A generative flow for conditional sampling via optimal transport

Sampling conditional distributions is a fundamental task for Bayesian inference and density estimation. Generative models, such as normalizing flows and generative adversarial networks, characterize conditional distributions by learning a transport map that pushes forward a simple reference (e.g., a standard Gaussian) to a target distribution. While these approaches successfully describe many non-Gaussian problems, their performance is often limited by parametric bias and the reliability of gradient-based (adversarial) optimizers to learn these transformations. This work proposes a non-parametric generative model that iteratively maps reference samples to the target. The model uses block-triangular transport maps, whose components are shown to characterize conditionals of the target distribution. These maps arise from solving an optimal transport problem with a weighted $L^2$ cost function, thereby extending the data-driven approach in [Trigila and Tabak, 2016] for conditional sampling. The proposed approach is demonstrated on a two dimensional example and on a parameter inference problem involving nonlinear ODEs.Comment: 18 pages, 5 figure

Neural processing of criticism and positive comments from relatives in individuals with schizotypal personality traits

Objectives. High negative expressed emotion by family members towards schizophrenia patients increases the risk of subsequent relapse. The study aimed to determine whether individuals with high schizotypy (HS) and low schizotypy (LS) would differ in activation of brain areas involved in cognitive control when listening to relative criticism

Connectivity between mPFC and PCC predicts post‐choice attitude change: The self‐referential processing hypothesis of choice justification

Prior research shows that after making a choice, decision makers shift their attitudes in a choice‐congruous direction. Although this post‐choice attitude change effect is robust, the neural mechanisms underlying it are poorly understood. Here, we tested the hypothesis that decision makers elaborate on their choice in reference to self‐knowledge to justify the choice they have made. This self‐referential processing of the choice is thought to play a pivotal role in the post‐choice attitude change. Twenty‐four young American adults made a series of choices. They also rated their attitudes toward the choice options before and after the choices. In support of the current hypothesis, we found that changes in functional connectivity between two putative self‐regions (medial prefrontal cortex and posterior cingulate cortex/precuneus]) during the post‐choice (vs. pre‐choice) rating of the chosen options predicted the post‐choice shift of the attitudes toward the chosen options. This finding is the first to suggest that cognitive integration of various self‐relevant cognitions is instrumental in fostering post‐choice attitude change. Hum Brain Mapp 37:3810–3820, 2016. © 2016 Wiley Periodicals, Inc.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/134093/1/hbm23277_am.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/134093/2/hbm23277.pd

Effects of Temperature and Mobile Phase Condition on Chiral Recognition of Poly(l-phenylalanine) Chiral Stationary Phase

Characteristics of the chiral stationary phase with poly(l-phenylalanine) peptide selector, which was in α-helical state, was reported. Since environmental factors affect peptide conformation, the changes in enantioselectivity were examined depending on column temperature and mobile phase conditions (ionic strength, pH, mobile phase composition). Column temperature and pH drastically affected the enantioselectivity. Based on these changes, the relation between chiral recognition and secondary structure of the peptide selector was discussed. The column stability during sequential analysis under different separation conditions was also evaluated

Hör lek och lärande ihop? En studie om pedagogers resonemang och arbete kring det informella lek- lärandet i förskoleklassen

Syfte: Vårt syfte har varit att undersöka hur resonerar pedagoger kring det informella lek- lärandet och hur de arbetar med detta i förskoleklassen. Frågeställningar: -Vilka lekinslag förekommer i den planerade verksamheten/undervisningen? -Vem samspelar med vem? -Förkommer parallella lekaktiviteter i undervisningen? -Vilka planerade informella lärandesituationer förkommer? Metod: Studien har präglats av en kvalitativ undersökningsmetod där vi har använt oss av löpande observationer och semistrukturerade intervjuer. Studien har utförts i två ålderhomogena förskoleklasser och har koncentrerats till tre olika observationsepisoder. Vi har också kompletterat observationerna genom intervjuer med respektive lä- rare för förskoleklasserna. Vid observationerna användes observationsmall och vid intervjutillfällena användes bandspelare (diktafon). Resultat: I vår studie har vi märkt hur pedagogernas inställning till lärande har en avgörande roll för hur verksamheten utformas. Utifrån vårt resultat har vi kunnat se att pedagoger som anser att lek och lärande hör ihop också försö- ker att införa denna form av lärande i sin undervisning det vill säga informellt lek- lärande. De lekinslag och planerade informella lärandesituationer som har förkommit under observationerna har bland annat innehållit klosslek, sång och ramslek. Vi har även tagit del av en samlings aktivitet där barnens tidigare erfarenheter kring deras närmiljö har diskuterats och varit i fokus. Vi har funnit att parallella aktiviteter i undervisningen har för- kommit men dock i mindre utsträckning. I vår studie har samspelet mellan lärare ­ enskild elev varit i majoritet trots att aktiviteterna har utspelat sig i större elevgrupper

