scholarly journals Modelling Theta-Band Connectivity Between Occipital and Frontal Lobes: A Methodological MEG Study

2017 ◽  
Author(s):  
Darren Price ◽  
Matthew J. Brookes ◽  
Elizabeth B. Liddle ◽  
Peter F. Liddle ◽  
Lena Palaniyappan ◽  
...  
Keyword(s):  
Wave Propagation ◽  
Clinical Sample ◽  
Effective Connectivity ◽  
Travelling Wave ◽  
Task Demands ◽  
Modern Theory ◽  
Theta Band ◽  
Cortical Dynamics ◽  
Plausible Model ◽  
Cortical Regions

AbstractMeasuring functional connectivity between cortical regions of the human brain has become an important area of research. Modern theory suggests that brain networks exhibit non-stationarity, constantly forming and reforming depending on task demands. A robust means of determining effective connectivity in the short-lived neural responses that occur in event related paradigms would allow the investigation of event related cortico-cortical dynamics. We present such a mathematical model of wave propagation, motivated by current neuroscience literature, and demonstrate the utility of the method in a clinical sample of schizophrenia patients. MEG data were acquired in 10 patients with schizophrenia and 12 healthy controls during a relevance modulation task. Data were filtered into the theta band (4-8Hz) and source localised using a beamformer. The model was implemented using Fourier analysis methods which uncovered an event related travelling wave moving from the visual to frontal cortices. The model was validated using Monte Carlo phase randomisation and compared with another plausible model of wave propagation in the cortex. Results from the clinical sample revealed that wave speed was modulated by task condition and patients were found to have less difference between conditions (ANOVA revealing a significant interaction between group and condition, p<0.05). In conclusion, our method provides a simple and robust means to investigate event related cortico-cortical brain dynamics in individuals and groups in the task positive state.

scholarly journals Task-Modulated Corticocortical Synchrony in the Cognitive-Motor Network Supporting Handwriting

2019 ◽  
Vol 30 (3) ◽  
pp. 1871-1886
Author(s):  
Timo Saarinen ◽  
Jan Kujala ◽  
Hannu Laaksonen ◽  
Antti Jalava ◽  
Riitta Salmelin
Keyword(s):  
Large Scale ◽  
Phase Synchronization ◽  
Task Demands ◽  
Low Frequencies ◽  
Simple Loop ◽  
Cortical Dynamics ◽  
Motor Network ◽  
Neural Processes ◽  
Hand Coordination ◽  
Cortical Regions

Abstract Both motor and cognitive aspects of behavior depend on dynamic, accurately timed neural processes in large-scale brain networks. Here, we studied synchronous interplay between cortical regions during production of cognitive-motor sequences in humans. Specifically, variants of handwriting that differed in motor variability, linguistic content, and memorization of movement cues were contrasted to unveil functional sensitivity of corticocortical connections. Data-driven magnetoencephalography mapping (n = 10) uncovered modulation of mostly left-hemispheric corticocortical interactions, as quantified by relative changes in phase synchronization. At low frequencies (~2–13 Hz), enhanced frontoparietal synchrony was related to regular handwriting, whereas premotor cortical regions synchronized for simple loop production and temporo-occipital areas for a writing task substituting normal script with loop patterns. At the beta-to-gamma band (~13–45 Hz), enhanced synchrony was observed for regular handwriting in the central and frontoparietal regions, including connections between the sensorimotor and supplementary motor cortices and between the parietal and dorsal premotor/precentral cortices. Interpreted within a modular framework, these modulations of synchrony mainly highlighted interactions of the putative pericentral subsystem of hand coordination and the frontoparietal subsystem mediating working memory operations. As part of cortical dynamics, interregional phase synchrony varies depending on task demands in production of cognitive-motor sequences.

scholarly journals EEG Signal Diversity Varies With Sleep Stage and Aspects of Dream Experience

2021 ◽  
Vol 12 ◽  
Author(s):  
Arnfinn Aamodt ◽  
André Sevenius Nilsen ◽  
Benjamin Thürer ◽  
Fatemeh Hasanzadeh Moghadam ◽  
Nils Kauppi ◽  
...  
Keyword(s):  
Rem Sleep ◽  
Sleep Stage ◽  
Eeg Signal ◽  
Complexity Measures ◽  
Posterior Cortex ◽  
Cortical Dynamics ◽  
Dream Report ◽  
Signal Diversity ◽  
Cortical Regions ◽  
Integrated Information Theory

