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neural dynamics

Minoru Koyama, Avinash Pujala
A series of classical studies in non-human primates has revealed the neuronal activity patterns underlying decision-making. However, the circuit mechanisms for such patterns remain largely unknown. Recent detailed circuit analyses in simpler neural systems have started to reveal the connectivity patterns underlying analogous processes. Here we review a few of these systems that share a particular connectivity pattern, namely mutual inhibition of lateral inhibition. Close examination of these systems suggests that this recurring connectivity pattern ('network motif') is a building block to enforce particular dynamics, which can be used not only for simple behavioral choice but also for more complex choices and other brain functions...
January 16, 2018: Current Opinion in Neurobiology
Zimbul Albo, Johannes Gräff
Long-lasting memories form the basis of our identity as individuals and lie central in shaping future behaviours that guide survival. Surprisingly, however, our current knowledge of how such memories are stored in the brain and retrieved, as well as the dynamics of the circuits involved, remains scarce despite seminal technical and experimental breakthroughs in recent years. Traditionally, it has been proposed that, over time, information initially learnt in the hippocampus is stored in distributed cortical networks...
March 19, 2018: Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences
Martin Goethe, Jan Gleixner, Ignacio Fita, J Miguel Rubi
A knowledge-based method for configurational entropy prediction of proteins is presented which is extremely fast compared to previous approaches because it does not involve any kind of configurational sampling. Instead, the configurational entropy of a query fold is estimated by evaluating an artificial neural network which was trained on molecular-dynamics simulations of about 1000 proteins. The predicted entropy can be incorporated into a large class of protein software based on cost-function minimization/evaluation in which configurational entropy is currently neglected for performance reasons...
January 19, 2018: Journal of Chemical Theory and Computation
Vincent Prevot, Bénédicte Dehouck, Ariane Sharif, Philippe Ciofi, Paolo Giacobini, Jerome Clasadonte
The fertility and survival of an individual rely on the ability of the periphery to promptly, effectively and reproducibly communicate with brain neural networks that control reproduction, food intake and energy homeostasis. Tanycytes, a specialized glial cell type lining the wall of the third ventricle in the median eminence of the hypothalamus, appear to act as the linchpin of these processes by dynamically controlling the secretion of neuropeptides into the portal vasculature by hypothalamic neurons and regulating blood-brain and blood-cerebrospinal fluid exchanges, both processes that depend on the ability of these cells to adapt their morphology to the physiological state of the individual...
January 17, 2018: Endocrine Reviews
Zabit Hameed, Saqib Saleem, Jawad Mirza, Muhammad Salman Mustafa, Qamar-Ul-Islam
Epilepsy is a brain disorder characterised by the recurrent and unpredictable interruptions of normal brain function, called epileptic seizures. The present study attempts to derive new diagnostic indices which may delineate between ictal and interictal states of epilepsy. To achieve this, the nonlinear modeling approach of global principal dynamic modes (PDMs) is adopted to examine the functional connectivity of the temporal and frontal lobes with the occipital brain segment using an ensemble of paediatric EEGs having the presence of epileptic seizure...
2018: PloS One
Tobias Zimmermann, Bertram Taetz, Gabriele Bleser
Human body motion analysis based on wearable inertial measurement units (IMUs) receives a lot of attention from both the research community and the and industrial community. This is due to the significant role in, for instance, mobile health systems, sports and human computer interaction. In sensor based activity recognition, one of the major issues for obtaining reliable results is the sensor placement/assignment on the body. For inertial motion capture (joint kinematics estimation) and analysis, the IMU-to-segment (I2S) assignment and alignment are central issues to obtain biomechanical joint angles...
January 19, 2018: Sensors
Frigyes Samuel Racz, Peter Mukli, Zoltan Nagy, Andras Eke
Brain function is organized as a network of functional connections between different neuronal populations with connection strengths dynamically changing in time and space. Studies investigating functional connectivity (FC) usually follow a static approach when describing FC by considering the connectivity strengths constant, however a dynamic approach seems more reasonable, as this way the spatio-temporal dynamics of the underlying system can also be captured. Objective: The scale-free, i.e. fractal nature of neural dynamics is an inherent property of the nervous system...
