scholarly journals Network controllability mediates the relationship between rigid structure and flexible dynamics

2021 ◽  
pp. 1-38
Author(s):  
Shi Gu ◽  
Panagiotis Fotiadis ◽  
Linden Parkes ◽  
Cedric H. Xia ◽  
Ruben C. Gur ◽  
...  
Keyword(s):  
Functional Connectivity ◽  
Network Architecture ◽  
Structural Connectivity ◽  
Network Control ◽  
Theoretical Frameworks ◽  
Wide Range ◽  
Complex Functions ◽  
Structural Network ◽  
Temporal Flexibility ◽  
The Relationship

Abstract Precisely how the anatomical structure of the brain supports a wide range of complex functions remains a question of marked importance in both basic and clinical neuroscience. Progress has been hampered by the lack of theoretical frameworks explaining how a structural network of relatively rigid inter-areal connections can produce a diverse repertoire of functional neural dynamics. Here, we address this gap by positing that the brain’s structural network architecture determines the set of accessible functional connectivity patterns according to predictions of network control theory. In a large developmental cohort of 823 youths aged 8 to 23 years, we found that the flexibility of a brain region’s functional connectivity was positively correlated with the proportion of its structural links extending to different cognitive systems. Notably, this relationship was mediated by nodes’ boundary controllability, suggesting that a region’s strategic location on the boundaries of modules may underpin the capacity to integrate information across different cognitive processes. Broadly, our study provides a mechanistic framework that illustrates how temporal flexibility observed in functional networks may be mediated by the controllability of the underlying structural connectivity.

scholarly journals Network controllability mediates the relationship between rigid structure and flexible dynamics

2021 ◽  
Author(s):  
Shi Gu ◽  
Panagiotis Fotiadis ◽  
Linden Parkes ◽  
Cedric H. Xia ◽  
Ruben C. Gur ◽  
...  
Keyword(s):  
Functional Connectivity ◽  
Control Theory ◽  
Network Architecture ◽  
Functional Module ◽  
Structural Connectivity ◽  
Cognitive Networks ◽  
Neural Dynamics ◽  
Boundary Controllability ◽  
Wide Range ◽  
Structural Network

ABSTRACTPrecisely how the anatomical structure of the brain supports a wide range of complex functions remains a question of marked importance in both basic and clinical neuroscience. Progress has been hampered by the lack of theoretical frameworks explaining how a structural network of relatively rigid inter-areal connections can produce a diverse repertoire of functional neural dynamics. Here, we address this gap by positing that the brain’s structural network architecture determines the set of accessible functional connectivity patterns according to predictions of network control theory. In a large developmental cohort of 823 youths aged 8 to 23 years, we found that the flexibility of a brain region’s functional connectivity was positively correlated with the proportion of its structural links extending to different cognitive systems. Notably, this relationship was mediated by nodes’ boundary controllability, suggesting that a region’s strategic location on the boundaries of modules may underpin the capacity to integrate information across different cognitive processes. Broadly, our study provides a mechanistic framework that illustrates how temporal flexibility observed in functional networks may be mediated by the controllability of the underlying structural connectivity.AUTHOR SUMMARYPrecisely how the relatively rigid white matter wiring of the human brain gives rise to a diverse repertoire of functional neural dynamics is not well understood. In this work, we combined tools from network science and control theory to address this question. Capitalizing on a large developmental cohort, we demonstrated that the ability of a brain region to flexibly change its functional module allegiance over time (i.e., its modular flexibility), was positively correlated with its proportion of anatomical edges projecting to multiple cognitive networks (i.e., its structural participation coefficient). Moreover, this relationship was strongly mediated by the region’s boundary controllability, a metric capturing its capacity to integrate information across multiple cognitive domains.

scholarly journals Two classes of functional connectivity in dynamical processes in networks

2021 ◽  
Vol 18 (183) ◽  
Author(s):  
Venetia Voutsa ◽  
Demian Battaglia ◽  
Louise J. Bracken ◽  
Andrea Brovelli ◽  
Julia Costescu ◽  
...  
Keyword(s):  
Functional Connectivity ◽  
Network Architecture ◽  
Structural Connectivity ◽  
Ecological Systems ◽  
Dynamical Processes ◽  
Structure And Dynamics ◽  
Theoretical View ◽  
And Function ◽  
The Relationship ◽  
Simultaneous Activity

