scholarly journals How Top-Down and Bottom-Up Regulation in Fronto-Amygdalar Network Changes over Time during Drug Cue-Exposure: An fMRI Study among Abstinent Heroin User

2019 ◽  
Author(s):  
Arash Zare-Sadeghi ◽  
Mohammad Ali Oghabian ◽  
Mehran Zare-Bidoky ◽  
Seyed Amir Hossein Batouli ◽  
Hamed Ekhtiari
Keyword(s):  
Regulatory Networks ◽  
Cue Reactivity ◽  
Network Connectivity ◽  
Heroin User ◽  
Top Down ◽  
Cue Exposure ◽  
Down Regulation ◽  
Potential Biomarker ◽  
Over Time ◽  
Drug Cue

AbstractTop-down regulation is one of the major neural cores in drug-craving management and relapse prevention. The dynamic temporal behavior of top-down regulation between the dorso-lateral and ventro-medial prefrontal cortices (DLPFC and VMPFC) and amygdala during drug cue-exposure has not been studied yet. Fifteen abstinent participants with heroin use disorder were scanned using drug cue-induced craving fMRI task. Using Dynamic Causal Modelling (DCM), the winning model showed a significant reciprocal connection between the VMPFC and DLPFC while there was a one-way effect of the VMPFC on the amygdala. There is also a top-down modulation by DLPFC on the VMPFC-Amygdala connection. Craving contrast input only modulated amygdala directly. Using sliding-window for temporal evaluation, craving input to amygdala increased over time, simultaneously, DLPFC top-down modulatory effect on VMPFC-amygdala connection decreased. Temporal changes in the network connectivity during cue exposure with enhancement in craving input to amygdala and reduction in top-down modulatory effects of DLPFC, could provide us with new insights towards the dynamic nature of the cue-reactivity and failure to control its motivational consequences. Dynamic response of top-down regulatory networks during cue exposure can be considered as a new potential biomarker in the future addiction fMRI studies.

scholarly journals It is Never as Good the Second Time Around: Brain Areas Involved in Salience Processing Habituate During Repeated Drug Cue Exposure in Methamphetamine and Opioid Users

2020 ◽  
Author(s):  
Hamed Ekhtiari ◽  
Rayus Kuplicki ◽  
Robin P Aupperle ◽  
Martin P. Paulus
Keyword(s):  
Ventral Striatum ◽  
Temporal Dynamics ◽  
Cue Reactivity ◽  
Opioid Use ◽  
Brain Response ◽  
Cue Exposure ◽  
Addiction Medicine ◽  
Discovery Sample ◽  
Drug Cue ◽  
Clinical Populations

AbstractIntroductionThe brain response to drug-related cues is an important marker in addiction-medicine, however, the temporal dynamics of this response in repeated exposure to the cues are not well known yet. In an fMRI drug cue-reactivity task, the presence of rapid habituation or sensitization was investigated by modeling time and its interaction with condition (drug>neutral) using an initial discovery-sample. Replication of this temporal response was tested in two other clinical populations.MethodsSixty-five male participants (35.8±8.4 years-old) with methamphetamine use disorder (MUD) were recruited as the discovery-sample. A linear mixed effects model was used to identify areas with a time-by-condition interaction in the discovery-sample. Replication of these effects was tested in two other samples (29 female with MUD and 22 male with opioid use disorder). The second replication-sample was re-tested within two weeks.ResultsIn the discovery-sample, clusters within the VMPFC, amygdala and ventral striatum showed both significant condition and condition-by-time interaction with a habituation response for the drug-related cues but not neutral cues. The estimates for the main effects and interactions were generally consistent between the discovery and replication-samples across all clusters. The re-test data showed consistent lack of drug>neutral and habituation response within all selected clusters in the second cue-exposure session.ConclusionsVMPFC, amygdala and ventral striatum show a habituation in response to drug-related cues which is consistent among different clinical populations. Habituation in response in the first session of cue-exposure and lack of reactivity in the second session of exposure provide foundations for development of cue-desensitization interventions.

scholarly journals Ordering global governance complexes: The evolution of the governance complex for international civil aviation

2021 ◽  
Author(s):  
Mette Eilstrup-Sangiovanni
Keyword(s):  
Global Governance ◽  
International Institutions ◽  
Historical Data ◽  
Civil Aviation ◽  
Top Down ◽  
Bottom Up ◽  
Governance Systems ◽  
Governance Effectiveness ◽  
Political Agents ◽  
Over Time

