Neuromodulation of Spatial Associations: Evidence from Choice Reaction Tasks During Transcranial Direct Current Stimulation

Various portions of human behavior and cognition are influenced by covert implicit processes without being necessarily available to intentional planning. Implicit cognitive biases can be measured in behavioral tasks yielding SNARC effects for spatial associations of numerical and non-numerical sequences, or yielding the implicit association test effect for associations between insect-flower and negative-positive categories. By using concurrent neuromodulation with transcranial direct current stimulation (tDCS), subthreshold activity patterns in prefrontal cortical regions can be experimentally manipulated to reduce implicit processing. Thus, the application of tDCS can test neurocognitive hypotheses on a unique neurocognitive origin of implicit cognitive biases in different spatial-numerical and non-numerical domains. However, the effects of tDCS are not only determined by superimposed electric fields, but also by task characteristics. To outline the possibilities of task-specific targeting of tDCS, task characteristics and instructions can be varied systematically when combined with neuromodulation. In the present thesis, implicit cognitive processes are assessed in different paradigms concurrent to left-hemispheric prefrontal tDCS to investigate a verbal processing hypothesis for implicit associations in general. In psychological experiments, simple choice reaction tasks measure implicit SNARC and SNARC-like effects as relative left-hand vs. right-hand latency advantages for responding to smaller number or ordinal sequence targets. However, different combinations of polarity-dependent tDCS with stimuli and task procedures also reveal domain-specific involvements and dissociations. Discounting previous unified theories on the SNARC effect, polarity-specific neuromodulation effects dissociate numbers and weekday or month ordinal sequences. By considering also previous results and patient studies, I present a hybrid and augmented working memory account and elaborate the linguistic markedness correspondence principle as one critical verbal mechanism among competing covert coding mechanisms. Finally, a general stimulation rationale based on verbal working memory is tested in separate experiments extending also to non-spatial implicit association test effects. Regarding cognitive tDCS effects, the present studies show polarity asymmetry and task-induced activity dependence of state-dependent neuromodulation. At large, distinct combinations of the identical tDCS electrode configuration with different tasks influences behavioral outcomes tremendously, which will allow for improved task- and domain-specific targeting

Modal logics are coalgebraic

Applications of modal logics are abundant in computer science, and a large number of structurally different modal logics have been successfully employed in a diverse spectrum of application contexts. Coalgebraic semantics, on the other hand, provides a uniform and encompassing view on the large variety of specific logics used in particular domains. The coalgebraic approach is generic and compositional: tools and techniques simultaneously apply to a large class of application areas and can moreover be combined in a modular way. In particular, this facilitates a pick-and-choose approach to domain specific formalisms, applicable across the entire scope of application areas, leading to generic software tools that are easier to design, to implement, and to maintain. This paper substantiates the authors' firm belief that the systematic exploitation of the coalgebraic nature of modal logic will not only have impact on the field of modal logic itself but also lead to significant progress in a number of areas within computer science, such as knowledge representation and concurrency/mobility

Intelligent Learning Rate Distribution to reduce Catastrophic Forgetting in Transformers

Pretraining language models on large text corpora is a common practice in natural language processing. Fine-tuning of these models is then performed to achieve the best results on a variety of tasks. In this paper, we investigate the problem of catastrophic forgetting in transformer neural networks and question the common practice of fine-tuning with a flat learning rate for the entire network in this context. We perform a hyperparameter optimization process to find learning rate distributions that are better than a flat learning rate. We combine the learning rate distributions thus found and show that they generalize to better performance with respect to the problem of catastrophic forgetting. We validate these learning rate distributions with a variety of NLP benchmarks from the GLUE dataset

