Frequency-dependent Changes Research Articles

Soliton dynamics in an all-normal-dispersion photonic crystal fiber with frequency-dependent Kerr nonlinearity

We explore high-order soliton evolution in a composite all-normal dispersion photonic crystal fiber with frequency-dependent doping nonlinearity that can vary from positive to negative and vanish at a specific wavelength, named the zero-nonlinearity wavelength (ZNW). The change in frequency dependence of doping nonlinearity dramatically adjusts the position of the ZNW and the nonlinear strength acting on the supercontinuum spectral component. As the negative (positive) frequency dependence decreases (increases), one of two generated fundamental solitons via the combined action of negative nonlinearity and normal dispersion first has a gradually boosting soliton self-frequency shift (SSFS), and then a more suppressed SSFS, but is finally limited within an increasingly small spectral range while the other has a gradually decreasing SSFS toward the ZNW and radiates a broader and stronger phase-matched dispersive wave (DW) in the nonsolitonic region. Note that the collision between two fundamental solitons plays a significant role in regulating their temporal and spectral shift as well as energy redistribution. Furthermore, the numeric sign of the frequency dependence of doping nonlinearity provides another potential tool in controlling the spectral shift direction of fundamental solitons and DWs.

Nanoscale Spin Injector Driven by a Microwave Voltage

We propose an electrically driven spin injector into normal metals and semiconductors, which is based on a magnetic tunnel junction (MTJ) subjected to a microwave voltage. Efficient functioning of such an injector is provided by electrically induced magnetization precession in the "free" layer of MTJ, which generates the spin pumping into a metallic or semiconducting overlayer. We theoretically describe the spin and charge dynamics in the CoFeB/MgO/CoFeB/Au(GaAs) heterostructures. First, the magnedynamics in the free CoFeB layer is quantified with the account of a spin-transfer torque and a voltage-controlled magnetic anisotropy. By numerically solving the magnetodynamics equation, we determine dependences of the precession amplitude on the frequency $f$ and magnitude $V_\mathrm{max}$ of the ac voltage applied to the MTJ. It is found that the frequency dependence changes drastically above the threshold amplitude $V_\mathrm{max} \approx 200$mV, exhibiting a break at the resonance frequency $f_\mathrm{res}$ due to nonlinear effects. The results obtained for the magnetization dynamics are used to describe the spin injection and pumping into the Au and GaAs overlayers. Since the generated spin current creates additional charge current owing to the inverse spin Hall effect, we also calculate distribution of the electric potential in the thick Au overlayer. The calculations show that the arising transverse voltage becomes experimentally measurable at $f = f_\mathrm{res}$. Finally, we evaluate the spin accumulation in a long n$^+$-GaAs bar coupled to the MTJ and determine its temporal variation and spatial distribution along the bar. It is found that the spin accumulation under resonant excitation is large enough for experimental detection even at micrometer distances from the MTJ. This result demonstrates high efficiency of the described nanoscale spin injector.

Frequency-Dependent Changes in Interhemispheric Functional Connectivity Measured by Resting-State fMRI in Children With Idiopathic Generalized Epilepsy.

Epilepsy is associated with abnormal spatiotemporal changes in resting-state brain connectivity, but how these changes are characterized in interhemispheric coupling remains unclear. This study aimed to characterize frequency-dependent alterations in voxel-wise mirrored homotopic connectivity (VMHC) measured by resting-state functional magnetic resonance imaging (rs-fMRI) in children with idiopathic generalized epilepsy (IGE). Rs-fMRI data were collected in 21 children with IGE and 22 demographically matched children with typical development. We used three resting-state frequency bands (full, 0.01–0.08 Hz; slow-4, 0.027–0.073 Hz; slow-5, 0.01–0.027 Hz) to compute VMHC and locate the significant foci. Voxel-wise p <0.001 and cluster-level p <0.05 cluster-level family-wise error correction was applied. In between-group comparisons, we identified that the full and higher frequency (slow-4) bands showed similar reductions in VMHC including Rolandic operculum, putamen, superior frontal, lateral parietal, middle cingulate, and precuneus in children with IGE. In the lower frequency band (slow-5), we identified specific reductions in VMHC in orbitofrontal and middle temporal gyri in children with IGE. Further analyses on main effects and interaction between group and frequency band suggested significant frequency-dependent changes in VMHC, and no significant interaction was found. The results were generally similar with global brain signal regression. Additional association analysis showed that VMHC in the putamen within the full and slow-4 bands was significantly positively correlated with chronological age in children with IGE, and the same analysis was non-significant in the controls; VMHC in the medial prefrontal region in the slow-4 band was significantly positively correlated with IQ performance sub-score. Our findings suggest that IGE children show frequency-dependent changes in interhemispheric integration that spans regions and systems involving cortical-subcortical, language, and visuomotor processing. Decreased functional coupling within the dorsal striatum may reflect atypical development in children with IGE.

