Synchronization in the connectome: Metastable oscillatory modes emerge from interactions in the brain spacetime network

A rich repertoire of oscillatory signals is detected from human brains with electro- and magnetoencephalography (EEG/MEG). However, the principles underwriting coherent oscillations and their link with neural activity remain unclear. Here, we hypothesise that the emergence of transient brain rhythms is a signature of weakly stable synchronization between spatially distributed brain areas, occurring at network-specific collective frequencies due to non-negligible conduction times. We test this hypothesis using a phenomenological network model to simulate interactions between neural mass potentials (resonating at 40Hz) in the structural connectome. Crucially, we identify a critical regime where metastable oscillatory modes emerge spontaneously in the delta (0.5-4Hz), theta (4-8Hz), alpha (8-13Hz) and beta (13-30Hz) frequency bands from weak synchronization of subsystems, closely approximating the MEG power spectra from 89 healthy individuals. Grounded in the physics of delay-coupled oscillators, these numerical analyses demonstrate the role of the spatiotemporal connectome in structuring brain activity in the frequency domain.

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Language and Math: What If We Have Two Separate Naming Systems?

Languages ◽

10.3390/languages4030068 ◽

2019 ◽

Vol 4 (3) ◽

pp. 68

Author(s):

Alejandro Martínez

Keyword(s):

Switch Cost ◽

Brain Activity ◽

Spanish Speakers ◽

Brain Areas ◽

Exact Arithmetic ◽

Source Estimation ◽

Numerical Representations ◽

The Impact ◽

The Brain

The role of language in numerical processing has traditionally been restricted to counting and exact arithmetic. Nevertheless, the impact that each of a bilinguals’ languages may have in core numerical representations has not been questioned until recently. What if the language in which math has been first acquired (LLmath) had a bigger impact in our math processing? Based on previous studies on language switching we hypothesize that balanced bilinguals would behave like unbalanced bilinguals when switching between the two codes for math. In order to address this question, we measured the brain activity with magneto encephalography (MEG) and source estimation analyses of 12 balanced Basque-Spanish speakers performing a task in which participants were unconscious of the switches between the two codes. The results show an asymmetric switch cost between the two codes for math, and that the brain areas responsible for these switches are similar to those thought to belong to a general task switching mechanism. This implies that the dominances for math and language could run separately from the general language dominance.

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Limbic Expression of mRNA Coding for Chemoreceptors in Human Brain—Lessons from Brain Atlases

International Journal of Molecular Sciences ◽

10.3390/ijms22136858 ◽

2021 ◽

Vol 22 (13) ◽

pp. 6858

Author(s):

Fanny Gaudel ◽

Gaëlle Guiraudie-Capraz ◽

François Féron

Keyword(s):

G Proteins ◽

The Body ◽

Trace Amines ◽

Chemical Senses ◽

Brain Areas ◽

Genes Encoding ◽

The Central Nervous System ◽

Human Brains ◽

The Brain ◽

Brain Atlases

Animals strongly rely on chemical senses to uncover the outside world and adjust their behaviour. Chemical signals are perceived by facial sensitive chemosensors that can be clustered into three families, namely the gustatory (TASR), olfactory (OR, TAAR) and pheromonal (VNR, FPR) receptors. Over recent decades, chemoreceptors were identified in non-facial parts of the body, including the brain. In order to map chemoreceptors within the encephalon, we performed a study based on four brain atlases. The transcript expression of selected members of the three chemoreceptor families and their canonical partners was analysed in major areas of healthy and demented human brains. Genes encoding all studied chemoreceptors are transcribed in the central nervous system, particularly in the limbic system. RNA of their canonical transduction partners (G proteins, ion channels) are also observed in all studied brain areas, reinforcing the suggestion that cerebral chemoreceptors are functional. In addition, we noticed that: (i) bitterness-associated receptors display an enriched expression, (ii) the brain is equipped to sense trace amines and pheromonal cues and (iii) chemoreceptor RNA expression varies with age, but not dementia or brain trauma. Extensive studies are now required to further understand how the brain makes sense of endogenous chemicals.