AbstractMany observers worry that growing numbers of international institutions with overlapping functions undermine governance effectiveness via duplication, inconsistency and conflict. Such pessimistic assessments may undervalue the mechanisms available to states and other political agents to reduce conflictual overlap and enhance inter-institutional synergy. Drawing on historical data I examine how states can mitigate conflict within Global Governance Complexes (GGCs) by dissolving or merging existing institutions or by re-configuring their mandates. I further explore how “order in complexity” can emerge through bottom-up processes of adaptation in lieu of state-led reform. My analysis supports three theoretical claims: (1) states frequently refashion governance complexes “top-down” in order to reduce conflictual overlap; (2) “top-down” restructuring and “bottom-up” adaptation present alternative mechanisms for ordering relations among component institutions of GGCs; (3) these twin mechanisms ensure that GGCs tend to (re)produce elements of order over time–albeit often temporarily. Rather than evolving towards ever-greater fragmentation and disorder, complex governance systems thus tend to fluctuate between greater or lesser integration and (dis)order.

Precarity Unbound

2007 ◽  
Vol 32 (3) ◽  
pp. 319-340 ◽  
Author(s):  
Nancy Ettlinger
Keyword(s):  
Everyday Life ◽  
Final Section ◽  
Multiple Scales ◽  
Bush Administration ◽  
Radical Democracy ◽  
Top Down ◽  
Hardt And Negri ◽  
Global Events ◽  
Time Periods ◽  
Over Time

Departing from tendencies to bound precarity in particular time periods and world regions, this article develops an expansive view of precarity over time and across space. Beyond effects of specific global events and macroscale structures, precarity inhabits the microspaces of everyday life. However, people attempt to disengage the stress of precarious life by constructing the illusion of certainty. Reflexive denial of precarious life entails essentialist strategies that implicitly or explicitly classify and homogenize people and phenomena, legitimize the constructed boundaries, and in the process aim at eliminating difference and possibilities for negotiation; the tension between these goals and material realities helps explain misrepresentations that can be catastrophic at multiple scales, re-creating precarity. Reactions to 9/11 by the Bush administration represent a case in point of reflexive denial of precarity through strategies that created illusions of certainty with deleterious results. Normatively, the paradox of precarious life and reflexive denials prompts questions as to how urges for certainty in the context of precarity might be constructively channeled. the author approaches this challenge in the final section by drawing from a nexus of concerns about post-Habermasian radical democracy, individual thought and feeling, and network dynamics. Whereas Hardt and Negri reverse the direction of the Foucauldian concept of biopower from top-down to bottom-up, the author draws from Foucault's concept of governmentality in relation to resistance to imagine a cooperative politics operating within as well as across scales.

scholarly journals On attracting sets in artificial networks: cross activation

2018 ◽  
Vol 16 ◽  
pp. 01005
Author(s):  
Felix Sadyrbaev
Keyword(s):  
Dynamical Systems ◽  
Differential Equations ◽  
Mathematical Models ◽  
Ordinary Differential Equations ◽  
Critical Points ◽  
Regulatory Networks ◽  
Main Diagonal ◽  
Sigmoidal Function ◽  
Genomic Regulatory Networks ◽  
Over Time

Mathematical models of artificial networks can be formulated in terms of dynamical systems describing the behaviour of a network over time. The interrelation between nodes (elements) of a network is encoded in the regulatory matrix. We consider a system of ordinary differential equations that describes in particular also genomic regulatory networks (GRN) and contains a sigmoidal function. The results are presented on attractors of such systems for a particular case of cross activation. The regulatory matrix is then of particular form consisting of unit entries everywhere except the main diagonal. We show that such a system can have not more than three critical points. At least n–1 eigenvalues corresponding to any of the critical points are negative. An example for a particular choice of sigmoidal function is considered.

