Fast Scalable and Accurate Discovery of DAGs Using the Best Order Score Search and Grow-Shrink Trees

Learning graphical conditional independence structures is an important machine learning problem and a cornerstone of causal discovery. However, the accuracy and execution time of learning algorithms generally struggle to scale to problems with hundreds of highly connected variables -- for instance, recovering brain networks from fMRI data. We introduce the best order score search (BOSS) and grow-shrink trees (GSTs) for learning directed acyclic graphs (DAGs) in this paradigm. BOSS greedily searches over permutations of variables, using GSTs to construct and score DAGs from permutations. GSTs efficiently cache scores to eliminate redundant calculations. BOSS achieves state-of-the-art performance in accuracy and execution time, comparing favorably to a variety of combinatorial and gradient-based learning algorithms under a broad range of conditions. To demonstrate its practicality, we apply BOSS to two sets of resting-state fMRI data: simulated data with pseudo-empirical noise distributions derived from randomized empirical fMRI cortical signals and clinical data from 3T fMRI scans processed into cortical parcels. BOSS is available for use within the TETRAD project which includes Python and R wrappers

Modelo operativo para el comité de operaciones de emergencia del cantón Guayaquil ante un evento adverso de gran magnitud.

Este documento contiene archivo en PDF.El cantón Guayaquil, está localizado en una de las regiones más sísmicas del mundo denominada Cinturón de Fuego, frente a la placa tectónica de Nazca, que choca contra la placa Sudamericana y muy próximo, a una serie de fallas geológicas, y por el uso inadecuado del suelo y el tipo de construcción, lo convierten en un lugar muy expuesto ante este fenómeno natural.Las autoridades, deben velar el bienestar urbano ante los riesgos naturales o antrópicos, ejerciendo la Gestión de Riesgos amparados en el marco legal vigente, como leyes constitucionales, convenios internacionales, reglamentos de ley, resoluciones del ente rector, ordenanzas municipales, protocolos, planes de acción y manuales institucionales. Este trabajo, pretende contribuir con la definición de funciones e interrelación, para que los responsables de cada segmento de las tres áreas del Comité de Operaciones de Emergencias del Cantón de Guayaquil lo consideren como viable y puedan aplicarlo y entonces con sus actuaciones y/o decisiones, previas y posteriores a un evento adverso, logren reducir al máximo la vulnerabilidad. En el área de operaciones se ha recomendado que mínimo se deben crear 7 mesas de trabajo técnico y no solo soportar la primera respuesta del impacto del evento adverso, sino llegar a planificar con las mesas sectoriales temáticas, el plan de Recuperación a Mediano y Largo plazo.Estas mesas deberán estar coordinadas por una mesa central que consolide la información y haga el seguimiento respectivo; en el caso del cantón Guayaquil, la Dirección de Gestión de Riesgos deberá realizar esta labor.Para ello, se han consultado fuentes primarias y secundarias que provienen de actores y/o instituciones nacionales e internacionales especializadas o participantes de un COE Cantonal y los aportes del autor en el campo práctico.The city of Guayaquil, Ecuador, is located in one of the most seismically-active areas of the world—the Pacific Ring of Fire—where the Nazca and South America tectonic plates collide. Guayaquil is also close to a series of geological fault lines; this, coupled with inappropriate land use and construction methods, increases the city’s vulnerability to earthquakes. City authorities must keep the well-being and safety of urban populations at the forefront of planning for natural and man-made hazards. As such, disaster risk reduction is an important approach to incorporate, one that obligates the support of the existing legal framework—including international agreements, constitutional laws and regulations, ministerial resolutions, and municipal ordinances, protocols, and action plans—as well as clear institutional guidance. This paper aims to contribute to the improved organization and implementation of the three areas of the City of Guayaquil’s Emergency Operations Center (EOC)—information management, EOC operations, and political decision-making—through better defining functions and responsibilities and therein reducing vulnerability prior to and following an adverse event. As a first step, this paper proposes the creation of at least seven technical working groups, which will both support emergency first response and plan for medium- and long-term recovery. A central body will coordinate and consolidate the information from the technical working groups, including any relevant follow up. In Guayaquil Canton the Risk Management Division will act as the central organizing body. The author has consulted primary and secondary sources, including members of Guayaquil’s EOC and specialized national and international entities and institutions, as well as drawn on his own experience as a disaster risk management specialist

Deficits in visual system functional connectivity after blast-related mild TBI are associated with injury severity and executive dysfunction

INTRODUCTION: Approximately, 275,000 American service members deployed to Iraq or Afghanistan have sustained a mild traumatic brain injury (mTBI), with 75% of these incidents involving an explosive blast. Visual processing problems and cognitive dysfunction are common complaints following blast‐related mTBI. METHODS: In 127 veterans, we examined resting fMRI functional connectivity (FC) of four key nodes within the visual system: lateral geniculate nucleus (LGN), primary visual cortex (V1), lateral occipital gyrus (LO), and fusiform gyrus (FG). Regression analyses were performed (i) to obtain correlations between time‐series from each seed and all voxels in the brain, and (ii) to identify brain regions in which FC variability was related to blast mTBI severity. Blast‐related mTBI severity was quantified as the sum of the severity scores assigned to each of the three most significant blast‐related injuries self‐reported by subjects. Correlations between FC and performance on executive functioning tasks were performed across participants with available behavioral data (n = 94). RESULTS: Greater blast mTBI severity scores were associated with lower FC between: (A) LGN seed and (i) medial frontal gyrus, (ii) lingual gyrus, and (iii) right ventral anterior nucleus of thalamus; (B) V1 seed and precuneus; (C) LO seed and middle and superior frontal gyri; (D) FG seed and (i) superior and medial frontal gyrus, and (ii) left middle frontal gyrus. Finally, lower FC between visual network regions and frontal cortical regions predicted worse performance on the WAIS digit‐symbol coding task. CONCLUSION: These are the first published results that directly illustrate the relationship between blast‐related mTBI severity, visual pathway neural networks, and executive dysfunction – results that highlight the detrimental relationship between blast‐related brain injury and the integration of visual sensory input and executive processes

Individual and contextual factors associated with tobacco, alcohol, and cannabis use among Chilean adolescents: A multilevel study.