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Consciousness, decision making, and volition: freedom beyond chance and necessity

Theory in Biosciences ◽

10.1007/s12064-021-00346-6 ◽

2021 ◽

Author(s):

Hans Liljenström

Keyword(s):

Decision Making ◽

Free Will ◽

Brain Activity ◽

Brain Structures ◽

Complex Process ◽

Neural Information ◽

Neural Information Processing ◽

Stochastic Population Model ◽

The Brain

AbstractWhat is the role of consciousness in volition and decision-making? Are our actions fully determined by brain activity preceding our decisions to act, or can consciousness instead affect the brain activity leading to action? This has been much debated in philosophy, but also in science since the famous experiments by Libet in the 1980s, where the current most common interpretation is that conscious free will is an illusion. It seems that the brain knows, up to several seconds in advance what “you” decide to do. These studies have, however, been criticized, and alternative interpretations of the experiments can be given, some of which are discussed in this paper. In an attempt to elucidate the processes involved in decision-making (DM), as an essential part of volition, we have developed a computational model of relevant brain structures and their neurodynamics. While DM is a complex process, we have particularly focused on the amygdala and orbitofrontal cortex (OFC) for its emotional, and the lateral prefrontal cortex (LPFC) for its cognitive aspects. In this paper, we present a stochastic population model representing the neural information processing of DM. Simulation results seem to confirm the notion that if decisions have to be made fast, emotional processes and aspects dominate, while rational processes are more time consuming and may result in a delayed decision. Finally, some limitations of current science and computational modeling will be discussed, hinting at a future development of science, where consciousness and free will may add to chance and necessity as explanation for what happens in the world.

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Cannabidiol Has a Unique Effect on Global Brain Activity: A Pharmacological, Functional MRI Study in Awake Mice

10.21203/rs.3.rs-253550/v1 ◽

2021 ◽

Author(s):

Aymen Sadaka ◽

Ana Ozuna ◽

Richard Ortiz ◽

Praveen Kulkarni ◽

Clare Johnson ◽

...

Keyword(s):

Prefrontal Cortex ◽

Brain Activity ◽

Stress Disorders ◽

Functional Coupling ◽

Specific Information ◽

Imaging Data ◽

Post Traumatic Stress ◽

Brain Areas ◽

Dose Dependent ◽

The Brain

Abstract Background: The phytocannabinoid cannabidiol (CBD) is a potential treatment for post-traumatic stress disorders. How does CBD interact with the brain to alter behavior? We hypothesized that CBD would produce a dose-dependent reduction in brain activity and functional coupling in neural circuitry associated with fear and defense. Methods: During the scanning session awake mice were given vehicle or CBD (3, 10, or 30 mg/kg I.P.) and imaged for 10 min post treatment. Mice were also treated with the 10 mg/kg dose of CBD and imaged one hr later for resting state BOLD functional connectivity (rsFC). Imaging data were registered to a 3D MRI mouse atlas providing site-specific information on 138 different brain areas. Blood samples were collected for CBD measurements.Results: CBD produced a dose-dependent polarization of activation along the rostral-caudal axis of the brain. The olfactory bulb and prefrontal cortex showed an increase in positive BOLD whereas the brainstem and cerebellum showed a decrease in BOLD signal. This negative BOLD affected many areas connected to the ascending reticular activating system (ARAS). The ARAS was decoupled to much of the brain but was hyperconnected to the olfactory system and prefrontal cortex. The pattern of ARAS connectivity closely overlapped with brain areas showing high levels N-acyl-phosphatidylethanolamines-specific phospholipase D (NAPE-PLD) messenger RNA.Conclusion: The CBD-induced decrease in ARAS activity is consistent with an emerging literature suggesting that CBD reduces autonomic arousal under conditions of emotional and physical stress. The putative target and mechanism of action is NAPE-PLD the enzyme responsible for the biosynthesis of lipid signaling molecules like anandamide.

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Neuronal spreading and plaque induction of intracellular Aβ and its disruption of Aβ homeostasis

Acta Neuropathologica ◽

10.1007/s00401-021-02345-9 ◽

2021 ◽

Author(s):

Tomas T. Roos ◽

Megg G. Garcia ◽

Isak Martinsson ◽

Rana Mabrouk ◽

Bodil Israelsson ◽

...

