Hamiltonian energy computation and complex behavior of a small heterogeneous network of three neurons: circuit implementation

Brain functions are sometimes emulated using some analog integrated circuits based on the organizational principle of natural neural networks. Neuromorphic engineering is the research branch devoted to the study and realization of such circuits with striking features. In this contribution, a novel small network of three neurons is introduced and investigated. The model is built from the coupling between two 2D Hindmarsh–Rose neurons through a 2D FitzHugh–Nagumo neuron. Thus, a heterogeneous coupled network is obtained. The biophysical energy released by the network during each electrical activity is evaluated. In addition, nonlinear analysis tools such as two-parameter Lyapunov exponent, bifurcation diagrams, the graph of the largest Lyapunov exponent, phase portraits, time series, as well as the basin of attractions are used to numerically investigate the network. It is found that the model can experience hysteresis justified by the simultaneous existence of three distinct electrical activities using the same set of parameters. Finally, the circuit implementation of the network is addressed in PSPICE to further support the obtained results.

Intra-individual Physiomic Landscape of Pyramidal Neurons in the Human Neocortex

Computation within cortical microcircuits is determined by functional properties of the neurons and their synaptic interactions. While heterogeneity of inhibitory interneurons is well established, the anatomical, physiological, and molecular differentiation of excitatory pyramidal neurons is not fully resolved. To identify functional subtypes within the pyramidal neuron population, we focused on human layer 2-3 cortex which greatly expanded during evolution. We performed multi-neuron patch-clamp recordings in brain slices from the temporal cortex of 22 epilepsy patients. We characterized the electrophysiological properties of up to 80 pyramidal neurons per patient, enabling us to assess inter- and intra-individual functional variability. Hierarchical clustering of the high-dimensional parameter space yielded functionally distinct clusters of pyramidal neurons which were present across individuals. This may represent a generic organizational principle converging with previously described transcriptomic heterogeneity. We further observed substantial heterogeneity in physiological parameters with intra-individual variability being severalfold larger than inter-individual variability. The phenotypic variability within and across pyramidal neuron subtypes has important implications for the computational capacity of the cortical microcircuit.

Intrinsic timescales as an organizational principle of neural processing across the whole rhesus macaque brain

Hierarchical temporal dynamics are a fundamental computational property of the brain; however, there are no whole-brain, noninvasive investigations into timescales of neural processing in animal models. To that end, we used the spatial resolution and sensitivity of ultra-high field fMRI to probe timescales across the whole macaque brain. We uncovered within-species consistency between timescales estimated from fMRI and electrophysiology. Crucially, we were not only able to demonstrate that we can replicate existing electrophysiological hierarchies, but we extended these to whole brain topographies. Our results validate the complementary use of hemodynamic and electrophysiological intrinsic timescales, establishing a basis for future translational work. Second, with those results in hand, we were able to show that one facet of the high-dimensional FC topography of any region in the brain is closely related to hierarchical temporal dynamics. We demonstrated that intrinsic timescales are organized along spatial gradients that closely match functional connectivity gradient topographies across the whole brain. We conclude that intrinsic timescales are an unifying organizational principle of neural processing across the whole brain.

Exploring electroencephalography with a model inspired by quantum mechanics

An outstanding issue in cognitive neuroscience concerns how the brain is organized across different conditions. For instance, during the resting-state condition, the brain can be clustered into reliable and reproducible networks (e.g., sensory, default, executive networks). Interestingly, the same networks emerge during active conditions in response to various tasks. If similar patterns of neural activity have been found across diverse conditions, and therefore, different underlying processes and experiences of the environment, is the brain organized by a fundamental organizational principle? To test this, we applied mathematical formalisms borrowed from quantum mechanisms to model electroencephalogram (EEG) data. We uncovered a tendency for EEG signals to be localized in anterior regions of the brain during “rest”, and more uniformly distributed while engaged in a task (i.e., watching a movie). Moreover, we found analogous values to the Heisenberg uncertainty principle, suggesting a common underlying architecture of human brain activity in resting and task conditions. This underlying architecture manifests itself in the novel constant KBrain, which is extracted from the brain state with the least uncertainty. We would like to state that we are using the mathematics of quantum mechanics, but not claiming that the brain behaves as a quantum object.

Of Constitutions, Campaigns and Commissions: A Century of Democratic Centralism under the CCP

Democratic centralism, a hallmark of Leninist party organizations, has played a formative role in the history of the Chinese Communist Party (CCP). Yet despite being hailed as an “inviolable” and “unchanging” Party principle, understandings of democratic centralism have shifted dramatically over the century of its existence. This study traces the long arc of the concept's evolution across successive Party Constitutions, focusing on three critical historical junctures: the Sixth Party Congress, which formally adopted democratic centralism into its Constitution as an organizational principle; the Seventh Party Congress, which adopted rectification as the Party's practice of democratic centralism; and the 19th Party Congress, which set a new milestone in codifying the system as a disciplinary tool. I argue that while democratic centralism exemplifies the CCP's institutional plasticity and adaptive governance and is critical to understanding Party-driven constitutionalism in contemporary China, it also highlights an irresolvable paradox inherent in Party rule. Adaptability does not necessarily impart resilience. I conclude that the CCP's normatively unconstrained extra-constitutional leadership under Xi Jinping highlights the essentially and increasingly irrationalist aspects of its illiberal governance project.

