The Role of the Nucleus Accumbens and Rostral Anterior Cingulate Cortex in Anhedonia: Integration of Resting EEG, fMRI, and Volumetric Techniques

Anhedonia, the reduced propensity to experience pleasure, is a promising endo-- phenotype and vulnerability factor for several psychiatric disorders, including depression and schizophrenia. In the present study, we used resting electroencephalography, functional magnetic resonance imaging, and volumetric analyses to probe putative associations between anhedonia and individual differences in key nodes of the brain's reward system in a non-clinical sample. We found that anhedonia, but not other symptoms of depression or anxiety, was correlated with reduced nucleus accumbens (NAcc) responses to rewards (gains in a monetary incentive delay task), reduced NAcc volume, and increased resting delta current density (i.e., decreased resting activity) in the rostral anterior cingulate cortex (rACC), an area previously implicated in positive subjective experience. In addition, NAcc reward responses were inversely associated with rACC resting delta activity, supporting the hypothesis that delta might be lawfully related to activity within the brain's reward circuit. Taken together, these results help elucidate the neural basis of anhedonia and strengthen the argument for anhedonia as an endophenotype for depression.Psycholog

Understanding the Formation of Trust in IT Artifacts

IT artifacts often take the role of a trustee in a trust relationship between users and IT artifacts. The goal of this paper is to increase the understanding of the formation of trust in such trust relationships. Instead of using the predominant theoretical foundation of interpersonal trust, we use the theoretical foundation of trust in automation from the HCI discipline for studying the formation of trust. Since we aim at creating insights on the formation of trust and its dimensions, we develop a formative first-order, formative second-order measurement model for trust. To evaluate the impact of the single indicators and dimensions on trust, we conduct a laboratory experiment. Our results show that the dimensions performance, process and purpose have a comparable impact on trust, and that indicators related to user data are especially important. The results complement existing insights, deepening the understanding of the formation of trust in IT artifacts

A non-standard finite-difference-method for a non-autonomous epidemiological model: analysis, parameter identification and applications

In this work, we propose a new non-standard finite-difference-method for the numerical solution of the time-continuous non-autonomous susceptible-infected-recovered model. For our time-discrete numerical solution algorithm, we prove preservation of non-negativity and show that the unique time-discrete solution converges linearly towards the time-continuous unique solution. In addition to that, we introduce a parameter identification algorithm for the susceptible-infected-recovered model. Finally, we provide two numerical examples to stress our theoretical findings

Acute tryptophan depletion attenuates brain-heart coupling following external feedback

External and internal performance feedback triggers neural and visceral modulations such as reactions in the medial prefrontal cortex and insulae or changes of heart period (HP). The functional coupling of neural and cardiac responses following feedback (cortico-cardiac connectivity) is not well understood. While linear time-lagged within-subjects correlations of single-trial EEG and HP (cardio-electroencephalographic covariance tracing, CECT) indicate a robust negative coupling of EEG magnitude 300 ms after presentation of an external feedback stimulus with subsequent alterations of heart period (the so-called N300H phenomenon), the neurotransmitter systems underlying feedback-evoked cortico-cardiac connectivity are largely unknown. Because it has been shown that acute tryptophan depletion (ATD), attenuating brain serotonin (5-HT), decreases cardiac but not neural correlates of feedback processing, we hypothesized that 5-HT may be involved in feedback-evoked cortico-cardiac connectivity. In a placebo-controlled double-blind cross-over design, 12 healthy male participants received a tryptophan-free amino-acid drink at one session (TRP−) and a balanced amino-acid control-drink (TRP+) on another and twice performed a time-estimation task with feedback presented after each trial. N300H magnitude and plasma tryptophan levels were assessed. Results indicated a robust N300H after TRP+, which was significantly attenuated following TRP−. Moreover, plasma tryptophan levels during TRP+ were correlated with N300H amplitude such that individuals with lower tryptophan levels showed reduced N300H. Together, these findings indicate that 5-HT is important for feedback-induced covariation of cortical and cardiac activity. Because individual differences in anxiety have previously been linked to 5-HT, cortico-cardiac coupling and feedback processing, the present findings may be particularly relevant for futures studies on the relationship between 5-HT and anxiety

Evidence of a dynamic ice sheet system in Filchner Trough until the early Holocene

The past ice sheet conditions in the southern Weddell Sea Embayment (WSE) are only poorly known. Studies from this area have led to two contradicting scenarios of maximum ice extent during the Last Glacial Maximum (LGM). The first scenario is mainly based on terrestrial data indicating only very limited ice sheet thickening in the hinterland and suggests a grounding-line position on the inner shelf. The alternative scenario is based on marine geological and geophysical data and concludes that the LGM grounding line was located on the outer shelf, about 650 km further offshore than in the other scenario. Three hypotheses have been brought forward to explain these two apparently contradictory scenarios. A) An ice plain was present on the shelf that enabled a large ice extent while maintaining little ice thickness in the hinterland. B) The maximum grounded ice advance lasted for a short period only and was probably caused by a short-termed touch down of an ice shelf on the outer shelf, which did not cause sufficient ice sheet thickening in the hinterland to be traced today. C) Due to an ice flow switch, Filchner Trough was fed by an area further to the west where ice had thickened at the LGM. Besides the poorly constrained LGM ice extent, studies suggest a complex development of its retreat speed and drainage pattern in succession of the LGM that needs to be further constraint. For example, radar data from ice rises in the southwestern hinterland of the WSE suggest that ice flow switches occurred as late as the Mid-Holocene and cosmogenic exposure ages indicate an early Holocene ice sheet thickness in the Ellsworth Mountains comparable to that of the LGM. We investigated multibeam bathymetry data (ATLAS Hydrosweep DS3), acoustic sub-bottom profiles (ATLAS Parasound P-70) and marine sediment cores collected from Filchner Trough during RV “Polarstern” expedition PS96 in Dec 2015-Feb 2016. Our key finding is a previously unknown stacked grounding zone wedge (GZW) located on the outer shelf. This GZW shows that the Filchner palaeo-ice stream stabilized at this position at least two times. Two sediment cores were recovered seaward of the GZW and on top of the lower part of the GZW, respectively. Radiocarbon dates from these cores indicate that (i) the GZW was formed in the Early Holocene and (ii) grounded ice did not extend seaward of the GZW at the LGM. Hence, our data provide evidence that the grounding line in Filchner Trough experienced dynamic changes in the Holocene and that no linear ice sheet retreat occurred within this trough after the LGM