program (SNAP) in
Georgia, 2009 and 2010. Factors associated with the rise in the number of person eligible
for SNAP benefits at the county level included the unemployment rate, education, the
percentage of African Americans in the county, and the poverty rate