Debiasing Sentence Embedders through Contrastive Word Pairs

Over the last years, various sentence embedders have been an integral part in the success of current machine learning approaches to Natural Language Processing (NLP). Unfortunately, multiple sources have shown that the bias, inherent in the datasets upon which these embedding methods are trained, is learned by them. A variety of different approaches to remove biases in embeddings exists in the literature. Most of these approaches are applicable to word embeddings and in fewer cases to sentence embeddings. It is problematic that most debiasing approaches are directly transferred from word embeddings, therefore these approaches fail to take into account the nonlinear nature of sentence embedders and the embeddings they produce. It has been shown in literature that bias information is still present if sentence embeddings are debiased using such methods. In this contribution, we explore an approach to remove linear and nonlinear bias information for NLP solutions, without impacting downstream performance. We compare our approach to common debiasing methods on classical bias metrics and on bias metrics which take nonlinear information into account

Langzeitergebnisse nach pulmonaler Thrombendarteriektomie (PTE)

Hintergrund der Studie: Die pulmonale Thrombendarteriektomie (PTE) ist die Therapie der Wahl der chronisch thromboembolisch pulmonalen Hypertonie (CTEPH). Es existieren nur wenige Daten bezüglich des Langzeitüberlebens, des Einflusses der residuell pulmonalen Hypertonie (res. pH) auf das Langzeitüberleben, der dazugehörigen Prädiktoren und einer Lernkurve des Operateurs. Das Ziel der vorliegenden Arbeit ist es, die genannten Daten zu erfassen und vergleichend auszuwerten. Methoden: Die vorliegende Studie umfasst 499 Patienten, bei denen zwischen Dezember 1995 und Dezember 2014 eine PTE an der Universitätsklinik des Saarlandes durchgeführt wurde. Die Daten wurden retrospektiv analysiert. Das Langzeitüberleben wurde mittels KaplanMeier-Kurven, die Prädiktoren mittels „Competing Risk Regression“ (CRR), COX- und linearen Regressionsmodellen ausgewertet. Die Untersuchung bezüglich einer Lernkurve des Operateurs wurde über drei chronologisch gebildete Subkohorten mit zweimal 166 und einmal 167 Patienten durchgeführt. Ergebnisse: Das Langzeitüberleben betrug nach 5, 10 und 15 Jahren 84,8 ± 1,9 %, 77,1 ± 2,7 % und 59,2 ± 5,3 %. 166 Patienten zeigten 48 h nach der PTE eine res. pH. Die Patienten, deren Todesursachen mit dem ätiologischen Formenkreis der CTEPH, oder der PTE direkt assoziiert waren, zeigten bei einem normalen pulmonalarteriellen Mitteldruck (PAPm) nach 10 Jahren eine Überlebensrate von 89,0 ± 2,7 %. Im Gegensatz dazu betrug die Überlebensrate bei Patienten mit res. pH 67,9 ± 4,7 %. Bezüglich des Langzeitüberlebens hatten Patienten mit einem New York Heart Association (NYHA) Stadium von 3 ein geringeres Risiko zu versterben, als die mit einem Stadium von 4 (sHR = 0,367, p = 0,0086). Ein höheres Kreatinin (sHR = 3,440, p < 0,0001) und ein niedrigeres Albumin (sHR = 0,907, p = 0,0274) zeigten neben einem hohen pulmonalvaskulären Widerstand (PVR) (sHR = 1,000, p = 0,0004), einem niedrigeren Herzzeitvolumen (HZV) (sHR = 0,530, p = 0,0041) und Herzindex (HI) (sHR = 0,300, p = 0,0052) ein ebenfalls geringeres Risiko. Eine längere kardiopulmonale Bypasszeit (CPB) (sHR = 1,020, p < 0,0001) und die Anzahl an desobliterierten Segmenten (sHR = 0,872, p = 0,0039) wurden neben dem postoperativen pulmonalarteriellen Mitteldruck (PAPm) (sHR = 1,140 & 1,100, p < 0,0001) und PVR (sHR = 1,010 & 1,000, p < 0,0001) ebenfalls als Prädiktoren identifiziert. Für die res. pH wurden die Anzahl an desobliterierten Segmenten (OR = 0,839, p = 0,0002), der postoperative PAPm (OR = 1,201 & 1,178, p < 0,0001) und PVR (OR = 1,006, p < 0,0001) als Prädiktoren