Several theories link consciousness to complex cortical dynamics, as suggested by comparison of brain signal diversity between conscious states and states where consciousness is lost or reduced. In particular, Lempel-Ziv complexity, amplitude coalition entropy and synchrony coalition entropy distinguish wakefulness and REM sleep from deep sleep and anesthesia, and are elevated in psychedelic states, reported to increase the range and vividness of conscious contents. Some studies have even found correlations between complexity measures and facets of self-reported experience. As suggested by integrated information theory and the entropic brain hypothesis, measures of differentiation and signal diversity may therefore be measurable correlates of consciousness and phenomenological richness. Inspired by these ideas, we tested three hypotheses about EEG signal diversity related to sleep and dreaming. First, diversity should decrease with successively deeper stages of non-REM sleep. Second, signal diversity within the same sleep stage should be higher for periods of dreaming vs. non-dreaming. Third, specific aspects of dream contents should correlate with signal diversity in corresponding cortical regions. We employed a repeated awakening paradigm in sleep deprived healthy volunteers, with immediate dream report and rating of dream content along a thought-perceptual axis, from exclusively thought-like to exclusively perceptual. Generalized linear mixed models were used to assess how signal diversity varied with sleep stage, dreaming and thought-perceptual rating. Signal diversity decreased with sleep depth, but was not significantly different between dreaming and non-dreaming, even though there was a significant positive correlation between Lempel-Ziv complexity of EEG recorded over the posterior cortex and thought-perceptual ratings of dream contents.

Individual Differences in Mental Imagery Modulate Effective Connectivity of Scene-Selective Regions During Resting State

2021 ◽  
Author(s):  
Maria Giulia Tullo ◽  
Hannes Almgren ◽  
Frederik Van de Steen ◽  
Valentina Sulpizio ◽  
Daniele Marinazzo ◽  
...  
Keyword(s):  
Individual Differences ◽  
Mental Imagery ◽  
Resting State ◽  
Effective Connectivity ◽  
Relevant Information ◽  
Brain Regions ◽  
Intrinsic Activity ◽  
Inhibitory Influence ◽  
Cortical Regions ◽  
Intrinsic Fluctuation

Abstract Successful navigation relies on the ability to identify, perceive, and correctly process the spatial structure of a scene. It is well known that visual mental imagery plays a crucial role in navigation. Indeed, cortical regions encoding navigationally relevant information are also active during mental imagery of navigational scenes. However, it remains unknown whether their intrinsic activity and connectivity reflect the individuals’ ability to imagine a scene. Here, we primarily investigated the intrinsic causal interactions among scene-selective brain regions such as Parahipoccampal Place Area (PPA), Retrosplenial Complex (RSC), and Occipital Place Area (OPA) using Dynamic Causal Modelling (DCM) for resting-state functional magnetic resonance (rs-fMRI) data. Second, we tested whether resting-state effective connectivity parameters among scene-selective regions could reflect individual differences in mental imagery in our sample, as assessed by the self-reported Vividness of Visual Imagery Questionnaire (VVIQ). We found an inhibitory influence of occipito-medial on temporal regions, and an excitatory influence of more anterior on more medial and posterior brain regions. Moreover, we found that a key role in imagery is played by the connection strength from OPA to PPA, especially in the left hemisphere, since the influence of the signal between these scene-selective regions positively correlated with good mental imagery ability. Our investigation contributes to the understanding of the complexity of the causal interaction among brain regions involved in navigation and provides new insight in understanding how an essential ability, such as mental imagery, can be explained by the intrinsic fluctuation of brain signal.

scholarly journals Asymmetric gravity–capillary solitary waves on deep water

2014 ◽  
Vol 759 ◽  
Author(s):  
Z. Wang ◽  
J.-M. Vanden-Broeck ◽  
P. A. Milewski
Keyword(s):  
Wave Propagation ◽  
Solitary Waves ◽  
Travelling Wave ◽  
Propagation Direction ◽  
Travelling Wave Solutions ◽  
Two Dimensional ◽  
Bifurcation Curve ◽  
Wave Propagation Direction ◽  
Wave Solutions ◽  
Deep Fluid

AbstractWe present new families of gravity–capillary solitary waves propagating on the surface of a two-dimensional deep fluid. These spatially localised travelling-wave solutions are non-symmetric in the wave propagation direction. Our computation reveals that these waves appear from a spontaneous symmetry-breaking bifurcation, and connect two branches of multi-packet symmetric solitary waves. The speed–energy bifurcation curve of asymmetric solitary waves features a zigzag behaviour with one or more turning points.

