Genetic and environmental influences on the brain functional networks in older adults

As humans age, the functional organisation of their brain networks undergoes complex changes that are associated with observed changes in cognition. Both genetics and the environment play a crucial role in influencing changes in the network topology of the ageing brain. In addition, the network topology is influenced by age-related brain diseases. To date, there is a paucity of population-based studies investigating the contributions of age, genetic and environmental factors, and brain disease to the architecture of the functional brain networks. The broad aim of this thesis, therefore, was to examine the influence of genetics, environmental factors, and disease-states on functional brain networks in older individuals using the United Kingdom (UK) Biobank data (N~18,455; ages 44-80 years). To study functional brain networks, I modelled large-scale brain networks from resting-state functional magnetic resonance imaging (fMRI) scans using graph theory, defined by a collection of nodes (brain regions) and edges (magnitude of temporal correlation in activity on fMRI between two brain regions). Four studies are reported in the thesis. In the first study, I investigated the genetic determinants of functional brain networks. I first estimated single nucleotide polymorphism (SNP) heritability (h2). Subsequently, genome-wide association studies (GWAS) were performed to identify genetic variants associated with each graph theory measure. Gene-based association analysis was carried out to uncover gene-level associations, and the functional consequences of the significant genetic variants were explored. As brain reorganisation of the functional networks has been differentially observed with ageing in the two sexes, I examined in the second study how age and sex are associated with the topology of functional brain networks in association with cognitive performance. In the third study, I examined the association of sleep and other lifestyle factors such as exercise, alcohol, and smoking, with functional network properties. In the final study, I studied how disease phenotypes, in particular depressive symptoms, influence functional network properties. This thesis provides several novel contributions to the literature by identifying important genetic, environmental, and disease-related factors that are associated with measures of functional networks in the ageing brain. The findings highlight biological pathways relevant to the ageing human brain functional network integrity and diseases that affect it

Linking Research and Policy: Assessing a Framework for Organic Agricultural Support in Ireland

This paper links social science research and agricultural policy through an analysis of support for organic agriculture and food. Globally, sales of organic food have experienced 20% annual increases for the past two decades, and represent the fastest growing segment of the grocery market. Although consumer interest has increased, farmers are not keeping up with demand. This is partly due to a lack of political support provided to farmers in their transition from conventional to organic production. Support policies vary by country and in some nations, such as the US, vary by state/province. There have been few attempts to document the types of support currently in place. This research draws on an existing Framework tool to investigate regionally specific and relevant policy support available to organic farmers in Ireland. This exploratory study develops a case study of Ireland within the framework of ten key categories of organic agricultural support: leadership, policy, research, technical support, financial support, marketing and promotion, education and information, consumer issues, inter-agency activities, and future developments. Data from the Irish Department of Agriculture, Fisheries and Food, the Irish Agriculture and Food Development Authority (Teagasc), and other governmental and semi-governmental agencies provide the basis for an assessment of support in each category. Assessments are based on the number of activities, availability of information to farmers, and attention from governmental personnel for each of the ten categories. This policy framework is a valuable tool for farmers, researchers, state agencies, and citizen groups seeking to document existing types of organic agricultural support and discover policy areas which deserve more attention

Aerospace medicine and biology: A continuing bibliography with indexes (supplement 406)

This bibliography lists 346 reports, articles and other documents introduced into the NASA Scientific and Technical Information System during Oct. 1995. Subject coverage includes: aerospace medicine and physiology, life support systems and man/system technology, protective clothing, exobiology and extraterrestrial life, planetary biology, and flight crew behavior and performance

Applying safe flooring in housing environments related to the independent elderly : evaluating suitability flooring technology to absorb impact in the event of a fall