High activity and high functional connectivity are mutually exclusive in resting state zebrafish and human brains

Active neurons impact cell types with which they are functionally connected. Both activity and functional connectivity are heterogeneous across the brain, but the nature of their relationship is not known. Here we employ brain-wide calcium imaging at cellular resolution in larval zebrafish to record spontaneous activity of >12,000 neurons in the forebrain. By classifying their activity and functional connectivity into three levels (high, medium, low), we find that highly active neurons have low functional connections and highly connected neurons are of low activity. Intriguingly, deploying the same analytical methods on functional magnetic resonance imaging (fMRI) data from the resting state human brain, we uncover a similar relationship between activity and functional connectivity, that is, regions of high activity are non-overlapping with those of high connectivity. These findings reveal a previously unknown and evolutionarily conserved brain organizational principle that have implications for understanding disease states and designing artificial neuronal networks.

The Molecular Logic Organizing the Functional Compartmentalization of Reciprocal Synapses

Reciprocal synapses are formed by neighboring dendritic processes that create the smallest possible neural circuit. Reciprocal synapses are widespread in brain and essential for information processing, but constitute a conceptual conundrum: How are adjacent pre- and post synaptic specializations maintained as separate functional units? Here, we reveal an organizational principle for reciprocal synapses, using dendrodendritic synapses between mitral and granule cells in the mouse olfactory bulb as a paradigm. We show that mitral cells secrete cerebellin-1 to block the cis-interaction of mitral cell neurexins with neuroligins, thereby enabling their separate trans-interactions. Ablating either cerebellin-1 or neuroligins in mitral cells severely impaired granule cell→mitral cell synapses, as did overexpression of postsynaptic neurexins that form ciscomplexes with neuroligins, but not of mutant neurexins unable to bind to neuroligins. Our data uncover a cis/trans-protein interaction network as a general design principle that organizes reciprocal dendro dendritic synapses by compartmentalizing neurexin-based trans-synaptic protein complexes.

Improvisation: A novel tool to study musicality

Humans spontaneously invent songs from an early age. Here, we exploit this natural inclination to probe implicit musical knowledge in 33 untrained and poor singers (amusia). Each sang 28 long improvisations as a response to a verbal prompt or a continuation of a melodic stem. To assess the extent to which each improvisation reflects tonality, a core organizational principle of musicality, we developed a new algorithm that compares a sung excerpt to a probability density function representing the tonal hierarchy of Western music. The results show signatures of tonality in both nonmusicians and individuals with congenital amusia, who have notorious difficulty performing musical tasks that require explicit responses and memory. The findings are a proof of concept that improvisation can serve as a novel, even enjoyable method for systematically measuring hidden aspects of musicality across the spectrum of musical ability.

Reading the Masoretic Psalter as a Book: Editorial Trends and Redactional Trajectories

The publication of Gerald H. Wilson’s The Editing of the Hebrew Psalter in 1985 marked a distinct shift in approaches to Psalms research. This article reviews this shift from psalm to Psalter exegesis. North American scholarship tends to follow a synchronic approach and to describe the shape of the Psalter. German scholarship tends to use a diachronic perspective and trace the shaping of the Psalter to explain how it attained its final form. There are growing signs of dialogue and convergence between these two main approaches to the editing of the Hebrew Psalter, which overshadow form-critical and liturgical approaches to the editing of the Psalter. Adherents of the shape and the shaping approach tend to propose a specific theme, organizational principle, or redactional intent to explain the Psalter’s final form. The multi-faceted nature of the Psalter and its long and complex history imply that, in spite of a multitude of publications, the last word on editorial trends and redactional trajectories has not been spoken.

Asymmetric thinning of the cerebral cortex across the adult lifespan is accelerated in Alzheimer’s disease

Aging and Alzheimer’s disease (AD) are associated with progressive brain disorganization. Although structural asymmetry is an organizing feature of the cerebral cortex it is unknown whether continuous age- and AD-related cortical degradation alters cortical asymmetry. Here, in multiple longitudinal adult lifespan cohorts we show that higher-order cortical regions exhibiting pronounced asymmetry at age ~20 also show progressive asymmetry-loss across the adult lifespan. Hence, accelerated thinning of the (previously) thicker homotopic hemisphere is a feature of aging. This organizational principle showed high consistency across cohorts in the Lifebrain consortium, and both the topological patterns and temporal dynamics of asymmetry-loss were markedly similar across replicating samples. Asymmetry-change was further accelerated in AD. Results suggest a system-wide dedifferentiation of the adaptive asymmetric organization of heteromodal cortex in aging and AD.