January 19, 2018: Physiological Measurement
Audrey J Sederberg, Jason N MacLean, Stephanie E Palmer
To compensate for sensory processing delays, the visual system must make predictions to ensure timely and appropriate behaviors. Recent work has found predictive information about the stimulus in neural populations early in vision processing, starting in the retina. However, to utilize this information, cells downstream must be able to read out the predictive information from the spiking activity of retinal ganglion cells. Here we investigate whether a downstream cell could learn efficient encoding of predictive information in its inputs from the correlations in the inputs themselves, in the absence of other instructive signals...
January 18, 2018: Proceedings of the National Academy of Sciences of the United States of America
Clarissa Martinez-Rubio, Angelique C Paulk, Eric J McDonald, Alik S Widge, Emad N Eskandar
Associative learning is crucial for daily function, involving a complex network of brain regions. One region, the nucleus basalis of Meynert (NBM), is a highly interconnected, largely cholinergic structure implicated in multiple aspects of learning. We show that single neurons in the NBM of non-human primates (NHPs; N=2 males; Macaca mulatta) encode learning a new association through spike rate modulation. Yet, the power of low-frequency local field potential (LFP) oscillations decreases in response to novel, not-yet-learned stimuli but then increase as learning progresses...
January 18, 2018: Journal of Neuroscience: the Official Journal of the Society for Neuroscience
R Pasion, C Fernandes, A R Gonçalves, F Ferreira-Santos, R Páscoa, F Barbosa, J Marques-Teixeira
Despite the accumulated knowledge on moral decision-making in the early stages of development, empirical evidence is still limited in the old-aged adults. The current study contributes to unveil the neural correlates of judgments of moral transgressions as a function of aging, by examining the temporal dynamics of neural activation elicited by intentional and accidental harmful actions in three groups of healthy participants: young adults (18-35), adults (40-55), and older adults (60-75). Older adults were slower and less accurate in rating intentionality, compared to the younger groups...
January 18, 2018: Social Neuroscience
Jose M Esnaola-Acebes, Alex Roxin, Daniele Avitabile, Ernest Montbrió
We investigate the modes of oscillation of heterogeneous ring networks of quadratic integrate-and-fire (QIF) neurons with nonlocal, space-dependent coupling. Perturbations of the equilibrium state with a particular wave number produce transient standing waves with a specific temporal frequency, analogously to those in a tense string. In the neuronal network, the equilibrium corresponds to a spatially homogeneous, asynchronous state. Perturbations of this state excite the network's oscillatory modes, which reflect the interplay of episodes of synchronous spiking with the excitatory-inhibitory spatial interactions...
November 2017: Physical Review. E
N Roy, P Sanz-Leon, P A Robinson
The modulation of neural quantities by presynaptic and postsynaptic activities via local feedback processes is investigated by incorporating nonlinear phenomena such as relative refractory period, synaptic enhancement, synaptic depression, and habituation. This is done by introducing susceptibilities, which quantify the response in either firing threshold or synaptic strength to unit change in either presynaptic or postsynaptic activity. Effects on the power spectra are then analyzed for a realistic corticothalamic model to determine the spectral signatures of various nonlinear processes and to what extent these are distinct...
November 2017: Physical Review. E
K N Mukta, J N MacLaurin, P A Robinson
Corticothalamic neural field theory is applied to a spherical geometry to better model neural activity in the human brain and is also compared with planar approximations. The frequency power spectrum, correlation, and coherence functions are computed analytically and numerically. The effects of cortical boundary conditions and resulting modal aspects of spherical corticothalamic dynamics are explored, showing that the results of spherical and finite planar geometries converge to those for the infinite planar geometry in the limit of large brain size...