Application of the Shock Layer Theory to the Determination of the Mass Transfer Rate Coefficient and its Concentration Dependence for Proteins on Anion Exchange Columns

The extension of the shock layer theory to systems having a slow mass transfer kinetics and a concentration-dependent rate coefficient is discussed. Experiments were carried out with bovine serum albumin on two anion exchangers, TSK-GEL-DEAE-5PW and Resource-Q. The adsorption isotherm data, determined by single-step frontal analysis, could be fitted to simplified bi-Langmuir equations with very small residuals. A lumped kinetic model (solid film linear driving force model, with rate coefficient kf) was used to account for the mass transfer kinetics. The profile of each breakthrough curve (BC) was fitted to the curve calculated with this transport model and the rate coefficient kf obtained by identification. A linear dependence of kf on the average concentration of the step of the BC was found. The shock layer thicknesses (SLT) calculated for different relative concentrations agreed very well with the experimental results. This justifies the use of the SLT for the direct determination of rate coefficients

An analysis of self-referential processing and other aspects of emotional processing in healthy subjects and patients with affective disorders using functional magnetic resonance imaging

Emotionale Verarbeitung ist ein multidimensionaler Prozess, dessen kognitive Teilaspekte und entsprechende neuronale Korrelate mittels funktioneller agnetresonanztomographie (fMRT) dissoziiert werden können. In Studie 1 wird die angenommene enge Verknüpfung von selbstreferenzieller Verarbeitung (SRV) und episodischem Gedächtnisabruf (EGA) sowie deren gemeinsame und exklusive neuronale Repräsentation untersucht. Standardexperimentalaufgaben für SRV und EGA wurden in einem Experiment vereint und 29 Probanden mittels fMRT untersucht, so dass die Effekte von SRV und EGA kontrastiert und deren neuronale Korrelate dargestellt werden konnten. Bilder, die als selbstreferenziell eingestuft wurden, führten zu Anstiegen in den Blutsauerstoffgehalt-abhängigen (BOLD) Signalen (im Folgenden als „Aktivierungen“ bezeichnet) insbesondere im posterioren Cingulum (PCC), dem anterioren Praecuneus, dem medialen präfrontalen Cortex (MPFC) und inferioren Anteilen des Lobulus parietalis inferior. Im Gegensatz dazu waren bei der EGA Aktivierungen im posterioren Praecuneus, dem anterioren präfrontalen Cortex (aPFC), sowie superioren Anteilen des Lobulus parietalis inferior nachweisbar. Gemeinsame Aktivierungen von SRV und EGA fanden sich zwischen den zuvor erwähnten Regionen im Praecuneus und im inferioren Parietallappen, nicht jedoch im präfrontalen Cortex (PFC). Neben einem gemeinsam durch SRV und EGA aktivierten neuronalen Netzwerk im medialen und lateralen Parietallappen konnten durch Studie 1 drei funktionelle Unterteilungen im Vergleich SRV gegenüber EGA gezeigt werden: 1. eine anterior-posterior Unterteilung im medialen parietalen Cortex, 2. eine medial-anterolateral Unterteilung im PFC sowie 3. eine inferior-superior Unterteilung im lateralen parietalen Cortex. Studie 2 untersucht den Zusammenhang zwischen Aktivierung der Amygdala und Valenz der dargebotenen Stimuli bei hypomanischen und manischen bipolaren Patienten vor dem Hintergrund eines postulierten stimmungskongruenten Verarbeitungsbias bei der Manie. Die BOLD- Signale von 10 Patienten und 10 gesunden Kontrollpersonen bei der Betrachtung emotionaler Bilder wurden verglichen. Danach wurden die Bilder hinsichtlich ihrer Valenz und Intensität bewertet. Im Gegensatz zu gesunden Kontrollpersonen zeigten die Patienten nicht nur eine höhere Valenzbewertung positiver Bilder, sondern auch eine Mehraktivierung der linken Amygdala, die wiederum mit den Ergebnissen der „Young-Mania-Rating-Scale“ (YMRS) der Patienten korrelierte. Diese höheren Valenzbewertungen und gesteigerten Aktivierungen der Amygdala bei Betrachtung positiver emotionaler Bilder sind möglicherweise Ausdruck des postulierten positiven Verarbeitungsbias. Studie 3 untersucht die Aufmerksamkeitsmodulation bei der Verarbeitung emotionaler Bilder von Patienten mit Depression im Vergleich zu gesunden Kontrollprobanden, wobei im Rahmen der Depression eine verminderte Fähigkeit zur emotionalen Modulation angenommen wird. In einem fMRT-Experiment wurden Patienten und gesunden Kontrollpersonen emotionale Bilder mit und ohne Erwartungshinweis gezeigt. Während gesunde Probanden bei erwarteten im Gegensatz zu unerwarteten emotionalen Bildern eine Modulation mit herabgesetzter Aktivierung im dorsolateralen PFC (DLPFC) und gesteigerter Aktivierung im dorsomedialen PFC (DMPFC) zeigten, blieb diese bei Patienten mit Depression aus. Diese veränderte präfrontale Modulation könnte bei der Depression zur klinisch beobachtbaren verminderten emotionalen Modulationsfähigkeit beitragen.Emotional processing can be dissociated with functional magnetic resonance imaging (fMRI) into various cognitive functions and their corresponding neural correlates. Study 1 examines the functional overlap and dissociability of self-referential processing (SRP) and episodic memory retrieval (EMR). Standard tasks für SRP and EMR were combined into a single fMRI experiment involving 29 healthy subjects. The contrast of SRP- and EMR-related blood oxygen level dependent (BOLD) effects allowed a functional delineation of these processes. Stimuli judged as self-referential specifically activated the posterior cingulate/anterior precuneus, the medial prefrontal cortex and an inferior divison of the inferior parietal lobule while EMR specifically activated the posterior precuneus, the anterior prefrontal cortex and a superior division of the inferior parietal lobule. Overlapping activations were situated in the intermediate zones of the precuneus, the inferior parietal lobule, but not in the prefrontal cortex. Apart from common neuronal networks of SRP and EMR in the medial and lateral parietal cortex, three functional differentiations were observed: (1) an anterior-posterior differentiation in the medial parietal cortex, (2) a medial-anterolateral differentiation within the prefrontal cortex, (3) an inferior-superior differentiation within the lateral parietal cortex. Study 2 examines the relationship between amygdala activation and valence of the pictures presented in hypomanic and manic patients with fMRI. BOLD effects of 10 patients and 10 healthy control subjects viewing emotional pictures were contrasted. Following fMRI emotional valence and intensity were rated in a seperate session. Compared to healthy control subjects patients showed higher valence ratings in positive pictures and associated larger BOLD responses in the left amygdala that correlated with the patients Young Mania Rating Scale scores. Increased valence ratings and amygdala responses associated with positive picture viewing may reflect a postulated positive processing bias in mania. Study 3 examines the attentional modulation of patients with major depression compared to healthy control subjects in processing emotional pictures, postulating a reduced ability for emotional modulation in depression. fMRI BOLD effects of emotional picture viewing with and without emotional expectancy cue were contrasted. A modulation with reduced activation in the dorsolateral prefrontal cortex and enhanced activation in the dorsomedial prefrontal cortex was observed in healthy controls but not in patients with major depression. Altered prefrontal modulation may contribute to the impaired emotional modulation in major depression

