Optimality of Human Contour Integration

For processing and segmenting visual scenes, the brain is required to combine a multitude of features and sensory channels. It is neither known if these complex tasks involve optimal integration of information, nor according to which objectives computations might be performed. Here, we investigate if optimal inference can explain contour integration in human subjects. We performed experiments where observers detected contours of curvilinearly aligned edge configurations embedded into randomly oriented distractors. The key feature of our framework is to use a generative process for creating the contours, for which it is possible to derive a class of ideal detection models. This allowed us to compare human detection for contours with different statistical properties to the corresponding ideal detection models for the same stimuli. We then subjected the detection models to realistic constraints and required them to reproduce human decisions for every stimulus as well as possible. By independently varying the four model parameters, we identify a single detection model which quantitatively captures all correlations of human decision behaviour for more than 2000 stimuli from 42 contour ensembles with greatly varying statistical properties. This model reveals specific interactions between edges closely matching independent findings from physiology and psychophysics. These interactions imply a statistics of contours for which edge stimuli are indeed optimally integrated by the visual system, with the objective of inferring the presence of contours in cluttered scenes. The recurrent algorithm of our model makes testable predictions about the temporal dynamics of neuronal populations engaged in contour integration, and it suggests a strong directionality of the underlying functional anatomy

Modelling human choices: MADeM and decision‑making

Research supported by FAPESP 2015/50122-0 and DFG-GRTK 1740/2. RP and AR are also part of the Research, Innovation and Dissemination Center for Neuromathematics FAPESP grant (2013/07699-0). RP is supported by a FAPESP scholarship (2013/25667-8). ACR is partially supported by a CNPq fellowship (grant 306251/2014-0)

Culture beats gender? The importance of controlling for identity- and parenting-related risk factors in adolescent psychopathology

This study analyzed the unique effects of gender and culture on psychopathology in adolescents from seven countries after controlling for factors which might have contributed to variations in psychopathology. In a sample 2259 adolescents (M = 15 years; 54% female) from France, Germany, Turkey, Greece, Peru, Pakistan, and Poland identity stress, coping with identity stress, maternal parenting (support, psychological control, anxious rearing) and psychopathology (internalizing, externalizing and total symptomatology) were assessed. Due to variations in stress perception, coping style and maternal behavior, these covariates were partialed out before the psychopathology scores were subjected to analyses of variance with gender and country as factors. These analyses leveled out the main effect of country and revealed country-specific gender effects. In four countries, males reported higher internalizing and total symptomatology than females. Partialing out the covariates resulted in a clearer picture of culture-specific and gender-dependent effects on psychopathology, which is helpful in designing interventions. © 2017 The Foundation for Professionals in Services for Adolescent

Quantification of Antibiotic in Biofilm-Inhibiting Multilayers by 7.87 eV Laser Desorption Postionization MS Imaging

The potential of laser desorption postionization mass spectrometry (LDPI-MS) imaging for small molecule quantification is demonstrated here. The N-methylpiperazine acetamide of (MPA) ampicillin was adsorbed into polyelectrolyte multilayer surface coatings composed of chitosan and alginate, both high molecular weight biopolymers. These MPA-ampicillin spiked multilayers were then shown to inhibit the growth of E. faecalis biofilms that play a role in early stage infection of implanted medical devices. Finally, LDPI-MS imaging using 7.87 eV single photon ionization was found to detect MPA-ampicillin with the multilayers before and after biofilm growth with limits of quantification and detection of 0.6 and 0.3 nmoles, respectively. The capabilities of LDPI-MS imaging for small molecule quantification are compared to those of MALDI-MS. Furthermore, these results indicate that 7.87 eV LDPI-MS imaging should be applicable to quantification of a range of small molecular species on a variety of complex organic and biological surfaces. Finally, while MS imaging for quantification was demonstrated here using LDPI, it is a generally useful strategy that can be applied to other methods