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Chirumamilla, V. C.

Publications and source records attributed to Chirumamilla, V. C..

2 recordsLinked to original sources

Community driven dynamics of oscillatory network responses to threat

Physiological responses to threat stimuli involve neural synchronized oscillations in cerebral networks with distinct organization properties. Community architecture within these networks and its dynamic adaptation could play a critical role in achieving optimal physiological responses.\n\nHere we applied dynamic network analyses to address the early phases of threat processing at the millisecond level, describing multi-frequency (theta and alpha) integration and basic reorganization properties (flexibility and clustering) that drive physiological responses. We quantified cortical and subcortical network interactions and captured illustrative reconfigurations using community allegiance as essential fingerprints of large-scale adaptation.\n\nA theta band driven community reorganization of key anatomical regions forming the threat network (TN) along with transitions of nodes from the dorsal attention (DAN) and salience (SN) circuits predict the optimal physiological response to threat. We show that increase flexibility of the community network architecture drives the physiological responses during instructed threat processing. Nodal switches modulate the directionality of information flows in the involved circuits.\n\nThese results provide a captivating perspective of flexible network responses to threat and shed new light on basic physiological principles relevant for the development of stress- and threat-related mental disorders.

neuroscience↗

Excitability regulation in the dorsomedial prefrontal cortex during sustained instructed fear responses: a TMS-EEG study

BackgroundThreat detection is essential for protecting individuals from precarious situations. Early studies suggested a network of amygdala, limbic regions and dorsomedial prefrontal cortex (dmPFC) involved in fear processing. Excitability regulation in the dmPFC might be crucial for physiological fear processing, while an abnormal excitability pattern could lead to mental illness. Non-invasive paradigms to measure excitability regulation during fear processing in humans are missing.\n\nMethodsWe adapted an experimental approach of excitability characterization using electroencephalography (EEG) recordings and transcranial magnetic stimulation (TMS) over the dmPFC during an instructed fear paradigm to dynamically dissect its role in fear processing. Event-related (ERP) and TMS-evoked potentials (TEP) were analyzed to trace dmPFC excitability in healthy young volunteers (n = 40, age = 27.6 {+/-} 5.7 years, 22 females). Moreover, we linked the excitability regulation patterns to individual structural MRI-derived properties of gray matter microstructural integrity of the fear network.\n\nResultsAn increased cortical excitability was demonstrated in the threat (T) condition in comparison to no-threat (NT) as showed by increased amplitude of evoked potentials. Furthermore, TMS over the dmPFC induced markedly increased evoked responses during T condition in relation to NT. Moreover, we found that the structural integrity of the dmPFC and the amygdala predict excitability regulation patterns as measured by ERP and TEP during fear processing.\n\nConclusionsWe describe the dynamic range of excitability regulation in dmPFC during fear processing. The applied paradigm can be used to non-invasively track response abnormalities to threat stimuli in healthy subjects or patients with mental disorders.

neuroscience↗