Identifying controllable cortical neural markers with machine learning for adaptive deep brain stimulation in Parkinson's disease

Contains fulltext : 222474.pdf (publisher's version ) (Open Access)The identification of oscillatory neural markers of Parkinson's disease (PD) can contribute not only to the understanding of functional mechanisms of the disorder, but may also serve in adaptive deep brain stimulation (DBS) systems. These systems seek online adaptation of stimulation parameters in closed-loop as a function of neural markers, aiming at improving treatment's efficacy and reducing side effects. Typically, the identification of PD neural markers is based on group-level studies. Due to the heterogeneity of symptoms across patients, however, such group-level neural markers, like the beta band power of the subthalamic nucleus, are not present in every patient or not informative about every patient's motor state. Instead, individual neural markers may be preferable for providing a personalized solution for the adaptation of stimulation parameters. Fortunately, data-driven bottom-up approaches based on machine learning may be utilized. These approaches have been developed and applied successfully in the field of brain-computer interfaces with the goal of providing individuals with means of communication and control. In our contribution, we present results obtained with a novel supervised data-driven identification of neural markers of hand motor performance based on a supervised machine learning model. Data of 16 experimental sessions obtained from seven PD patients undergoing DBS therapy show that the supervised patient-specific neural markers provide improved decoding accuracy of hand motor performance, compared to group-level neural markers reported in the literature. We observed that the individual markers are sensitive to DBS therapy and thus, may represent controllable variables in an adaptive DBS system.15 p