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10. A stylised view on structural and functional connectivity in dynamical processes in networks

Author

Voutsa, Venetia, Battaglia, Demian, Bracken, Louise J., Brovelli, Andrea, Costescu, Julia, Munoz, Mario Diaz, Fath, Brian D., Funk, Andrea, Guirro, Mel, Hein, Thomas, Kerschner, Christian, Kimmich, Christian, Lima, Vinicius, Messe, Arnaud, Parsons, Anthony J., Perez, John, Pöppl, Ronald, Prell, Christina, Recinos, Sonia, Shi, Yanhua, Tiwari, Shubham, Turnbull, Laura, Wainwright, John, Waxenecker, Harald, and Hütt, Marc-Thorsten

Subjects
Physics - Physics and Society, Quantitative Biology - Molecular Networks, Quantitative Biology - Neurons and Cognition
Abstract

The relationship of network structure and dynamics is one of most extensively investigated problems in the theory of complex systems of the last years. Understanding this relationship is of relevance to a range of disciplines -- from Neuroscience to Geomorphology. A major strategy of investigating this relationship is the quantitative comparison of a representation of network architecture (structural connectivity) with a (network) representation of the dynamics (functional connectivity). Analysing such SC/FC relationships has over the past years contributed substantially to our understanding of the functional role of network properties, such as modularity, hierarchical organization, hubs and cycles. Here, we show that one can distinguish two classes of functional connectivity -- one based on simultaneous activity (co-activity) of nodes the other based on sequential activity of nodes. We delineate these two classes in different categories of dynamical processes -- excitations, regular and chaotic oscillators -- and provide examples for SC/FC correlations of both classes in each of these models. We expand the theoretical view of the SC/FC relationships, with conceptual instances of the SC and the two classes of FC for various application scenarios in Geomorphology, Freshwater Ecology, Systems Biology, Neuroscience and Social-Ecological Systems. Seeing the organization of a dynamical processes in a network either as governed by co-activity or by sequential activity allows us to bring some order in the myriad of observations relating structure and function of complex networks.

Published
2021

12. Anxiety and computations of uncertainty during reward-based learning in volatile environments

Author

Hein, Thomas

Abstract

Uncertainty plays a core mechanistic role in computational psychiatric accounts of clinical disorders. This thesis tests the hypothesis that subclinical anxiety interferes with uncertainty processing and reward learning in unstable environments. In a series of four experiments using a combination of computational modelling and reward-based learning tasks with electrophysiological and neuromagnetic data, we detail the relationships between anxiety, decision making, and uncertainty (inverse, precision) estimates. Using EEG and a hierarchical Bayesian filtering model of behaviour, the first experiment shows how experiencing a temporary state of anxiety can bias uncertainty estimates essential for optimal belief updates in Bayesian theories of learning and impede overall reward learning performance. We also tracked the expression of belief update signals in trial-by-trial EEG amplitudes, revealing precision-weighted prediction errors (pwPE) about stimulus outcomes were represented in the control group only. In the second study, we investigated how the behavioural and modelling findings from the first experiment are associated with the oscillatory representations of pwPEs and predictions hypothesised in predictive coding and Bayesian inference frameworks. Using convolution modelling for EEG oscillatory responses, we reveal the influence of biased uncertainty estimates in state anxiety on the oscillations encoding predictions and pwPEs during reward learning. For the third study, we asked how motivation to reduce anxiety may improve reward-based learning, detailing null results due to unsuccessfully inducing a state of anxiety. Using MEG, the final experimental chapter examined the effects of high levels of trait anxiety on reward learning and the spectral signatures of predictions and pwPEs. We show how high trait anxiety amplifies volatility estimates and increases uncertainty, impairing reward learning and altering the oscillatory responses encoding pwPEs. Together, the results from this thesis suggest that subclinical anxiety impedes reward-based learning by biasing uncertainty estimates and altering the neural encoding of pwPEs and predictions considered essential for optimal belief updating.

Published
2021
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32. Baseflow and Coupled Nitrification-Denitrification Processes Jointly Dominate Nitrate Dynamics in a Watershed Impacted by Rare Earth Mining

Author

Shu, Wang, Zhang, Qiuying, Audet, Joachim, Hein, Thomas, Leng, Peifang, Hu, Mei, Li, Zhao, Cheng, Hefa, Chen, Gang, Li, Fadong, and Wu, Fengchang

Abstract

Mining activities cause severe nitrogen pollution in watersheds, yet our understanding of the transport pathways, transformation processes, and control mechanisms of nitrate (NO3–) in these areas is limited. Based on nearly 4-year observations of groundwater and river in China’s largest ion-adsorption rare earth mining watershed, we revealed the dynamics of NO3–and its drivers using stoichiometry-based load model, molecular biological, and multi-isotope approaches. Results indicated that the NO3–dynamics were jointly controlled by sources (precipitation, terrestrial inputs, and sediment supply) and processes (hydrological and biological). The monthly NO3–export load from the 444.4 km2watershed was 3.72 × 105kg. Groundwater (36 ± 26%) and soil nitrogen (25 ± 17%) were the primary exogenous sources of NO3–. Baseflow was the main hydrological pathway for legacy nitrogen into the river, contributing 66.8% of the NO3–load. Coupled nitrification-denitrification were key biological processes affecting the NO3–transformation, with denitrification contributing 58%. Burkholderiawere most associated with NO3–transformation. Dissolved organic carbon and oxygen were major drivers affecting the NO3–production and consumption. This study highlights effective control and management strategies for nitrogen pollution in mining-affected watersheds, considering not only reducing nitrogen inputs but also integrating hydrological pathways and nitrogen transformation mechanisms.