Aplicat embargament des de la data de defensa fins el dia 3/6/2022This research has been developed with the intention of investigating a different generation of pavements. Most of the current pavements have the same basic standard characteristics and this ensures that living conditions are comfortable, safe, and pleasant for the majority of citizens. But a small group of pavements is designed with a specific purpose: to reduce injuries related to people's falls to the ground; They are called CF (compliant flooring in English). A detailed study of CF flooring systems is warranted to assess their usability for vulnerable groups such as the elderly. This study is structured in six chapters. The first chapter has dealt mainly with bibliographic studies and statistical data consulted on official and international websites. This section evaluates the importance of the increase in the elderly population, life expectancy, and threats to the safety and health of the elderly, especially, and their secondary effects. The scope of the research has been carried out internationally, in Europe and within Spain, and finally, specifically for Catalonia. The second chapter presents a brief overview of the interior flooring, specifically considering its comfort and safety during use. The importance and direct relationship between the sole of the foot and the gait mechanism with respect to the type of pavement have been verified. Many factors that influence this have been investigated, such as the physics and biomechanics of the body when walking, the kinematics of falls, and the dynamics of impact. In addition, a general description of the behavior of materials for use in pavements has been made to better understand the behavior of CF systems. In addition, the most suitable strategies to cope with falls and reduce injuries are discussed. Examining other products with appreciable energy-absorbing and shock-reducing capabilities has been helpful in the proposed pre-designs, all of which have been made based on numerical analysis and related standards. The third chapter is already dedicated to the study of technology and research on the most suitable CF systems; studies from academic, commercial, and architecture departments, in general, are included. In this section, some standard tests related to the various selected materials are developed and several examples of similar products are studied. The fourth chapter includes field research (on-site) and analysis of case studies. Several notable flooring companies around the world were contacted by mail, specifically examining those products whose manufacturers claimed to be shock absorbers. This part of the investigation was slowed down by the delay in shipments. Once they arrived, a real environment was sought where they could obtain the opinion of the elderly and the personnel assigned to their care. All the practice tests were carried out in a residence for the elderly in Barcelona for about two months, focusing on the study of the current pavements of the center and the current derived problems related to users.This entire process was completed by interviewing users and caregivers with predefined questionnaires. It should be noted that this allowed us to contrast the quantitative characteristics of the study in combination with the elements of qualitative research. Chapter Five deals with the results, discussions, suggestions for installation and improvement of pavement safety in risk areas. Simulations were also carried out on a possible base structure of the pavements with the finite element method (FEM). Chapter six presents guidelines for future developments. The author further investigated the materials and their structure and is presented them as a basis for future technical developments.The author considers that, with more detailed studies, it would be possible to use as CF system other materials, either natural or recycled based on agricultural products, which