Keyword(s):

Brain Homogenate ◽

Fold Increase ◽

Amyloid Beta Peptide ◽

Intracellular Accumulation ◽

Brain Areas ◽

Cellular Models ◽

Beta Peptide ◽

The Brain

AbstractThe amyloid-beta peptide (Aβ) is thought to have prion-like properties promoting its spread throughout the brain in Alzheimer’s disease (AD). However, the cellular mechanism(s) of this spread remains unclear. Here, we show an important role of intracellular Aβ in its prion-like spread. We demonstrate that an intracellular source of Aβ can induce amyloid plaques in vivo via hippocampal injection. We show that hippocampal injection of mouse AD brain homogenate not only induces plaques, but also damages interneurons and affects intracellular Aβ levels in synaptically connected brain areas, paralleling cellular changes seen in AD. Furthermore, in a primary neuron AD model, exposure of picomolar amounts of brain-derived Aβ leads to an apparent redistribution of Aβ from soma to processes and dystrophic neurites. We also observe that such neuritic dystrophies associate with plaque formation in AD-transgenic mice. Finally, using cellular models, we propose a mechanism for how intracellular accumulation of Aβ disturbs homeostatic control of Aβ levels and can contribute to the up to 10,000-fold increase of Aβ in the AD brain. Our data indicate an essential role for intracellular prion-like Aβ and its synaptic spread in the pathogenesis of AD.

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Is Artistic Composition in Abstract Art Detected Automatically?

10.1093/oso/9780197513620.003.0021 ◽

2021 ◽

pp. 102-106

Author(s):

Claudia Menzel ◽

Gyula Kovács ◽

Gregor U. Hayn-Leichsenring ◽

Christoph Redies

Keyword(s):

Human Brain ◽

Significant Role ◽

Mismatch Negativity ◽

Brain Activity ◽

Perceptual Processing ◽

Abstract Art ◽

Electrical Brain Activity ◽

Image Set ◽

The Brain

Most artists who create abstract paintings place the pictorial elements not at random, but arrange them intentionally in a specific artistic composition. This arrangement results in a pattern of image properties that differs from image versions in which the same pictorial elements are randomly shuffled. In the article under discussion, the original abstract paintings of the author’s image set were rated as more ordered and harmonious but less interesting than their shuffled counterparts. The authors tested whether the human brain distinguishes between these original and shuffled images by recording electrical brain activity in a particular paradigm that evokes a so-called visual mismatch negativity. The results revealed that the brain detects the differences between the two types of images fast and automatically. These findings are in line with models that postulate a significant role of early (low-level) perceptual processing of formal image properties in aesthetic evaluations.

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High-frequency electrical activity of the brain in patients with hemispheric ischemic stroke in combination with cognitive functions

Russian neurological Journal ◽

10.30629/2658-7947-2020-25-6-12-18 ◽

2021 ◽

Vol 25 (6) ◽

pp. 12-18

Author(s):

L. B. Novikova ◽

K. M. Sharapova ◽

O. E. Dmitrieva

Keyword(s):

Ischemic Stroke ◽

Mathematical Analysis ◽

Depressive Disorders ◽

Brain Activity ◽

Power Spectra ◽

Peak Frequency ◽

Gamma Rhythm ◽

Eeg Data ◽

Background Eeg ◽

The Brain

Abstract. The mathematical analysis of electroencephalography (EEG) provides information about the functional state of the brain, expands the understanding of the mechanisms of interaction between different areas of the brain, increases the possibilities of diagnostics and allows to put forward new tasks in the field of studying brain activity. Aim. To assess changes in the gamma-rhythm in patients with hemispheric ischemic stroke in the most acute and acute periods in comparison with cognitive and anxiety-depressive disorders. Material and methods. The study included 32 patients with hemispheric ischemic stroke. All patients underwent complex clinical, neurological, instrumental and laboratory studies. The study and recording of the EEG was carried out on the 1st and 21st days of the disease, lasting 20 minutes. The method of mathematical analysis was used to estimate the power spectra and the peak frequency of the gamma — rhythm of the background EEG. Results. As a result of the study, it was found that cognitive and anxiety-depressive disorders are detected already in the most acute and acute periods of ischemic stroke. In the mathematical analysis of the EEG statistically significant correlations between the gamma — rhythm index and cognitive, anxiety-depressive disorders in the frontal, central temporal areas are noted. Conclusion. The complex of examination of patients should include, in addition to clinical and neuropsychological research, mathematical analysis of EEG data.