Published
2025
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37. The Danube River Basin

Author

Sommerwerk, Nike, primary, Bloesch, Jürg, additional, Baumgartner, Christian, additional, Bittl, Thomas, additional, Čerba, Dubravka, additional, Csányi, Béla, additional, Davideanu, Grigore, additional, Dokulil, Martin, additional, Frank, Georg, additional, Grecu, Iulia, additional, Hein, Thomas, additional, Kováč, Vladimír, additional, Nichersu, Iulian, additional, Mikuska, Tibor, additional, Pall, Karin, additional, Paunović, Momir, additional, Postolache, Carmen, additional, Raković, Maja, additional, Sandu, Cristina, additional, Schneider-Jacoby, Martin, additional, Stefke, Katharina, additional, Tockner, Klement, additional, Toderaş, Ion, additional, and Ungureanu, Laurenţia, additional

Published
2022
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39. Research on coupled socio‐ecohydrological systems—implementing a highly integrative and interdisciplinary research agenda in the Doctoral School "Human River Systems in the 21st Century (HR21)".

Author

Hein, Thomas, Auhser, Alexander, Byekwaso, Flavia, Graf, Wolfram, Hoevel, Adriane, Schmid, Martin, Stockinger, Michael, Stumpp, Christine, Tschikof, Martin, Tuerk, Hatice, and Weigelhofer, Gabriele

Subjects
WATER management, WATERSHEDS, NATURAL resources, MOUNTAIN ecology, WATER supply, WETLANDS
Abstract

The access to an adequate quantity and quality of water is vital to sustain healthy ecosystems and human socioeconomic development. However, the shift from an agrarian, solar energy based to an industrialized, fossil fuel‐based socio‐metabolic regime has put natural water resources under stress and led to dramatic transformations of riverine landscapes in the Anthropocene. Thus, we need interdisciplinary research approaches that integrate the knowledge and methods from ecology, humanities, and engineering. The Doctoral School "Human River Systems in the 21st Century" (HR21) studies riverine landscapes as coupled socio‐ecohydrological systems (SEHS) within four research clusters, that is, connectivity, metabolism, vulnerability, and governance. HR21 analyzes the transformation processes and coevolution of nature and society in rivers and their response to future environmental, social, cultural, and economic drivers of change. HR21 aims to improve the understanding of the coupling of the socioeconomic, ecological, and hydrological systems within industrialized riverine landscapes to support their urgent, more sustainable transformation. To discuss how this agenda can be implemented, five different HR21 PhD projects are presented, clearly routed in one scientific domain, applying a combination of the research clusters and addressing various topics: (i) hydropower effects in high alpine river ecosystems, (ii) wastewater impacts on carbon storage and greenhouse gas fluxes in tropical wetlands, (iii) the nutrient retention and ecosystem service potential of floodplains in large river catchments, and the influence of hydrometeorological variables on (iv) the runoff response and on (v) the transit time distribution of runoff, both impacting water resource management at the basin level. These examples highlight how disciplinary PhD research can be framed within an interdisciplinary research agenda to coupled SEHS. [ABSTRACT FROM AUTHOR]

Published
2024
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40. Water‐controlled ecosystems as complex networks: Evaluation of network‐based approaches to quantify patterns of connectivity.

Author

Tiwari, Shubham, Brizuela, Sonia Recinos, Hein, Thomas, Turnbull, Laura, Wainwright, John, and Funk, Andrea

Subjects
LANDSCAPE ecology, FUNCTIONAL connectivity, ENVIRONMENTAL protection, ENVIRONMENTAL management, HYDROLOGY, GEOMORPHOLOGY
Abstract

This study provides a new perspective on understanding the intricacies of water‐mediated connectivity in ecosystems, bridging landscape ecology and geomorphology through network science. We highlight dryland and river‐floodplain ecosystems as distinct examples of contrasting water‐controlled systems. We (1) discuss central considerations in developing structural connectivity and functional connectivity networks of water‐mediated connectivity; (2) quantify the emergent patterns in these networks; and (3) evaluate the capacity of network science tools for investigating connectivity characteristics. With a focus on strength (weights) and direction, connectivity is quantified using seven parameters at both network and node levels. We find that link density, betweenness centrality and page rank centrality are highly sensitive to directionality; global efficiency and degree centrality are particularly sensitive to weights; and relative node efficiency remains unaffected by weights and directions. Our study underscores how network science approaches can transform how we quantify and understand water‐mediated connectivity, especially in consideration of the role(s) of weights and directionality. This interdisciplinary perspective, linking ecology, hydrology and geomorphology, has implications for both theoretical insights and practical applications in environmental management and conservation efforts. [ABSTRACT FROM AUTHOR]