would increase the diversity of the CF system offer and promote more sustainable architectureEsta investigación se ha desarrollado con la intención de investigar una generación diferente de pavimentos. La mayoría de los actuales pavimentos tienen las mismas características básicas estándar y ello garantiza que las condiciones de vida sean cómodas, seguras y agradables para la mayoría de los ciudadanos. Pero un grupo reducido de pavimentos está diseñado con un propósito específico: reducir las lesiones relacionadas con las caídas al suelo de las personas; son los denominados CF (compliant flooring en inglés). Un estudio detallado de los sistemas de pavimentos CF está justificado para evaluar su posibilidad de uso para grupos vulnerables como los ancianos. Este estudio se estructura en seis capítulos. En el primer capítulo se han abordado principalmente los estudios bibliográficos y datos estadísticos consultados en sitios web oficiales e internacionales. En esta sección se evalúa la importancia del aumento de la población anciana. El ámbito de la investigación se ha realizado a nivel internacional, en Europa y dentro de España, y finalmente, específicamente para Cataluña. El segundo capítulo se presenta una breve panorámica del pavimento interior. Se ha constatado la importancia y relación directa entre la planta del pie y el mecanismo de andar con respecto al tipo de pavimento. Se han investigado muchos factores que influyen en ello. Además, se ha realizado una descripción general del comportamiento de los materiales al uso en pavimentos para comprender mejor el comportamiento de los sistemas de CF. Además, se discuten las estrategias más idóneas para hacer frente a las caídas y reducir las lesiones. Examinar otros productos con apreciables capacidades de amortiguación de energía y reducción de impactos ha sido de gran ayuda en los prediseños propuestos, todos los cuales se han realizado sobre la base de análisis numérico y los estándares relacionados. El tercer capítulo está dedicado ya al estudio de la tecnología y la investigación sobre los sistemas de C más idóneos; se incluyen estudios procedentes de departamentos académicos, comerciales y de arquitectura en general. En esta sección se desarrollan algunas pruebas estándar relacionadas con los diversos materiales seleccionados y se estudian varios ejemplos de productos similares. El cuarto capítulo incluye investigación de campo (in situ) y análisis de estudios de casos. Se contactó por correo con varias empresas notables de pavimentos en todo el mundo, y se examinaron específicamente aquellos productos cuyos fabricantes afirmaban ser amortiguadores. Esta parte de la investigación se vio ralentizada por la demora en los envíos. Una vez llegados se buscó un ámbito real donde poder recabar la opinión de las personas mayores y del personal adscrito a su cuidado. Todas las pruebas prácticas se realizaron en una residencia de ancianos de Barcelona durante unos dos meses, centrándose en el estudio de los actuales pavimentos del centro y los problemas actuales derivados relacionados con los usuarios. Todo este proceso se completó mediante entrevistas a usuarios y cuidadores con cuestionarios predefinidos. El Capítulo Cinco se refiere a los resultados, discusiones, sugerencias para la instalación y mejora de la seguridad del pavimento en áreas de riesgo. También se realizaron simulaciones sobre una posible estructura base de los pavimentos con el método elemento finito (FEM). El capítulo seis presenta directrices para desarrollos futuros. El autor investigó más a fondo sobre los materiales y su estructura, y se presenta como una base para desarrollos técnicos futuros. El autor considera que, con estudios más detallados, sería posible utilizar como CF otros materiales, bien naturales o reciclados a base de productos agrícolas, lo cual aumentaría la diversidad de la oferta de CF y fomentaría la arquitectura más sostenible.Postprint (published version

