MEG networks organization is related to white matter integrity

Many studies have assessed the characterization of anatomical or functional connectivity in mild cognitive impairment (MCI), however it is still unknown how they are related in the course of the pathology. Here we integrate the analysis of magnetoencephalographic (MEG) data with white matter (WM) integrity quantification from diffusion weighted imaging (DWI), to asses whether the damage in the WM tracts disrupt the organization of the functional networks.

Optimización y paralelización de algoritmo de búsqueda aleatoria para su aplicación en la búsqueda de fuentes MEG

El problema inverso de la búsqueda de fuentes MEG consiste en la obtención de la distribución de los dipolos de corriente (fuentes) en el interior de la cabeza de un paciente a partir de las mediciones de campo electromagnético obtenidas en la superficie (magnetoencefalograma, MEG). Para obtener estos datos, en el ámbito científico se utiliza el algoritmo beamforming, comúnmente aceptado, cuyos resultados ofrecen un pequeño margen de error debido a la naturaleza del problema. Esta memoria desarrolla el trabajo realizado para optimizar un algoritmo de búsqueda aleatoria, Solis-Wets, utilizado para investigar la posibilidad de su aplicación en el ámbito científico, en sustitución del anteriormente mencionado, beamforming. También se estudiará la acción de encadenar ambos algoritmos, tomando como datos de entrada del algoritmo Solis-Wets aquellos proporcionados como solución por el algoritmo beamforming con objeto de minimizar el error en el que éste incurre. Esta optimización es necesaria para que la alternativa sea viable debido al tiempo necesario en su ejecución, e incluye el uso de bibliotecas auxiliares, así como la paralelización del código. Para la evaluación del algoritmo se han medido tanto la velocidad de generación de soluciones como el error de la mejor solución tras un número determinado de soluciones generadas. Como variables para esta evaluación se han tomado distintos compiladores, distintas soluciones de partida, precisión de los datos, así como el uso de distintas bibliotecas matemáticas disponibles.

Guiding functional connectivity estimation by structural connectivity in MEG: an application to discrimination of mild cognitive impaired conditions

Whole brain resting state connectivity is a promising biomarker that might help to obtain an early diagnosis in many neurological diseases, such as dementia. Inferring resting-state connectivity is often based on correlations, which are sensitive to indirect connections, leading to an inaccurate representation of the real backbone of the network. The precision matrix is a better representation for whole brain connectivity, as it considers only direct connections. The network structure can be estimated using the graphical lasso (GL), which achieves sparsity through l1-regularization on the precision matrix. In this paper, we propose a structural connectivity adaptive version of the GL, where weaker anatomical connections are represented as stronger penalties on the corre- sponding functional connections. We applied beamformer source reconstruction to the resting state MEG record- ings of 81 subjects, where 29 were healthy controls, 22 were single-domain amnestic Mild Cognitive Impaired (MCI), and 30 were multiple-domain amnestic MCI. An atlas-based anatomical parcellation of 66 regions was ob- tained for each subject, and time series were assigned to each of the regions. The fiber densities between the re- gions, obtained with deterministic tractography from diffusion-weighted MRI, were used to define the anatomical connectivity. Precision matrices were obtained with the region specific time series in five different frequency bands. We compared our method with the traditional GL and a functional adaptive version of the GL, in terms of log-likelihood and classification accuracies between the three groups. We conclude that introduc- ing an anatomical prior improves the expressivity of the model and, in most cases, leads to a better classification between groups.

Cognitive reserve is associated with the functional organization of brain networks in healthy aging: a MEG study

The proportion of elderly people in the population has increased rapidly in the last century and consequently "healthy aging" is expected to become a critical area of research in neuroscience. Evidence reveals how healthy aging depends on three main behavioral factors: social lifestyle, cognitive activity and physical activity. In this study, we focused on the role of cognitive activity, concentrating specifically on educational and occupational attainment factors, which were considered two of the main pillars of cognitive reserve. 21 subjects with similar rates of social lifestyle, physical and cognitive activity were selected from a sample of 55 healthy adults. These subjects were divided into two groups according to their level of cognitive reserve; one group comprised subjects with high cognitive reserve (9 members) and the other contained those with low cognitive reserve (12 members). To evaluate the cortical brain connectivity network, all participants were recorded by Magnetoencephalography (MEG) while they performed a memory task (modified version of the Sternberg¿s Task). We then applied two algorithms (Phase Locking Value & Phase-Lag Index) to study the dynamics of functional connectivity. In response to the same task, the subjects with lower cognitive reserve presented higher functional connectivity than those with higher cognitive reserve. These results may indicate that participants with low cognitive reserve needed a greater 'effort' than those with high cognitive reserve to achieve the same level of cognitive performance. Therefore, we conclude that cognitive reserve contributes to the modulation of the functional connectivity patterns of the aging brain.

The immature state of the Odonata ... / by Louis Cabot.

v.8:no.1 (1881)

The immature state of the Odonata ... / by Louis Cabot.

no.5 (1872)

Student notebook of Marston Cabot, ca. 1720-1735

This leather-bound volume contains excerpts copied by Marston Cabot from books he read while he was a student at Harvard in 1723. The volume includes extracts from Charles Morton's 1687 Compendium Physicae (titled "of Phisicks" by Cabot), Dr. Adriani Heereboord (Adrianus Heereboord), Philosophia Naturalis and Johanne-Henrico Alstedio’s (John Henry Alsted) geometry text Compendium Geometria. The excerpts from Compendium Geometria include both figures and text, primarily in Latin with some Greek. The volume also includes “Theses quaedam extractae potissimum ex Enchiridio Metaphysico Domini Johannis Clerici" a précis of Jean Le Clerc's Ontologia et Pneumatologia made by Jonathan Remington, a Harvard Tutor from 1703 to 1711, to serve in place of printed textbooks. The names Jonathan Jackson and Edward Jackson are written on the inside cover, suggesting the book may have been handed down to Edward Jackson (Class of 1726) and his son Jonathan Jackson (Class of 1761). The text of the volume is in Marston Cabot's hand.

John and Sebastian Cabot; the discovery of North America,

Mode of access: Internet.

Poems and dramas of George Cabot Lodge.

Mode of access: Internet.

Viaje pintoresco á las dos Américas, Asia y África : resúmen jeneral de los viajes y descubrimientos de Colon, Magallanes, Las Casas, Gomara, La Condamine, Ulloa, Jorge Juan, Humboldt, Molina, Cabot, Grijalva, Koempfer, Marco Polo, Forster, Chardin, Tournefort, Volney, In Loubére, Chateaubriand, Caillé, Lander, etc., etc. /

Mode of access: Internet.

A Pápai reformáta szent ekklésiának rövid históriája : mellyet a' reformatziótól fogva e' mai időkig le-hozva meg. irt /

Mode of access: Internet.

A discourse delivered in the Stone church, Summer-street, the Lord's day after the interment of the Hon. George Cabot : who died April 18th 1823 /

Caption title: Sermon at the New South, on the death of the Hon. George Cabot.

Magyar nyelv-tanitó könyv; melyly a' magyar beszédnek, és irásnak szabásait meg-itélve, gántsolva, és meg-választva adja-elé.

Mode of access: Internet.

Little Meg's children /

Mode of access: Internet.