scholarly journals Resting state functional coupling between the ascending synchronising system, limbic system and the default mode network via theta oscillations

2016 ◽  
Author(s):  
Parnesh Raniga ◽  
Bryan Paton ◽  
Gary F. Egan
Keyword(s):  
Magnetic Resonance Imaging ◽  
Magnetic Resonance ◽  
Default Mode Network ◽  
Resting State ◽  
Theta Oscillations ◽  
Parahippocampal Gyrus ◽  
Functional Coupling ◽  
Resonance Imaging ◽  
Default Mode

AbstractIn order to better understand dysfunction in dementia and psychiatric illnesses, the underlying neuronal systems that give rise to normal memory and cognitive processes need to be better understood. Based on electrophysiological recordings in animals, theta oscillations have been proposed as an intrinsic mechanism for the orchestration of memory functions, especially episodic and autobiographical memory. Theta oscillations are controlled by the ascending synchronising system, a set of nucleui in the pontine tegmentum and basal forebrain. At a network level, the default mode network has been shown to be responsible for episodic and autobiographical.Using resting state fMRI data, we show using an ICA approach, seed based connectivity and dynamic causal modelling that the ascending synchronising system is coupled to the medial temporal lobe nodes including the hippocampus and parahippocampal gyrus and with the default mode network. Our results provide thus support the role of theta oscillations in memory function and coordination at a network level.HighlightsResting state functional coupling between the DMN, MTL and ascending synchronising system.Theta oscillations may be the basis of this coupling given the role of these structures in control of theta.Theta oscillations have been implicated in memory, cognition and predictive coding.DMN, MTL and ASS are implicated in Alzheimer’s disease.AbbreviationsMRIMagnetic resonance imagingfMRIfunctional magnetic resonance imagingrs-fmriresting state functional magnetic resonance imagingPnOPontine nucleus oralisSuMSupra-mamillary nucleus.MSMedial septumDBDiagonal band of Broca.VTAventral tegmental areaPCCPosterior cingulate cortexHCHippocampusARASAscending reticular activating systemASSAscending synchronising systemDMNDefault Mode NetworkaMPFCAnterior Medial Prefrontal CortexpIPLPosterior inferior parietal lobuleNBMNucleus Basalis MynertDCMDynamic causal modellingPHGParahippocampal Gyrus

scholarly journals Role of the default mode network in cognitive transitions

2018 ◽  
Author(s):  
Verity Smith ◽  
Daniel J Mitchell ◽  
John Duncan
Keyword(s):  
Magnetic Resonance Imaging ◽  
Magnetic Resonance ◽  
Functional Magnetic Resonance Imaging ◽  
Default Mode Network ◽  
Task Switch ◽  
Thought Processes ◽  
Functional Magnetic Resonance ◽  
Resonance Imaging ◽  
Default Mode

ABSTRACTA frequently repeated finding is that the default mode network (DMN) shows activation decreases during externally-focused tasks. This finding has led to an emphasis in DMN research on internally-focused self-relevant thought processes. A recent study, in contrast, implicates the DMN in substantial externally-focused task switches. Using functional magnetic resonance imaging, we scanned 24 participants performing a task switch experiment. Whilst replicating previous DMN task switch effects, we also found large DMN increases for brief rests as well as task restarts after rest. Our findings are difficult to explain using theories strictly linked to internal or self-directed cognition. In line with principal results from the literature, we suggest that the DMN encodes scene, episode or context, by integrating spatial, self-referential and temporal information. Context representations are strong at rest, but re-reference to context also occurs at major cognitive transitions.

Altered Functional Connectivity within Default Mode Network in Patients with Transient Ischemic Attack: A Resting-State Functional Magnetic Resonance Imaging Study

2019 ◽  
Vol 48 (1-2) ◽  
pp. 61-69 ◽  
Author(s):  
Tingting Zhu ◽  
Lingyu Li ◽  
Yulin Song ◽  
Yu Han ◽  
Chengshu Zhou ◽  
...  
Keyword(s):  
Magnetic Resonance Imaging ◽  
Magnetic Resonance ◽  
Functional Connectivity ◽  
Functional Magnetic Resonance Imaging ◽  
Transient Ischemic Attack ◽  
Default Mode Network ◽  
Resting State ◽  
Functional Magnetic Resonance ◽  
Resonance Imaging ◽  
Ischemic Attack

Default mode network (DMN) is an important functional brain network that supports aspects of cognition. Stroke has been reported to be associated with functional connectivity (FC) impairments within DMN. However, whether FC within DMN changes in transient ischemic attack (TIA), an important risk factor for stroke, remains unclear. Forty-eight TIA patients and 41 age- and sex-matched healthy controls (HCs) were recruited in this study. Using resting-state functional magnetic resonance imaging seed-based FC methods, we examined FC alterations within DMN in TIA patients, tested its associations with clinical information, and further explored the ability of FC abnormalities to predict follow-up ischemic attacks. We found significantly decreased FC of left middle temporal gyrus/angular gyrus both with medial prefrontal cortex (mPFC) and posterior cingulate cortex/precuneus (PCC/Pcu) and significantly decreased FC among each pair of mPFC, left PCC, and right Pcu in patients with TIA as compared with HCs. Moreover, the connectivity between mPFC and left PCC could predict future ischemic attacks of the patients. Collectively, these findings may provide insights into further understanding of the underlying pathological mechanism in TIA, and aberrant FC between the hubs within DMN may provide a reference for the imaging diagnosis and early intervention of TIA.

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