November 2017: Physical Review. E
Sergey Makovkin, Anil Kumar, Alexey Zaikin, Sarika Jalan, Mikhail Ivanchenko
Inspired by the recent interest in collective dynamics of biological neural networks immersed in the glial cell medium, we investigate the frequency and phase order, i.e., Kuramoto type of synchronization in a multiplex two-layer network of phase oscillators of different time scales and topologies. One of them has a long-range connectivity, exemplified by the Erdős-Rényi random network, and supports both kinds of synchrony. The other is a locally coupled two-dimensional lattice that can reach frequency synchronization but lacks phase order...
November 2017: Physical Review. E
Zhuocheng Xiao, Jiwei Zhang, Andrew T Sornborger, Louis Tao
Line attractors in neuronal networks have been suggested to be the basis of many brain functions, such as working memory, oculomotor control, head movement, locomotion, and sensory processing. In this paper, we make the connection between line attractors and pulse gating in feed-forward neuronal networks. In this context, because of their neutral stability along a one-dimensional manifold, line attractors are associated with a time-translational invariance that allows graded information to be propagated from one neuronal population to the next...
November 2017: Physical Review. E
Neta Ravid Tannenbaum, Yoram Burak
We expand the theory of Hawkes processes to the nonstationary case, in which the mutually exciting point processes receive time-dependent inputs. We derive an analytical expression for the time-dependent correlations, which can be applied to networks with arbitrary connectivity, and inputs with arbitrary statistics. The expression shows how the network correlations are determined by the interplay between the network topology, the transfer functions relating units within the network, and the pattern and statistics of the external inputs...
December 2017: Physical Review. E
Zachary P Kilpatrick, Daniel B Poll
Many organisms can remember locations they have previously visited during a search. Visual search experiments have shown exploration is guided away from these locations, reducing redundancies in the search path before finding a hidden target. We develop and analyze a two-layer neural field model that encodes positional information during a search task. A position-encoding layer sustains a bump attractor corresponding to the searching agent's current location, and search is modeled by velocity input that propagates the bump...
December 2017: Physical Review. E
Natasha C Gabay, P A Robinson
Perturbation analysis of neural field theory is used to derive eigenmodes of neural activity on a cortical hemisphere, which have previously been calculated numerically and found to be close analogs of spherical harmonics, despite heavy cortical folding. The present perturbation method treats cortical folding as a first-order perturbation from a spherical geometry. The first nine spatial eigenmodes on a population-averaged cortical hemisphere are derived and compared with previous numerical solutions. These eigenmodes contribute most to brain activity patterns such as those seen in electroencephalography and functional magnetic resonance imaging...
September 2017: Physical Review. E
David Mayett, Nicholas Bitten, Moumita Das, J M Schwarz
Cell migration in morphogenesis and cancer metastasis typically involves interplay between different cell types. We construct and study a minimal, one-dimensional model composed of two different motile cells with each cell represented as an active elastic dimer. The interaction between the two cells via cadherins is modeled as a spring that can rupture beyond a threshold force as it undergoes dynamic loading from the interacting motile cells. We obtain a phase diagram consisting of chase-and-run dynamics and clumping dynamics as a function of the stiffness of the interaction spring and the threshold force and, therefore, posit that active rupture, or rupture via active forces, is a mechanosensitive means to regulate dynamics between cells...
September 2017: Physical Review. E
Rosanna P Sammons, Claudia Clopath, Samuel J Barnes
Persistent synapses are thought to underpin the storage of sensory experience, yet little is known about their structural plasticity in vivo. We investigated how persistent presynaptic structures respond to the loss of primary sensory input. Using in vivo two-photon (2P) imaging, we measured fluctuations in the size of excitatory axonal boutons in L2/3 of adult mouse visual cortex after monocular enucleation. The average size of boutons did not change after deprivation, but the range of bouton sizes was reduced...
January 16, 2018: Cell Reports
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