We studied the association between individual and contextual variables and the use of tobacco, alcohol, or cannabis in the last 30 days preceding the study, considering the hierarchical nature of students nested in schools. We used the 7th Chilean National School Survey of Substance Use (2007) covering 45,273 students (aged 12-21 years old) along with information from 1465 schools provided by the Chilean Ministry of Education. Multilevel univariable and multivariable logistic regression models were performed. We found a significant intra-class correlation within schools for all substances in the study. Common (e.g., availability of pocket money, more time spent with friends, poor parental monitoring, poor school bonding, bullying others, and lower risk perception of substance use) and unique predictors (e.g., school achievement on national tests) were identified. These findings may help in planning and conducting preventive interventions to reduce substance use

Oculomotor atypicalities in Developmental Coordination Disorder

Children with Developmental Coordination Disorder (DCD) fail to acquire adequate motor skill, yet surprisingly little is known about the oculomotor system in DCD. Successful completion of motor tasks is supported by accurate visual feedback. The purpose of this study was to determine whether any oculomotor differences can distinguish between children with and without a motor impairment. Using eye tracking technology, visual fixation, smooth pursuit, and pro- and anti-saccade performance were assessed in 77 children that formed three groups: children with DCD (aged 7–10), chronologically age (CA) matched peers, and a motor-match (MM) group (aged 4–7). Pursuit gain and response preparation in the pro- and anti-saccade tasks were comparable across groups. Compared to age controls, children with DCD had deficits in maintaining engagement in the fixation and pursuit tasks, and made more anti-saccade errors. The two typically developing groups performed similarly, except on the fast speed smooth pursuit and antisaccade tasks, where the CA group outperformed the younger MM group. The findings suggest that children with DCD have problems with saccadic inhibition and maintaining attention on a visual target. Developmental patterns were evident in the typically developing groups, suggesting that the pursuit system and cognitive control develop with age. This study adds to the literature by being the first to systematically identify specific oculomotor differences between children with and without a motor impairment. Further examination of oculomotor control may help to identify underlying processes contributing to DCD

Altered Small-World Brain Networks in Schizophrenia Patients during Working Memory Performance

Impairment of working memory (WM) performance in schizophrenia patients (SZ) is well-established. Compared to healthy controls (HC), SZ patients show aberrant blood oxygen level dependent (BOLD) activations and disrupted functional connectivity during WM performance. In this study, we examined the small-world network metrics computed from functional magnetic resonance imaging (fMRI) data collected as 35 HC and 35 SZ performed a Sternberg Item Recognition Paradigm (SIRP) at three WM load levels. Functional connectivity networks were built by calculating the partial correlation on preprocessed time courses of BOLD signal between task-related brain regions of interest (ROIs) defined by group independent component analysis (ICA). The networks were then thresholded within the small-world regime, resulting in undirected binarized small-world networks at different working memory loads. Our results showed: 1) at the medium WM load level, the networks in SZ showed a lower clustering coefficient and less local efficiency compared with HC; 2) in SZ, most network measures altered significantly as the WM load level increased from low to medium and from medium to high, while the network metrics were relatively stable in HC at different WM loads; and 3) the altered structure at medium WM load in SZ was related to their performance during the task, with longer reaction time related to lower clustering coefficient and lower local efficiency. These findings suggest brain connectivity in patients with SZ was more diffuse and less strongly linked locally in functional network at intermediate level of WM when compared to HC. SZ show distinctly inefficient and variable network structures in response to WM load increase, comparing to stable highly clustered network topologies in HC

Multi-echo fMRI, resting-state connectivity, and high psychometric schizotypy

Disrupted striatal functional connectivity is proposed to play a critical role in the development of psychotic symptoms. Previous resting-state functional magnetic resonance imaging (rs-fMRI) studies typically reported disrupted striatal connectivity in patients with psychosis and in individuals at clinical and genetic high risk of the disorder relative to healthy controls. This has not been widely studied in healthy individuals with subclinical psychotic-like experiences (schizotypy). Here we applied the emerging technology of multi-echo rs-fMRI to examine corticostriatal connectivity in this group, which is thought to drastically maximize physiological noise removal and increase BOLD contrast-to-noise ratio. Multi-echo rs-fMRI data (echo times, 12, 28, 44, 60 ms) were acquired from healthy individuals with low (LS, n = 20) and high (HS, n = 19) positive schizotypy as determined with the Oxford-Liverpool Inventory of Feelings and Experiences (O-LIFE). After preprocessing to ensure optimal contrast and removal of non-BOLD signal components, whole-brain functional connectivity from six striatal seeds was compared between the HS and LS groups. Effects were considered significant at clusterlevel p < .05 family-wise error correction. Compared to LS, HS subjects showed lower rs-fMRI connectivity between ventromedial prefrontal regions and ventral striatal regions. Lower connectivity was also observed between the dorsal putamen and the hippocampus, occipital regions, as well as the cerebellum. These results demonstrate that subclinical positive psychotic-like experiences in healthy individuals are associated with striatal hypoconnectivity as detected using multi-echo rs-fMRI. Further application of this approach may aid in characterizing functional connectivity abnormalities across the extended psychosis phenotype.Brain & Behavior Research Foundation NARSAD Young Investigator Gran