Published
2024
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48. Reviving Europe's rivers: Seven challenges in the implementation of the Nature Restoration Law to restore free-flowing rivers

Author

Stoffers, Twan, Altermatt, Florian, Baldan, Damiano, Bilous, Olena, Borgwardt, Florian, Buijse, Anthonie D., Bondar-Kunze, Elisabeth, Cid, Nuria, Erős, Tibor, Ferreira, Maria Teresa, Funk, Andrea, Haidvogl, Gertrud, Hohensinner, Severin, Kowal, Johannes, Nagelkerke, Leopold A.J., Neuburg, Jakob, Peller, Tianna, Schmutz, Stefan, Singer, Gabriel A., Unfer, Günther, Vitecek, Simon, Jähnig, Sonja C., Hein, Thomas, Stoffers, Twan, Altermatt, Florian, Baldan, Damiano, Bilous, Olena, Borgwardt, Florian, Buijse, Anthonie D., Bondar-Kunze, Elisabeth, Cid, Nuria, Erős, Tibor, Ferreira, Maria Teresa, Funk, Andrea, Haidvogl, Gertrud, Hohensinner, Severin, Kowal, Johannes, Nagelkerke, Leopold A.J., Neuburg, Jakob, Peller, Tianna, Schmutz, Stefan, Singer, Gabriel A., Unfer, Günther, Vitecek, Simon, Jähnig, Sonja C., and Hein, Thomas

Abstract

The EU Nature Restoration Law represents an important opportunity for freshwater habitat restoration and, consequently, freshwater biodiversity protection. However, a number of challenges must be anticipated in its implementation, which may compromise its success. Some aspects, particularly those relating to freshwater ecosystems, require more clarification. We use riverine ecosystems to illustrate existing ambiguities in the proposed legislation and the potential consequences of leaving these aspects open to interpretation during the implementation process. We also discuss potential solutions to these problems which could help ensure that the law's objectives are met. We argue that river network structure and connectivity dimensions, which result into river meta-ecosystems, must be explicitly considered. For that purpose, we ask for clear definitions of the critical terms “free-flowing rivers,” “barriers,” and “reference areas.” In addition, we recommend developing methods for integrated assessment of connectivity across river networks. As a key property of river ecosystems, this must be used to prioritize actions to increase the length and number of free-flowing rivers. Adequate restoration planning at larger spatial scales will benefit from a meta-ecosystem perspective and accurate representation of aquatic-terrestrial linkages, which will significantly improve the efficacy of restoration efforts. Furthermore, stakeholder and citizen engagement offer important opportunities at local, national, and European scales, and should be fostered to ensure inclusive decision-making. The conservation challenges outlined here are particularly important for rivers, but they also have implications for other ecosystems. These considerations are useful for policymakers, conservationists, and other stakeholders involved in the Nature Restoration Law and related policy initiatives. This article is categorized under: Water and Life > Stresses and Pressures on Ecosystems Water and L

Published
2024

49. ASMR amplifies low frequency and reduces high frequency oscillations

Author

Swart, Thomas R., Banissy, Michael J., Hein, Thomas P., Bruña Fernández, Ricardo, Pereda, Ernesto, Bhattacharya, Joydeep, Swart, Thomas R., Banissy, Michael J., Hein, Thomas P., Bruña Fernández, Ricardo, Pereda, Ernesto, and Bhattacharya, Joydeep

Abstract

Autonomous sensory meridian response (ASMR) describes an atypical multisensory experience of calming, tingling sensations in response to a specific subset of social audiovisual triggers. To date, the electrophysiological (EEG) correlates of ASMR remain largely unexplored. Here we sought to provide source-level signatures of oscillatory changes induced by this phenomenon and investigate potential decay effects-oscillatory changes in the absence of self-reported ASMR. We recorded brain activity using EEG as participants watched ASMR-inducing videos and self-reported changes in their state: no change (Baseline); enhanced relaxation (Relaxed); and ASMR sensations (ASMR). Statistical tests in the sensor-space were used to inform contrasts in the source-space, executed with beamformer reconstruction. ASMR modulated oscillatory power by decreasing high gamma (52-80 Hz) relative to Relaxed and by increasing alpha (8-13 Hz) and decreasing delta (1-4 Hz) relative to Baseline. At the source level, ASMR increased power in the low-mid frequency ranges (8-18 Hz) and decreased power in high frequency (21-80 Hz). ASMR decay effects reduced gamma (30-80 Hz) and in the source-space reduced high-beta/gamma power (21-80 Hz). The temporal profile of ASMR modulations in high-frequency power later shifts to lower frequencies (1-8 Hz), except for an enhanced alpha, which persists for up to 45 min post self-reported ASMR. Crucially, these results provide the first evidence that the cortical sources of ASMR tingling sensations may arise from decreases in higher frequency oscillations and that ASMR may induce a sustained relaxation state., BIAL Foundation, Depto. de Radiología, Rehabilitación y Fisioterapia, Fac. de Medicina, TRUE, pub

Published
2024

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