detektiert. Bezüglich der Lernkurve des Operateurs zeigte sich über die drei Subkohorten eine signifikante (p < 0,0001) Verringerung der mittleren Zeiten des hypothermen Kreislaufstillstands (HCA) von 44,1 ± 21,2 min über 26,4 ± 10,5 min auf letztlich 23,7 ± 12,9 min. Die 30-Tages-Letalität verbesserte sich ebenfalls signifikant (p = 0,0007) von 13,3 % auf 9,0 % und letztlich 3,0 %. Schlussfolgerungen: Die prä- zu postoperativ verglichenen funktionell, invasiv und laborchemischen Werte und die Langzeitergebnisse bestätigen den Goldstandard der PTE in der Therapie der CTEPH. Mehrere Prädiktoren wurden identifiziert, welche Patienten detektieren können, die entweder sehr stark von einer PTE profitieren, oder postoperativ regelmäßig nachuntersucht werden sollten. Die über den Verlauf der drei Subkohorten abnehmenden HCA Zeiten und geringeren 30-Tages-Letalitäten bestätigen eine Lernkurve des Operateurs.Objective: Pulmonary endarterectomy (PEA) is the therapy of choice for chronic thromboembolic pulmonary hypertension (CTEPH). There are limited data regarding long-term survival, the effect of residual pulmonary hypertension (res. pH) on long-term survival, their predictors and a learning curve of the surgeon. The aim of this study is to collect and compare these data. Methods: Between December 1995 and December 2014, 499 patients underwent PEA at the Saarland University Medical Center. The data were analyzed retrospectively. Long-term survival was analyzed using Kaplan-Meier curves and predictors using competing risk regression, COXand linear regression models. To examine a learning curve of the surgeon three subcohorts were grouped chronologically, which included twice 166 and once 167 patients. Results: Overall survival rates at 5, 10 and 15 years after the surgery were 84.8 ± 1.9 %, 77.1 ± 2.7 % and 59.2 ± 5.3 %. 166 patients had res. pH 48 h after PEA. If the cause of death was etiologically related to CTEPH, or directly associated to PEA, patients survival rates at 10 years were 89.0 ± 2.7 %. In contrast, survival rates of patients with a res. pH were 67.9 ± 4.7 %. Patients with a New York Heart Association (NYHA) functional class of 3 had a lower risk of dying in long-term than those with a functional class of 4 (sHR = 0.367, p = 0.0086). A higher creatinine (sHR = 3.440, p < 0.0001) and a lower albumin (sHR = 0.907, p = 0.0274) showed a lower risk, in addition to a high pulmonary vascular resistance (PVR) (sHR = 1.000, p = 0.0004), a lower cardiac output (CO) (sHR = 0.530, p = 0.0041) and cardiac index (CI) (sHR = 0.300, p = 0.0052). Longer cardiopulmonary bypass time (CPB) (sHR = 1.020, p < 0.0001) and the number of desobliterated segments (sHR = 0.872, p = 0.0039) were also identified as predictors along with postoperative mean pulmonary pressure (PAPm) (sHR = 1.140 & 1.100, p < 0.0001) and PVR (sHR = 1.010 & 1.000, p < 0.0001). The number of desobliterated segments (OR = 0.839, p = 0.0002), the postoperative PAPm (OR = 1.201 & 1.178, p < 0.0001) and PVR (OR = 1.006, p < 0.0001) were detected as predictors for the res. pH. Regarding the learning curve a reduction of the mean time of hypothermic cardiac arrest (HCA) was observed over the three subcohorts, from 44.1 ± 21.2 min over 26.4 ± 10.5 min to finally 23.7 ± 12.9 min. The 30-day mortality rate also improved significantly (p = 0.0007) from 13.3 % to 9.0 % and finally 3.0 %. Conclusions: The functional, invasive and laboratory chemistry values compared preoperatively and postoperatively and the long-term results confirm the gold standard of PTE in CTEPH therapy. Several predictors have been identified which can detect patients who either benefit greatly from PTE, or who should be regularly examined postoperatively. The decreasing HCA times over the course of the three subcohorts and also the lower 30-day mortality rates confirm a learning curve of the surgeon