Results 11 to 20 of about 3,448,461 (253)

Structural Covariance in the Human Cortex [PDF]

The Journal of Neuroscience, 2005
The morphology of the human cortex varies remarkably across individuals, regardless of overall brain size. It is currently unclear whether related cortical regions covary in gray matter density, as a result of mutually trophic influences or common experience-related plasticity.
Mechelli, A, Friston, K J, Frackowiak, R S, Price, C J   +3 more
openaire   +3 more sources

The genetical analysis of covariance structure [PDF]

Heredity, 1977
The analysis of covariance structures (Jöreskog, 1973) is adapted to the simultaneous maximum likelihood estimation of genetical and environmental factor loadings and specific variances. The goodness of fit is tested by chi square and standard errors of parameter estimates can be obtained.
N G, Martin, L J, Eaves
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Age-Related Regional Network Covariance of Magnetic Resonance Imaging Gray Matter in the Rat

Frontiers in Aging Neuroscience, 2020
Healthy human aging has been associated with brain atrophy in prefrontal and selective temporal regions, but reductions in other brain areas have been observed.
Gene E. Alexander, Gene E. Alexander, Gene E. Alexander, Gene E. Alexander, Gene E. Alexander, Gene E. Alexander, Lan Lin, Lan Lin, Lan Lin, Eriko S. Yoshimaru, Pradyumna K. Bharadwaj, Pradyumna K. Bharadwaj, Pradyumna K. Bharadwaj, Kaitlin L. Bergfield, Kaitlin L. Bergfield, Kaitlin L. Bergfield, Lan T. Hoang, Lan T. Hoang, Lan T. Hoang, Monica K. Chawla, Monica K. Chawla, Monica K. Chawla, Kewei Chen, Kewei Chen, James R. Moeller, Carol A. Barnes, Carol A. Barnes, Carol A. Barnes, Carol A. Barnes, Carol A. Barnes, Carol A. Barnes, Carol A. Barnes, Carol A. Barnes, Theodore P. Trouard, Theodore P. Trouard, Theodore P. Trouard   +35 more
doaj   +1 more source

Testing for instability in covariance structures [PDF]

Bernoulli, 2018
We propose a test for the stability over time of the covariance matrix of multivariate time series. The analysis is extended to the eigensystem to ascertain changes due to instability in the eigenvalues and/or eigenvectors. Using strong Invariance Principles and Law of Large Numbers, we normalise the CUSUM-type statistics to calculate their supremum ...
Kao C, Trapani L, Urga G
openaire   +7 more sources

IDENTIFICATION OF COVARIANCE STRUCTURES [PDF]

Econometric Theory, 2006
Summary: The issue of identification of covariance structures, which arises in a number of different contexts, has been so far linked to conditions on the true parameters to be estimated. In this paper, this limitation is removed. As done by \textit{S. Johansen} [J. Econom. 69, No.
openaire   +1 more source

Shared alterations in hippocampal structural covariance in subjective cognitive decline and migraine

Frontiers in Aging Neuroscience, 2023
IntroductionSubjective cognitive decline (SCD) and migraine are often comorbid. Hippocampal structural abnormalities have been observed in individuals with both SCD and migraine. Given the known structural and functional heterogeneity along the long axis
Chia-Lin Tsai, Kun-Hsien Chou, Kun-Hsien Chou, Pei-Lin Lee, Chih-Sung Liang, Chen-Yuan Kuo, Guan-Yu Lin, Yu-Kai Lin, Yu-Kai Lin, Yi-Chih Hsu, Chien-An Ko, Fu-Chi Yang, Fu-Chi Yang, Ching-Po Lin, Ching-Po Lin, Ching-Po Lin   +15 more
doaj   +1 more source

Covariant spin structure [PDF]

Journal of Mathematical Physics, 1998
Dirac fermion fields associated with different tetrad gravitational fields and under general covariant transformations are described by sections of the composite bundle S→Σ→X4, which is both the Dirac spinor bundle over the tetrad bundle Σ and the natural one over X4. As a natural bundle, S→X4 admits general covariant transformations which are those of
openaire   +2 more sources

Estimation of a Multiplicative Covariance Structure [PDF]

SSRN Electronic Journal, 2016
We consider a Kronecker product structure for large covariance matrices, which has the feature that the number of free parameters increases logarithmically with the dimensions of the matrix. We propose an estimation method of the free parameters based on the log linear property of this structure, and also a Quasi-Likelihood method.
Hafner, Christian M., Linton, Oliver Bruce, Tang, Haihan   +2 more
openaire   +2 more sources

Age-related changes in processing speed: unique contributions of cerebellar and prefrontal cortex

Frontiers in Human Neuroscience, 2010
Age-related declines in processing speed are hypothesized to underlie the widespread changes in cognition experienced by older adults. We used a structural covariance approach to identify putative neural networks that underlie age-related structural ...
Mark A Eckert, Noam I Keren, Donna R Roberts, Vince D Calhoun, Kelly C Harris   +4 more
doaj   +1 more source

Linear transformations of variance/covariance matrices [PDF]

, 2011
Many applications in crystallography require the use of linear transformations on parameters and their standard uncertainties. While the transformation of the parameters is textbook knowledge, the transformation of the standard uncertainties is more ...
Sub Crystal and Structural Chemistry, Crystal and Structural Chemistry, Lutz, M., Rontgen participation programme, Pascal Parois, Parois, P.J.A., Martin Lutz   +6 more
core   +1 more source