Detection of microsleeps from the eeg via optimized classification techniques.

Microsleeps are complete breaks in responsiveness for 0.5–15 s. They can lead to multiple fatalities in certain occupational fields (e.g., transportation and military) due to the need in such occupations for extended and continuous vigilance. Therefore, an automated microsleep detection system may assist in the reduction of poor job performance and occupational fatalities. An EEG-based microsleep detector offers advantages over a videobased microsleep detector, including speed and temporal resolution. A series of software modules were implemented to examine different feature sets to determine the optimal circumstances for automated EEG-based microsleep detection. The microsleep detection system was organized in a similar manner to an EEG-based brain-computer interface (BCI). EEG data underwent baseline removal and filtering to remove overhead noise. Following this, feature extraction generated spectral features based upon an estimate of the power spectrum or its logarithmic transform. Following this, feature selection/reduction (FS/R) was used to select the most relevant information across all the spectral features. A trained classifier was then tested on data from a subject it had not seen before. In certain cases, an ensemble of classifiers was used instead of a single classifier. The performance measures from all cases were then averaged together in leave-one-out crossvalidation (LOOCV). Sets of artificial data were generated to test a prototype EEG-based microsleep detection system, consisting of a combination of EEG and 2-s bursts of 15 Hz sinusoids of varied signal-to-noise ratios (SNRs) ranging from 16 down to 0.03. The balance between events and non-events was varied between evenly balanced and highly imbalanced (e.g., events occurring only 2% of the time). Features were spectral estimates of various EEG bands (e.g., alpha band power) or ratios between them. A total of 34 features for each of the 16 channels yielded a total of 544 features. Five minutes of EEG from eight subjects were used in the generation of the dummy data, and each subject yielded a matrix of 300 observations of 544 features. Datasets from two prior microsleep studies were employed after validating the system on the artificial data. The first, Study A (N = 8), had 16 channels sampled at 256 Hz from two 1-hour sessions per subject and the second, Study C (N = 10), had one 50-min session with 30-62 channels per subject sampled at 250 Hz. A vector of 34 spectral features from each channel was concatenated into a feature vector for each 2-s interval, with each interval having a 1-s overlap with the prior one. In both cases, microsleeps had been identified via a combination of video recording and performance on a continuous tracking task. Study A provided four datasets to compare effects of various preprocessing techniques on performance: (1) Study A bipolar EEG with Independent Component Analysis (ICA) preprocessing and artefact pruning (total automated rejection of artefact-containing epochs) and logarithmic transforms of the spectral features (SABIL); (2) Study A bipolar EEG with ICA-based eye blink removal and artefact removal with pruning of epochs with major artefacts, and linear spectral features (SABIS); (3) Study A referential EEG unprocessed by ICA with spectral features (SARUS); and (4) Study A bipolar EEG unprocessed by ICA with spectral features (SABUS). The second study had one primary feature set, the Study C referential EEG ICA preprocessed spectral feature (SCRIS) variant. LOOCV was evaluated based on the phi correlation coefficient. After replicating prior work, several FS/R and classifier structures were investigated with both the artificially balanced and unbalanced data. Feature selection/reduction methods included principal component analysis (PCA), common spatial patterns (CSP), projection to latent structures (PLS), a new method based on average distance between events and nonevents (ADEN), ADEN normalized with a z-score transform (ADENZ), genetic algorithms in concert with ADEN (GADEN), and genetic algorithms in concert with ADENZ (GADENZ). Several pattern recognition algorithms were investigated: linear discriminant analysis (LDA), radial basis functions (RBFs), and Support Vector Machines with Gaussian (SVMG) and polynomial (SVMP) kernels. Classifier structures examined included single classifiers, bagging, boosting, stacking, and adaptive boosting (AdaBoost). The highest LOOCV results on artificial data (SNR = 0.3) corresponded to GADEN with 10 features and a single LDA classifier with a mean phi value of 0.96. Of the four Study A datasets, PCA with 150 features and a stacking ensemble achieved the highest mean phi of 0.40 with the SABIL feature set, and ADEN with 20 features with a single LDA classifier achieved the highest mean phi of 0.10 with Study C. Other machine-learning methodologies, such as training on artificially balanced data, decreasing the training size, within-subject training and testing, and randomly mixed data from across subjects, were also examined. Training on artificially balanced data did not improve performance. An issue found by performing within-subject training and testing was that, for certain subjects, a classifier trained on one-half of the subject’s data and then tested on the other half was that classifier performance dropped to random guessing. The low phi values on within-subject tests occurred independently of the feature selection/reduction method explored. As such, performance of a standard LOOCV was often dependent on whether a particular testing subject had a low (< 0.15) within-subjects mean phi correlation coefficient. Training on only the higher mean phi values did not boost performance. Additional tests found correlations (r = 0.57, p = 0.003 for Study A and r = 0.67, p 0.15) and longer mean microsleep durations. Other individual subject characteristics, such as number of microsleeps and subject age, did not have significant differences. The primary findings highlighted the strengths and limitations of supervised feature selection and linear classifiers trained upon highly variable between-subject features across two studies. Findings suggested that a classifier performs best when individuals have high mean microsleep durations. On the configurations investigated, preprocessing factors, such as ICA preprocessing, feature extraction method, and artefact pruning, affected the performance more than changing specific module configurations. No significant differences between the SABIL features and the lower performing Study A feature sets were found due to overlapping ranges of performance (p = 0.15). The findings suggest that the investigated techniques plateaued in performance on the Study A data, reaching a point of diminishing returns without fundamentally changing the nature of the classification problem. The different number of channels of varying quality across all subjects in Study C rendered microsleep classification extremely difficult, but even a linear classifier can properly generalize if exposed to a large enough variety of data from across the entire set. Many of the techniques explored are also relevant to other fields, such as braincomputer interface (BCI) and machine learning