What checkers actually check: an eye tracking study of inhibitory control and working memory

<p>Background - Not only is compulsive checking the most common symptom in Obsessive Compulsive Disorder (OCD) with an estimated prevalence of 50–80% in patients, but approximately ~15% of the general population reveal subclinical checking tendencies that impact negatively on their performance in daily activities. Therefore, it is critical to understand how checking affects attention and memory in clinical as well as subclinical checkers. Eye fixations are commonly used as indicators for the distribution of attention but research in OCD has revealed mixed results at best.</p> <p>Methodology/Principal Finding - Here we report atypical eye movement patterns in subclinical checkers during an ecologically valid working memory (WM) manipulation. Our key manipulation was to present an intermediate probe during the delay period of the memory task, explicitly asking for the location of a letter, which, however, had not been part of the encoding set (i.e., misleading participants). Using eye movement measures we now provide evidence that high checkers’ inhibitory impairments for misleading information results in them checking the contents of WM in an atypical manner. Checkers fixate more often and for longer when misleading information is presented than non-checkers. Specifically, checkers spend more time checking stimulus locations as well as locations that had actually been empty during encoding.</p> <p>Conclusions/Significance - We conclude that these atypical eye movement patterns directly reflect internal checking of memory contents and we discuss the implications of our findings for the interpretation of behavioural and neuropsychological data. In addition our results highlight the importance of ecologically valid methodology for revealing the impact of detrimental attention and memory checking on eye movement patterns.</p&gt

Firm survival: The role of incubators and business characteristics

This paper analyzes the impact of business incubators on firm survival. Using a configurational comparative method, namely fuzzy-set qualitative comparative analysis (fsQCA), the article also examines whether degree of business innovation, size, sector, and export activity affects firm survival. Results show that, when combined with other variables (i.e. sector, technology), business size is a sufficient condition for firm survival. Likewise, incubators alone cannot affect survival. A combination between incubators and other factors is necessary to ensure firm survival.Mas Verdú, F.; Ribeiro Soriano, D.; Roig Tierno, H. (2015). Firm survival: The role of incubators and business characteristics. Journal of Business Research. 68(4):793-796. doi:10.1016/j.jbusres.2014.11.030S79379668