Kognitive Kontrolle der Aufmerksamkeitsintensität:

2004 ◽  
Vol 212 (2) ◽  
pp. 107-114
Author(s):  
Walter Sturm
Keyword(s):  
Top Down ◽  
Down Regulation

Zusammenfassung. Netzwerke zur kognitiven Kontrolle der Aufmerksamkeitsintensität regeln sowohl kurzfristig das Aktivierungs-(Alertness-)Niveau als auch die längerfristige Aufrechterhaltung dieses Aktivierungszustandes selbst in sehr monotonen Aufgabensituationen (Vigilanz). Funktionelle PET- oder fMRI-Bildgebungsstudien haben ein überwiegend rechtshemispärisches kortiko-subkortikales Netzwerk zur “top down“ Regulation der Aufmerksamkeitsintensität ergeben, welches sowohl die “intrinsische“ Alertness als auch die längerfristige Aufrechterhaltung der Aufmerksamkeit kontrolliert. Beteiligt sind sowohl der anteriore cinguläre als auch der dorsolaterale präfrontale und der inferiore parietale Kortex, welche über thalamische Kerne die vom Hirnstamm kommende Aktivierung regeln und “kanalisieren“. Diese Netzwerke scheinen supramodal zu sein und wurden bisher für visuelle und auditive sowie ansatzweise auch für somatosensorische Stimuli nachgewiesen. Die Regelung der Aufmerksamkeitsintensität ist auch Voraussetzung für eine energetische Versorgung komplexerer Aufmerksamkeitsleistungen wie Selektivität, räumliche Ausrichtung der Aufmerksamkeit und die Fähigkeit zur Aufmerksamkeitsteilung.

scholarly journals Transcranial Direct Current Stimulation to Modulate fMRI Drug Cue Reactivity in Methamphetamine Users: A Randomized Clinical Trial

2021 ◽  
Author(s):  
Hamed Ekhtiari ◽  
Ghazaleh Soleimani ◽  
Rayus Kuplicki ◽  
Hung-Wen Yeh ◽  
Yoon-Hee Cha ◽  
...  
Keyword(s):  
Clinical Trial ◽  
Direct Current ◽  
Transcranial Direct Current Stimulation ◽  
Cue Reactivity ◽  
Methamphetamine Use ◽  
Sham Stimulation ◽  
Group Time ◽  
Methamphetamine Use Disorder ◽  
The Brain ◽  
Drug Cue

Transcranial direct current stimulation (tDCS) has been studied as an adjunctive therapeutic option to alter maladaptive cortical excitability, activity, and connectivity associated with chronic substance use via the application of a weak direct current through the brain. The underlying mechanism of action remains ambiguous, however. We present a randomized, triple-blind, sham-controlled, clinical trial with two parallel arms conducted to determine the neural substrates of tDCS effects on drug craving using an fMRI drug cue reactivity paradigm. Sixty participants with methamphetamine use disorder were randomly assigned to two groups: 30 participants to active tDCS (5x7 cm2, 2 mA, for 20 minutes, anode/cathode over the F4/Fp1 in EEG 10-20 standard system) and 30 participants to the sham group. Neuroimaging data of a methamphetamine cue reactivity (MCR) task were collected immediately before and after stimulation with subjective craving assessed before, after, and during fMRI scans. There was a significant reduction in self-reported craving after stimulation (main effect of time) without any significant effect of group, time, or by group-time interaction. Our whole-brain analysis demonstrated that brain activation decreased in all parts of the brain in the second (post-stimulation) MCR imaging session after sham stimulation (habituation) but this uniform decrease did not occur throughout the brain in the active group. There were significant interactions between the group (active vs. sham) and time (after vs. before stimulation) in five main regions; medial frontal gyrus, anterior insula, inferior parietal lobule, precuneus, and inferior frontal gyrus with higher activations after active stimulation. We simulated computational head models for each individual. There was a significant effect of group in the relationship between level of current in the above-mentioned significant clusters and changes in task-modulated activation. We also found that brain regions with the highest electric fields in the prefrontal cortex showed a significant time by group interaction in task-modulated connectivity (psychophysiological interaction during MCR) in the frontoparietal network. In this two-parallel-arms triple-blind randomized control trial, we did not find any significant effect of the one session of active F4/Fp1 tDCS on drug craving self-report compared to sham stimulation. However, connectivity differences induced by active compared to sham stimulation suggested some potential mechanisms of tDCS to modulate neural response to drug cues among people with methamphetamine use disorder.

scholarly journals Eating behavior in response to food-cue exposure: Examining the cue-reactivity and counteractive-control models.

2009 ◽  
Vol 23 (1) ◽  
pp. 131-139 ◽  
Author(s):  
Jennifer S. Coelho ◽  
Anita Jansen ◽  
Anne Roefs ◽  
Chantal Nederkoorn
Keyword(s):  
Eating Behavior ◽  
Cue Reactivity ◽  
Cue Exposure ◽  
Control Models
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