The relationship between network structure and dynamics is one of the most extensively investigated problems in the theory of complex systems of recent 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, SC) with a (network) representation of the dynamics (functional connectivity, FC). 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, ecology, systems biology, neuroscience and socio-ecological systems. Seeing the organisation of 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.

scholarly journals Functional connectivity of fMRI using differential covariance predicts structural connectivity and behavioral reaction times

2021 ◽  
Author(s):  
Yusi Chen ◽  
Qasim Bukhari ◽  
Tiger Wutu Lin ◽  
Terrence J Sejnowski
Keyword(s):  
Magnetic Resonance Imaging ◽  
Magnetic Resonance ◽  
Functional Connectivity ◽  
Resting State ◽  
Structural Connectivity ◽  
Reaction Times ◽  
Resonance Imaging ◽  
Brain Areas ◽  
Human Connectome Project ◽  
Wide Range

Recordings from resting state functional magnetic resonance imaging (rs-fMRI) reflect the influence of pathways between brain areas. A wide range of methods have been proposed to measure this functional connectivity (FC), but the lack of ''ground truth'' has made it difficult to systematically validate them. Most measures of FC produce connectivity estimates that are symmetrical between brain areas. Differential covariance (dCov) is an algorithm for analyzing FC with directed graph edges. Applied to synthetic datasets, dCov-FC was more effective than covariance and partial correlation in reducing false positive connections and more accurately matching the underlying structural connectivity. When we applied dCov-FC to resting state fMRI recordings from the human connectome project (HCP) and anesthetized mice, dCov-FC accurately identified strong cortical connections from diffusion Magnetic Resonance Imaging (dMRI) in individual humans and viral tract tracing in mice. In addition, those HCP subjects whose rs-fMRI were more integrated, as assessed by a graph-theoretic measure, tended to have shorter reaction times in several behavioral tests. Thus, dCov-FC was able to identify anatomically verified connectivity that yielded measures of brain integration causally related to behavior.

Militarism, Capitalism, and the Nation-State: Towards a Realist Synthesis

1987 ◽  
Vol 5 (3) ◽  
pp. 283-302 ◽  
Author(s):  
J Lovering
Keyword(s):  
Industrial Complex ◽  
Science Literature ◽  
Theoretical Frameworks ◽  
Capitalist Production ◽  
State Institutions ◽  
Wide Range ◽  
Social And Economic Development ◽  
The Many ◽  
The Military ◽  
The Relationship

Military activities currently play a major role in social and economic development, even in noncombatant countries, This fact has received remarkably little attention in the social science literature, until recently. As a result, the theoretical frameworks which are available for the analysis of military activities arc underdeveloped. In this paper it is argued that there are in effect two such frameworks, derived from the Marxist and Weberian traditions, respectively. The many weaknesses of these, and the conflicts between them, are blurred rather than resolved in most recent studies of military phenomena, such as the ‘military industrial complex’. This is because the theory of the relationship between capitalist production and state institutions embedded in each perspective is seriously inadequate. A realist reconstruction is presented which highlights the significance of the national form of the state, and the contingent nature of capitalist production. This is designed to provide a new framework for appraising military activities, but it has implications for a wide range of questions concerned with the relationship between capital and state.

scholarly journals Unique mapping of structural and functional connectivity on cognition

2018 ◽  
Author(s):  
J. Zimmermann ◽  
J.G. Griffiths ◽  
A.R. McIntosh
Keyword(s):  
Functional Connectivity ◽  
Brain Connectivity ◽  
Structural Connectivity ◽  
Brain Regions ◽  
Unique Mapping ◽  
Human Connectome Project ◽  
Behavioural Patterns ◽  
Wide Range ◽  
Psychological Tasks ◽  
New Evidence