Low-rank updates of balanced incomplete factorization preconditioners

[EN] Let Ax = b be a large and sparse system of linear equations where A is a nonsingular matrix. An approximate solution is frequently obtained by applying preconditioned terations. Consider the matrix B = A + PQT where P,Q ∈ Rn×k are full rank matrices. In this work, we study the problem of updating a previously computed preconditioner for A in order to solve the updated linear system Bx = b by preconditioned iterations. In particular, we propose a method for updating a Balanced Incomplete Factorization preconditioner. The strategy is based on the computation of an approximate Inverse Sherman-Morrison decomposition for an equivalent augmented linear system. Approximation properties of the preconditioned matrix and an analysis of the computational cost of the algorithm are studied. Moreover the results of the numerical experiments with different types of problems show that the proposed method contributes to accelerate the convergence.This work was supported by the Spanish Ministerio de Economia y Competitividad under grant MTM2014-58159-P.Cerdán Soriano, JM.; Marín Mateos-Aparicio, J.; Mas Marí, J. (2017). Low-rank updates of balanced incomplete factorization preconditioners. Numerical Algorithms. 74(2):337-370. https://doi.org/10.1007/s11075-016-0151-6S337370742Bellavia, S., Bertaccini, D., Morini, B.: Nonsymmetric preconditioner updates in Newton-Krylov methods for nonlinear systems. SIAM J. Sci. Comput. 33 (5), 2595–2619 (2011)Benzi, M., Bertaccini, D.: Approximate inverse preconditioning for shifted linear systems. BIT 43(2), 231–244 (2003)Bergamaschi, L., Bru, R., Martínez, A.: Low-rank update of preconditioners for the inexact Newton method with SPD Jacobian. Math. Comput. Model. 54, 1863–1873 (2011)Bergamaschi, L., Bru, R., Martínez, A., Mas, J., Putti, M.: Low-rank update of preconditioners for the nonlinear Richards Equation. Math. Comput. Model. 57, 1933–1941 (2013)Bergamaschi, L., Gondzio, J., Venturin, M., Zilli, G.: Inexact constraint preconditioners for linear systems arising in interior point methods. Comput. Optim. Appl. 36(2-3), 137–147 (2007)Beroiz, M., Hagstrom, T., Lau, S.R., Price, R.H.: Multidomain, sparse, spectral-tau method for helically symmetric flow. Comput. Fluids 102(0), 250–265 (2014)Bertaccini, D.: Efficient preconditioning for sequences of parametric complex symmetric linear systems. Electron. Trans. Numer. Anal. 18, 49–64 (2004)Bollhöfer, M.: A robust and efficient ILU that incorporates the growth of the inverse triangular factors. SIAM J. Sci. Comput. 25(1), 86–103 (2003)Bollhöfer, M., Saad, Y.: On the relations between ILUs and factored approximate inverses. SIAM. J. Matrix Anal. Appl. 24(1), 219–237 (2002)Bru, R., Cerdán, J., Marín, J., Mas, J.: Preconditioning sparse nonsymmetric linear systems with the Sherman-Morrison formula. SIAM J. Sci. Comput. 25(2), 701–715 (2003)Bru, R., Marín, J., Mas, J., Tůma, M.: Balanced incomplete factorization. SIAM J. Sci. Comput. 30(5), 2302–2318 (2008)Bru, R., Marín, J., Mas, J., Tůma, M.: Improved balanced incomplete factorization. SIAM J. Matrix Anal. Appl. 31(5), 2431–2452 (2010)Cerdán, J., Faraj, T., Malla, N., Marín, J., Mas, J.: Block approximate inverse preconditioners for sparse nonsymmetric linear systems. Electron. Trans. Numer. Anal. 37, 23–40 (2010)Cerdán, J., Marín, J., Mas, J., Tůma, M.: Block balanced incomplete factorization. Technical Report No. TR-IMM2015/04, Polytechnic University of Valencia, Spain (2015)Davis, T.A.: University of Florida Sparse Matrix Collection. available online at http://www.cise.ufl.edu/~davis/sparse/ , NA Digest, vol. 94, issue 42, October 1994.Tebbens, J.D., Tůma, M.: Efficient preconditioning of sequences of nonsymmetric linear systems. SIAM J. Sci Comput. 29(5), 1918–1941 (2007)Tebbens, J.D., Tůma, M.: Preconditioner updates for solving sequences of linear systems in matrix-free environment. Numer Linear Algebra Appl. 17, 997–1019 (2010)Embree, M., Sifuentes, J.A., Soodhalter, K.M., Szyld, D.B., Xue, F.: Short-term recurrence Krylov subspace methods for nearly hermitian matrices. SIAM.J. Matrix Anal. Appl. 33-2, 480–500 (2012)Engquist, B., Ying, L.: Sweeping preconditioner for the Helmholtz equation: hierarchical matrix representation. Commun. Pure Appl. Math. 64, 697–735 (2011)Gatto, P., Christiansen, R.E., Hesthaven, J.S.: A preconditioner based on a low-rank approximation with applications to topology optimization. Technical Report EPFL-ARTICLE-207108, École polytechnique fédérale de Lausanne, EPFL, CH-1015 Lausanne, 2015.Grasedyck, L., Hackbusch, W.: Construction and arithmetics of H-matrices. Computing 70(4), 295–334 (2003)Grasedyck, L., Kressner, D., Tobler, C.: A literature survey of low-rank tensor approximation techniques. GAMM-Mitteilungen 36(1), 53–78 (2013)Greengard, L., Rokhlin, V.: A new version of the fast multipole method for the Laplace equation in three dimensions. Acta Numer. 6(1), 229–269 (1997)Hager, W.W.: Updating the inverse of matrix. SIAM Rev. 31(2), 221–239 (1989)Halko, N., Martinsson, P.G., Tropp, J.A.: Finding structure with randomness: probabilistic algorithms for constructing approximate matrix decompositions. SIAM Rev. 53(2), 217–288 (2011)Kelley, C.T.: Solving Nonlinear Equations with Newton’s Method. Fundamentals of algorithms. Society for Industrial and Applied Mathematics (SIAM), Philadelphia (2003)Saad, Y.: ILUT: a dual threshold incomplete L U factorization. Numer. Linear Algebra Appl. 1(4), 387–402 (1994)Saad, Y., Schulz, M.H.: GMRES: a generalized minimal residual algorithm for solving nonsymmetric linear systems. SIAM J. Sci. Stat. Comput. 7, 856–869 (1986)Simoncini, V., Szyld, D.B.: The effect of non-optimal bases on the convergence of Krylov subspace methods. Numer Math. 100(4), 711–733 (2005)van der Vorst, H.A.: Bi-CGSTAB: a fast and smoothly converging variant of bi-CG for the solution of non-symmetric linear systems. SIAM J. Sci. Stat. Comput. 12, 631–644 (1992

