167 research outputs found
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 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
Connectivity between mPFC and PCC predicts postâchoice attitude change: The selfâreferential processing hypothesis of choice justification
Prior research shows that after making a choice, decision makers shift their attitudes in a choiceâcongruous direction. Although this postâchoice 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 selfâknowledge to justify the choice they have made. This selfâreferential processing of the choice is thought to play a pivotal role in the postâchoice attitude change. Twentyâfour 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 selfâregions (medial prefrontal cortex and posterior cingulate cortex/precuneus]) during the postâchoice (vs. preâchoice) rating of the chosen options predicted the postâchoice shift of the attitudes toward the chosen options. This finding is the first to suggest that cognitive integration of various selfârelevant cognitions is instrumental in fostering postâchoice attitude change. Hum Brain Mapp 37:3810â3820, 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
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
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 lÀrande ihop? En studie om pedagogers resonemang och arbete kring det informella lek- lÀrandet i förskoleklassen
Syfte:
VÄrt syfte har varit att undersöka hur resonerar pedagoger kring det informella lek- lÀrandet och hur de arbetar
med detta i förskoleklassen.
FrÄgestÀllningar:
-Vilka lekinslag förekommer i den planerade verksamheten/undervisningen?
-Vem samspelar med vem?
-Förkommer parallella lekaktiviteter i undervisningen?
-Vilka planerade informella lÀrandesituationer förkommer?
Metod:
Studien har prÀglats av en kvalitativ undersökningsmetod dÀr vi har anvÀnt oss av löpande observationer och
semistrukturerade intervjuer. Studien har utförts i tvÄ Älderhomogena förskoleklasser och har koncentrerats till
tre olika observationsepisoder. Vi har ocksÄ kompletterat observationerna genom intervjuer med respektive lÀ-
rare för förskoleklasserna. Vid observationerna anvÀndes observationsmall och vid intervjutillfÀllena anvÀndes
bandspelare (diktafon).
Resultat:
I vÄr studie har vi mÀrkt hur pedagogernas instÀllning till lÀrande har en avgörande roll för hur verksamheten
utformas. UtifrÄn vÄrt resultat har vi kunnat se att pedagoger som anser att lek och lÀrande hör ihop ocksÄ försö-
ker att införa denna form av lÀrande i sin undervisning det vill sÀga informellt lek- lÀrande. De lekinslag och
planerade informella lÀrandesituationer som har förkommit under observationerna har bland annat innehÄllit
klosslek, sÄng och ramslek. Vi har Àven tagit del av en samlings aktivitet dÀr barnens tidigare erfarenheter kring
deras nÀrmiljö har diskuterats och varit i fokus. Vi har funnit att parallella aktiviteter i undervisningen har för-
kommit men dock i mindre utstrÀckning. I vÄr studie har samspelet mellan lÀrare  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 VerknĂŒpfung von selbstreferenzieller Verarbeitung (SRV)
und episodischem GedÀchtnisabruf (EGA) sowie deren gemeinsame und exklusive
neuronale ReprĂ€sentation untersucht. Standardexperimentalaufgaben fĂŒr 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, fĂŒhrten zu Anstiegen in den
Blutsauerstoffgehalt-abhÀngigen (BOLD) Signalen (im Folgenden als
âAktivierungenâ bezeichnet) insbesondere im posterioren Cingulum (PCC), dem
anterioren Praecuneus, dem medialen prÀfrontalen Cortex (MPFC) und inferioren
Anteilen des Lobulus parietalis inferior. Im Gegensatz dazu waren bei der EGA
Aktivierungen im posterioren Praecuneus, dem anterioren prÀfrontalen Cortex
(aPFC), sowie superioren Anteilen des Lobulus parietalis inferior nachweisbar.
Gemeinsame Aktivierungen von SRV und EGA fanden sich zwischen den zuvor
erwÀhnten Regionen im Praecuneus und im inferioren Parietallappen, nicht
jedoch im prÀfrontalen 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
gegenĂŒber 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 IntensitÀt
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
âYoung-Mania-Rating-Scaleâ (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 FĂ€higkeit zur emotionalen Modulation angenommen wird. In einem
fMRT-Experiment wurden Patienten und gesunden Kontrollpersonen emotionale
Bilder mit und ohne Erwartungshinweis gezeigt. WĂ€hrend 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 verÀnderte prÀfrontale Modulation könnte bei der
Depression zur klinisch beobachtbaren verminderten emotionalen
ModulationsfÀhigkeit 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 fĂŒr 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
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