AbstractThe unique mapping of structural and functional brain connectivity (SC, FC) on cognition is currently not well understood. It is not clear whether cognition is mapped via a global connectome pattern or instead is underpinned by several sets of distributed connectivity patterns. Moreover, we also do not know whether the pattern of SC and of FC that underlie cognition are overlapping or distinct. Here, we study the relationship between SC and FC and an array of psychological tasks in 609 subjects from the Human Connectome Project (HCP). We identified several sets of connections that each uniquely map onto different aspects of cognitive function. We found a small number of distributed SC and a larger set of cortico-cortical and cortico-subcortical FC that express this association. Importantly, SC and FC each show unique and distinct patterns of variance across subjects and differential relationships to cognition. The results suggest that a complete understanding of connectome underpinnings of cognition calls for a combination of the two modalities.Significance StatementStructural connectivity (SC), the physical white-matter inter-regional pathways in the brain, and functional connectivity (FC), the temporal co-activations between activity of brain regions, have each been studied extensively. Little is known, however, about the distribution of variance in connections as they relate to cognition. Here, in a large sample of subjects (N = 609), we showed that two sets of brain-behavioural patterns capture the correlations between SC, and FC with a wide range of cognitive tasks, respectively. These brain-behavioural patterns reveal distinct sets of connections within the SC and the FC network and provide new evidence that SC and FC each provide unique information for cognition.

TASK GENERATION FOR DISTRIBUTED FUNCTIONAL MODEL

1996 ◽  
Vol 05 (03) ◽  
pp. 277-290
Author(s):  
TAKAFUMI SERA ◽  
AKIRA TAKURA
Keyword(s):  
Network Architecture ◽  
Functional Model ◽  
Network Control ◽  
Detailed Knowledge ◽  
Communication Service ◽  
Detailed Design ◽  
Internal Networks ◽  
Service State ◽  
Logical Functions ◽  
The Relationship

A new method is proposed to automatically generate the network control specifications necessary for executing services in a network from communications service specifications by using a knowledge of virtual resource that expresses logical functions in a network. Because these communication service specifications are described by observable terminal behaviors, the communication service specifications can be described without detailed knowledge of the network. The conventional stepwise description for network control specifications is manually performed for each network architecture. Then an expert, who has thorough knowledge of networks, must make a detailed design to comply with the requests of network architecture. Then an expert, who has thorough knowledge of internal networks, must make a detailed design to comply with the requests of network architecture. An expert can define in advance the relationship between a service state and a virtual resource and the relationship between a state transition of a virtual resource and task components and can store this knowledge in a database. Communications service specifications can be described without detailed knowledge of the network, and the network control specifications of the network can be derived from the communication service specifications.

scholarly journals Characterizing the role of the structural connectome in seizure dynamics

Brain ◽  
2019 ◽  
Vol 142 (7) ◽  
pp. 1955-1972 ◽  
Author(s):  
Preya Shah ◽  
Arian Ashourvan ◽  
Fadi Mikhail ◽  
Adam Pines ◽  
Lohith Kini ◽  
...  
Keyword(s):  
Functional Connectivity ◽  
Structure Function ◽  
Focal Epilepsy ◽  
Diffusion Imaging ◽  
Structural Connectivity ◽  
Patient Specific ◽  
High Angular Resolution ◽  
Intracranial Eeg ◽  
Structural Connectome ◽  
The Relationship

Abstract How does the human brain’s structural scaffold give rise to its intricate functional dynamics? This is a central question in translational neuroscience that is particularly relevant to epilepsy, a disorder affecting over 50 million subjects worldwide. Treatment for medication-resistant focal epilepsy is often structural—through surgery or laser ablation—but structural targets, particularly in patients without clear lesions, are largely based on functional mapping via intracranial EEG. Unfortunately, the relationship between structural and functional connectivity in the seizing brain is poorly understood. In this study, we quantify structure-function coupling, specifically between white matter connections and intracranial EEG, across pre-ictal and ictal periods in 45 seizures from nine patients with unilateral drug-resistant focal epilepsy. We use high angular resolution diffusion imaging (HARDI) tractography to construct structural connectivity networks and correlate these networks with time-varying broadband and frequency-specific functional networks derived from coregistered intracranial EEG. Across all frequency bands, we find significant increases in structure-function coupling from pre-ictal to ictal periods. We demonstrate that short-range structural connections are primarily responsible for this increase in coupling. Finally, we find that spatiotemporal patterns of structure-function coupling are highly stereotyped for each patient. These results suggest that seizures harness the underlying structural connectome as they propagate. Mapping the relationship between structural and functional connectivity in epilepsy may inform new therapies to halt seizure spread, and pave the way for targeted patient-specific interventions.

scholarly journals Dynamic reconfiguration of macaque brain networks during free-viewing of natural scenes