A bibliometric overview of the Journal of Business Research

Abstract de la ponencia[EN] The Journal of Business Research is a leading international journal in business research dating back to 1973. This study analyzes all the publications in the journal since its creation by using a bibliometric approach. The objective is to provide a complete overview of the main factors that affect the journal. This analysis includes key issues such as the publication and citation structure of the journal, the most cited articles, and the leading authors, institutions, and countries in the journal. Unsurprisingly, the USA is the leading region in the journal although a considerable dispersion exists, especially during the last years when European and Asian universities are taking a more significant position.Merigó, J.; Mas-Tur, A.; Roig-Tierno, N.; Ribeiro-Soriano, D. (2016). A bibliometric overview of the Journal of Business Research. En CARMA 2016: 1st International Conference on Advanced Research Methods in Analytics. Editorial Universitat Politècnica de València. 148-148. https://doi.org/10.4995/CARMA2016.2015.423814814

A bibliometric overview of the Journal of Business Research

Abstract de la ponencia[EN] The Journal of Business Research is a leading international journal in business research dating back to 1973. This study analyzes all the publications in the journal since its creation by using a bibliometric approach. The objective is to provide a complete overview of the main factors that affect the journal. This analysis includes key issues such as the publication and citation structure of the journal, the most cited articles, and the leading authors, institutions, and countries in the journal. Unsurprisingly, the USA is the leading region in the journal although a considerable dispersion exists, especially during the last years when European and Asian universities are taking a more significant position.Merigó, J.; Mas-Tur, A.; Roig-Tierno, N.; Ribeiro-Soriano, D. (2016). A bibliometric overview of the Journal of Business Research. En CARMA 2016: 1st International Conference on Advanced Research Methods in Analytics. Editorial Universitat Politècnica de València. 148-148. https://doi.org/10.4995/CARMA2016.2015.423814814

Complexity changes in functional state dynamics suggest focal connectivity reductions