443 EFFECTIVE CONNECTIVITY AND CORTICAL REGIONS INVOLVED IN TASK-RELATED BLADDER CONTROL

2010 ◽  
Vol 183 (4S) ◽  
Author(s):  
Moritz Hamann ◽  
Christoph Van der Horst ◽  
Stephan Wolff ◽  
Olaf Jansen ◽  
Klaus-Peter Juenemann ◽  
...  
Keyword(s):  
Effective Connectivity ◽  
Bladder Control ◽  
Cortical Regions

scholarly journals A thalamo-centric neural signature for restructuring negative self-beliefs

2022 ◽  
Author(s):  
Trevor Steward ◽  
Po-Han Kung ◽  
Christopher G. Davey ◽  
Bradford A. Moffat ◽  
Rebecca K. Glarin ◽  
...  
Keyword(s):  
Prefrontal Cortex ◽  
Emotional Reactivity ◽  
Effective Connectivity ◽  
Cognitive Restructuring ◽  
7 Tesla ◽  
Excitatory Effect ◽  
Negative Beliefs ◽  
Socratic Questioning ◽  
Major Shift ◽  
Cortical Regions

AbstractNegative self-beliefs are a core feature of psychopathology. Despite this, we have a limited understanding of the brain mechanisms by which negative self-beliefs are cognitively restructured. Using a novel paradigm, we had participants use Socratic questioning techniques to restructure negative beliefs during ultra-high resolution 7-Tesla functional magnetic resonance imaging (UHF 7 T fMRI) scanning. Cognitive restructuring elicited prominent activation in a fronto-striato-thalamic circuit, including the mediodorsal thalamus (MD), a group of deep subcortical nuclei believed to synchronize and integrate prefrontal cortex activity, but which has seldom been directly examined with fMRI due to its small size. Increased activity was also identified in the medial prefrontal cortex (MPFC), a region consistently activated by internally focused mental processing, as well as in lateral prefrontal regions associated with regulating emotional reactivity. Using Dynamic Causal Modelling (DCM), evidence was found to support the MD as having a strong excitatory effect on the activity of regions within the broader network mediating cognitive restructuring. Moreover, the degree to which participants modulated MPFC-to-MD effective connectivity during cognitive restructuring predicted their individual tendency to engage in repetitive negative thinking. Our findings represent a major shift from a cortico-centric framework of cognition and provide important mechanistic insights into how the MD facilitates key processes in cognitive interventions for common psychiatric disorders. In addition to relaying integrative information across basal ganglia and the cortex, we propose a multifaceted role for the MD whose broad excitatory pathways act to increase synchrony between cortical regions to sustain complex mental representations, including the self.

scholarly journals Task-related effective connectivity reveals that the cortical rich club gates cortex-wide communication

2017 ◽  
Author(s):  
Mario Senden ◽  
Niels Reuter ◽  
Martijn P. van den Heuvel ◽  
Rainer Goebel ◽  
Gustavo Deco ◽  
...  
Keyword(s):  
Information Exchange ◽  
Effective Connectivity ◽  
Functional Integration ◽  
Brain Regions ◽  
Rich Club ◽  
State Dependent ◽  
Gating Mechanism ◽  
The Rich ◽  
Cortical Regions ◽  
Peripheral Regions

AbstractHigher cognition may require the globally coordinated integration of specialized brain regions into functional networks. A collection of structural cortical hubs - referred to as the rich club - has been hypothesized to support task-specific functional integration. In the present paper, we use a whole-cortex model to estimate directed interactions between 68 cortical regions from fMRI activity for four different tasks (reflecting different cognitive domains) and resting state. We analyze the state-dependent input and output effective connectivity of the structural rich club and relate these to whole-cortex dynamics and network reconfigurations. We find that the cortical rich club exhibits an increase in outgoing effective connectivity during task performance as compared to rest while incoming connectivity remains constant. Increased outgoing connectivity targets a sparse set of peripheral regions with specific regions strongly overlapping between tasks. At the same time, community detection analyses reveal massive reorganizations of interactions among peripheral regions, including those serving as target of increased rich club output. This suggests that while peripheral regions may play a role in several tasks, their concrete interplay might nonetheless be task-specific. Furthermore, we observe that whole-cortex dynamics are faster during task as compared to rest. The decoupling effects usually accompanying faster dynamics appear to be counteracted by the increased rich club outgoing effective connectivity. Together our findings speak to a gating mechanism of the rich club that supports fast-paced information exchange among relevant peripheral regions in a task-specific and goal-directed fashion, while constantly listening to the whole network.

scholarly journals FDTD analysis of transient fault induced travelling-wave propagation for multi-branch distribution networks

2020 ◽  
Vol 33 ◽  
pp. 124-129
Author(s):  
Baiyang Liu ◽  
Minqiang Li ◽  
Chen Wang ◽  
Kun Yu ◽  
Yongze Wu ◽  
...  
Keyword(s):  
Wave Propagation ◽  
Distribution Networks ◽  
Travelling Wave ◽  
Transient Fault ◽  
Branch Distribution
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