2021 ◽  
Author(s):  
Michael Ortiz-Rios ◽  
Fabien Belezeau ◽  
Marcus Haag ◽  
Michael C. Schmid ◽  
Marcus Kaiser
Keyword(s):  
Functional Connectivity ◽  
Functional Organization ◽  
Structural Connectivity ◽  
Centrality Measures ◽  
Contrast Imaging ◽  
Network Analyses ◽  
Free Viewing ◽  
Wide Range ◽  
Visual Scenes ◽  
Structural Networks

Natural vision involves the activation of a wide range of higher-level regions processing objects, motion, faces and actions. Here, we pursue a data-driven approach to explore how higher-level visual processes relate to the underlying structural and functional connectivity. Using a free-viewing paradigm in four awake rhesus macaque monkeys, we investigate how different visual scenes changes functional connectivity. Additionally, we explore how such functional connectivity, as measured through fMRI, is related to the structural connectivity, as measured through diffusion weighted imaging. At first, we evaluate the consistency of the elicited free-viewing pattern using standard analytical techniques. We also evaluate the underlying structural connectivity via diffusion data by tracking white matter bundle projections from visual cortex. We then reconstruct free-viewing and structural networks and quantify their properties. Centrality measures over the entire fMRI time-series revealed a consistent functional network engaged during free-viewing that included widespread hub regions across frontal (FEF, 46v), parietal (LIP, Tpt), and occipitotemporal cortex (MT, V4 and TE) among others. Interestingly, a small number of highly-weighted and long-length inter-hemispheric connections indicated the presence of long-range integrative properties during free-viewing. We hypothesized that during free-viewing, networks had the capacity to change their local and distal connections depending on the on-going changes in visual scenes. To capture these network dynamics, we departed from the static modular architecture of the structural networks and demonstrate that hubs in free-viewing networks reorganized according to the presence of objects, motion, and faces in the movie scenes indicating poly-functional properties. Lastly, we compare each NHP subject network and observed high consistency between individuals across same network type with closer correspondence between structural networks (e.g., diffusion based and tract-tracing networks). In summary, our network analyses revealed ongoing changes in large-scale functional organization present during free-viewing in the macaque monkey and highlight the advantages of multi-contrast imaging in awake monkeys for investigating dynamical processes in visual cognition. To further promote the use naturalistic free-viewing paradigms and increase the development of macaque neuroimaging resources, we share our datasets in the PRIME-DE consortium.

scholarly journals Cooperative Contributions of Structural and Functional Connectivity to Successful Memory and Aging

2017 ◽  
Author(s):  
Simon W Davis ◽  
Amanda Szymanski ◽  
Homa Boms ◽  
Thomas Fink ◽  
Roberto Cabeza
Keyword(s):  
Functional Connectivity ◽  
Associative Memory ◽  
Latent Variables ◽  
Memory Performance ◽  
Structural Connectivity ◽  
Equation Modeling ◽  
Cognitive Changes ◽  
Age Related ◽  
The Relationship ◽  
Age Related Changes

AbstractUnderstanding the precise relation between functional connectivity and structural (white-matter) connectivity and how these relationships account for cognitive changes in older adults are major challenges for neuroscience. We investigate these issues using a new approach in which structural equation modeling (SEM) is employed to integrate functional and structural connectivity data analyzed with a common framework based on regions connected by canonical tract groups (CTGs). CTGs (e.g., uncinate fasciculus, cingulum, etc.) serve as a common currency between functional and structural connectivity matrices, and ensures that the same amount of data contributing to brain-behavior relationships. We used this approach to investigate the neural mechanisms supporting memory for items and memory for associations, and how they are affected by healthy aging. Our results are threefold. Firstly, structural and functional CTGs made independent contributions to associative memory performance, suggesting that both forms of connectivity underlie age-related changes in associative memory. Secondly, distinct groups of CTGs supported associative versus item memory. Lastly, the relationship between functional and structural connectivity was best explained by the relationship between latent variables describing functional and structural CTGs based on a constrained set of tracts—but no one specific CTG group—suggesting that age effects in connectivity are constrained to specific pathways. These results provide further insights into the interplay between structural and functional connectivity patterns, and help to elucidate their relative contribution to age-related changes in associative memory performance.

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