The past two decades have seen an explosion in the methods and directions of neuroscience research. Along with many others, complexity research has rapidly gained traction as both an independent research field and a valuable subdiscipline in computational neuroscience. In the past decade alone, several studies have suggested that psychiatric disorders affect the spatiotemporal complexity of both global and region-specific brain activity (Liu et al., 2013; Adhikari et al., 2017; Li et al., 2018). However, many of these studies have not accounted for the distributed nature of cognition in either the global or regional complexity estimates, which may lead to erroneous interpretations of both global and region-specific entropy estimates. To alleviate this concern, we propose a novel method for estimating complexity. This method relies upon projecting dynamic functional connectivity into a low-dimensional space which captures the distributed nature of brain activity. Dimension-specific entropy may be estimated within this space, which in turn allows for a rapid estimate of global signal complexity. Testing this method on a recently acquired obsessive-compulsive disorder dataset reveals substantial increases in the complexity of both global and dimension-specific activity versus healthy controls, suggesting that obsessive-compulsive patients may experience increased disorder in cognition. To probe the potential causes of this alteration, we estimate subject-level effective connectivity via a Hopf oscillator-based model dynamic model, the results of which suggest that obsessive-compulsive patients may experience abnormally high connectivity across a broad network in the cortex. These findings are broadly in line with results from previous studies, suggesting that this method is both robust and sensitive to group-level complexity alterations

Mapping Cortical and Subcortical Asymmetry in Obsessive-Compulsive Disorder: Findings From the ENIGMA Consortium

Background: Lateralized dysfunction has been suggested in obsessive-compulsive disorder (OCD). However, it is currently unclear whether OCD is characterized by abnormal patterns of brain structural asymmetry. Here we carried out what is by far the largest study of brain structural asymmetry in OCD. Methods: We studied a collection of 16 pediatric datasets (501 patients with OCD and 439 healthy control subjects), as well as 30 adult datasets (1777 patients and 1654 control subjects) from the OCD Working Group within the ENIGMA (Enhancing Neuro Imaging Genetics through Meta Analysis) Consortium. Asymmetries of the volumes of subcortical structures, and of measures of regional cortical thickness and surface areas, were assessed based on T1-weighted magnetic resonance imaging scans, using harmonized image analysis and quality control protocols. We investigated possible alterations of brain asymmetry in patients with OCD. We also explored potential associations of asymmetry with specific aspects of the disorder and medication status. Results: In the pediatric datasets, the largest case-control differences were observed for volume asymmetry of the thalamus (more leftward; Cohen's d = 0.19) and the pallidum (less leftward; d = -0.21). Additional analyses suggested putative links between these asymmetry patterns and medication status, OCD severity, or anxiety and depression comorbidities. No significant case-control differences were found in the adult datasets. Conclusions: The results suggest subtle changes of the average asymmetry of subcortical structures in pediatric OCD, which are not detectable in adults with the disorder. These findings may reflect altered neurodevelopmental processes in OCD

Neural Network Alterations Across Eating Disorders: A Narrative Review of fMRI Studies

Background: Functional magnetic resonance imaging (fMRI) has provided insight on how neural abnormalities are related to the symptomatology of the eating disorders (EDs): anorexia nervosa (AN), bulimia nervosa (BN), and binge eating disorder (BED). More specifically, an increasingly growing number of brain imaging studies has shed light on how functionally connected brain networks contribute not only to disturbed eating behavior, but also to transdiagnostic alterations in body/interoceptive perception, reward processing and executive functioning. Methods: This narrative review aims to summarize recent advances in fMRI studies of patients with EDs by highlighting studies investigating network alterations that are shared across EDs. Results and Conclusion: Findings on reward processing in both AN and BN patients point to the presence of altered sensitivity to salient food stimuli in striatal regions and to the possibility of hypothalamic inputs being overridden by top-down emotional-cognitive control regions. Additionally, innovative new lines of research suggest that increased activations in fronto-striatal circuits are strongly associated with the maintenance of restrictive eating habits in AN patients. Although significantly fewer studies have been carried out in patients with BN and BED, aberrant neural responses to both food cues and anticipated food receipt appear to occur in these populations. These altered responses, coupled with diminished recruitment of prefrontal cognitive control circuitry, are believed to contribute to the binge eating of palatable foods. Results from functional network connectivity studies are diverse, but findings tend to converge on indicating disrupted resting-state connectivity in executive networks, the default-mode network and the salience network across EDs