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Resting-state connectivity studies as a marker of the acute and delayed effects of subanaesthetic ketamine administration in healthy and depressed individuals: A systematic review

Brain and Neuroscience Advances ◽

10.1177/23982128211055426 ◽

2021 ◽

Vol 5 ◽

pp. 239821282110554

Author(s):

Vasileia Kotoula ◽

Toby Webster ◽

James Stone ◽

Mitul A Mehta

Keyword(s):

Resting State ◽

Emotional Regulation ◽

Brain Connectivity ◽

Brain Activity ◽

Reward Processing ◽

Brain Areas ◽

Delayed Effects ◽

Treatment Naïve ◽

Resting State Connectivity ◽

The Brain

Acute ketamine administration has been widely used in neuroimaging research to mimic psychosis-like symptoms. Within the last two decades, ketamine has also emerged as a potent, fast-acting antidepressant. The delayed effects of the drug, observed 2–48 h after a single infusion, are associated with marked improvements in depressive symptoms. At the systems’ level, several studies have investigated the acute ketamine effects on brain activity and connectivity; however, several questions remain unanswered around the brain changes that accompany the drug’s antidepressant effects and how these changes relate to the brain areas that appear with altered function and connectivity in depression. This review aims to address some of these questions by focusing on resting-state brain connectivity. We summarise the studies that have examined connectivity changes in treatment-naïve, depressed individuals and those studies that have looked at the acute and delayed effects of ketamine in healthy and depressed volunteers. We conclude that brain areas that are important for emotional regulation and reward processing appear with altered connectivity in depression whereas the default mode network presents with increased connectivity in depressed individuals compared to healthy controls. This finding, however, is not as prominent as the literature often assumes. Acute ketamine administration causes an increase in brain connectivity in healthy volunteers. The delayed effects of ketamine on brain connectivity vary in direction and appear to be consistent with the drug normalising the changes observed in depression. The limited number of studies however, as well as the different approaches for resting-state connectivity analysis make it very difficult to draw firm conclusions and highlight the importance of data sharing and larger future studies.

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Complex of global functional network as the core of consciousness

10.31234/osf.io/89ugz ◽

2021 ◽

Author(s):

Keiichi Onoda

Keyword(s):

Dynamic System ◽

Brain Activity ◽

Posterior Part ◽

Neural Basis ◽

Attention Networks ◽

The Core ◽

Hierarchical Partition ◽

Brain Fmri ◽

The Brain

Finding the neural basis of consciousness is a challenging issue, and it is still inconclusive where the core of consciousness is distributed in the brain. The global neuronal workspace theory (GNWT) emphasizes the role of the frontoparietal regions, whereas the integrated information theory (IIT) argues that the posterior part of the brain is the core of consciousness. IIT has proposed “main complex” as the core of consciousness in a dynamic system, which is a set of elements that the information loss in a hierarchical partition approach is the largest among that of all its supersets and subsets. However, no experimental study has reported the core of consciousness using the main complex for actual brain activity. This study estimated the main complex of brain dynamics using a functional MRI. The whole-brain fMRI data of eight conditions (seven tasks and a rest state) were divided into multiple elements based on network atlases, and the main complex of the dynamic system was estimated for each condition. It is assumed that, if there is a set of elements in the complex that are common to all conditions, the set is likely to contain the core of consciousness. Executive control, salience, and dorsal/ventral attention networks were commonly included in the main complex across all conditions, implying that these networks are responsible for the core of consciousness. This finding is consistent with the GNWT, as these networks are across the prefrontal and parietal regions.

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Collective excitability in a mesoscopic neuronal model of epileptic activity

10.1101/162636 ◽

2017 ◽

Cited By ~ 1

Author(s):

Maciej Jedynak ◽

Antonio J. Pons ◽

Jordi Garcia-Ojalvo

Keyword(s):

Neuronal Model ◽

Epileptic Activity ◽

Brain Areas ◽

Sustained Activity ◽

Collective Activity ◽

Neural Mass ◽

Joint Dynamics ◽

Coupling Strengths ◽

Neuronal Oscillators ◽

The Brain

The brain can be understood as a collection of interacting neuronal oscillators, but the extent to which its sustained activity is due to coupling among brain areas is still unclear. Here we study the joint dynamics of two cortical columns described by Jansen-Rit neural mass models, and show that coupling between the columns gives rise to stochastic initiations of sustained collective activity, which can be interpreted as epileptic events. For large enough coupling strengths, termination of these events results mainly from the emergence of synchronization between the columns, and thus is controlled by coupling instead of noise. Stochastic triggering and noise-independent durations are characteristic of excitable dynamics, and thus we interpret our results in terms of collective excitability.

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