Cellulose-Multiwall Carbon Nanotube Fiber Actuator Behavior in Aqueous and Organic Electrolyte.

As both consumers and producers are shifting from fossil-derived materials to other, more sustainable approaches, there is a growing interest in bio-origin and biodegradable polymers. In search of bio-degradable electro-mechanically active materials, cellulose-multi wall carbon nanotube (Cell-CNT) composites are a focus for the development of actuators and sensors. In the current study, our aim was to fabricate Cell-CNT composite fibers and study their electro-mechanical response as linear actuators in aqueous and propylene carbonate-based electrolyte solutions. While the response was (expectedly) strongly solvent dependent, the different solvents also revealed unexpected phenomena. Cell-CNT fibers in propylene carbonate revealed a strong back-relaxation process at low frequencies, and also a frequency dependent response direction change (change of actuation direction). Cell-CNT fibers operated in aqueous electrolyte showed response typical to electrochemical capacitors including expansion at discharging with controllable actuation dependence on charge density. While the response was similarly stable in both electrolyte solution systems, the aqueous electrolytes were clearly favorable for Cell-CNT with 3.4 times higher conductivities, 4.3 times higher charge densities and 11 times higher strain.

Multifrequency Dynamics of Cortical Neuromagnetic Activity Underlying Seizure Termination in Absence Epilepsy.

PurposeThis study aimed to investigate the spectral and spatial signatures of neuromagnetic activity underlying the termination of absence seizures.MethodsMagnetoencephalography (MEG) data were recorded from 18 drug-naive patients with childhood absence epilepsy (CAE). Accumulated source imaging (ASI) was used to analyze MEG data at the source level in seven frequency ranges: delta (1–4 Hz), theta (4–8 Hz), alpha (8–12 Hz), beta (12–30 Hz), gamma (30–80 Hz), ripple (80–250 Hz), and fast ripple (250–500 Hz).ResultIn the 1–4, 4–8, and 8–12 Hz ranges, the magnetic source during seizure termination appeared to be consistent over the ictal period and was mainly localized in the frontal cortex (FC) and parieto-occipito-temporal junction (POT). In the 12–30 and 30–80 Hz ranges, a significant reduction in source activity was observed in the frontal lobe during seizure termination as well as a decrease in peak source strength. The ictal peak source strength in the 1–4 Hz range was negatively correlated with the ictal duration of the seizure, whereas in the 30–80 Hz range, it was positively correlated with the course of epilepsy.ConclusionThe termination of absence seizures is associated with a dynamic neuromagnetic process. Frequency-dependent changes in the FC were observed during seizure termination, which may be involved in the process of neural network interaction. Neuromagnetic activity in different frequency bands may play different roles in the pathophysiological mechanism during absence seizures.

Brain-like spatiotemporal information processing with nanosized second-order synaptic emulators; “solid-state memory visualizer”

Abstract Emulating bio-counterpart artificial intelligence abilities at the hardware level requires high-density integration of artificial synapses. For that, not only nanosize artificial synapses with reliable multilevel functionality is needed but visualization of critical information processing within it is also essential. Here, we demonstrate nanosize second-order synaptic emulator and observed the dynamics of neuromorphic spatiotemporal information processing using local probe force microscopy. Particularly, the device shows stable analog hysteresis loop opening and multilevel memory storage, which was confirmed by current mapping. All versatile and necessary synaptic features like shot-, long-term memory, and corresponding dynamics, long term potentiation, and depression and pulse pair facilitation are demonstrated. Further, both Bienenstock, Cooper, and Munro learning rules e.g., frequency-dependent synaptic weight change and sliding threshold characteristics ‒ spike rate-dependent plasticity are confirmed. Based on Kelvin probe force microscopy measurements, the observed results are quantitatively explained as a dynamic of charge trapping/detrapping. Benefited from high-density integration and multilevel data storage along with processing, our approach exhibit an attractive future to build advance neuromorphic circuits at nanoscale.

Frequency- and state-dependent effects of hippocampal neural disinhibition on hippocampal local field potential oscillations in anesthetized rats.

Reduced inhibitory GABA function, so-called neural disinhibition, has been implicated in cognitive disorders, including schizophrenia and age-related cognitive decline. We previously showed in rats that hippocampal disinhibition by local microinfusion of the GABA-A receptor antagonist picrotoxin disrupted memory and attention and enhanced hippocampal multi-unit burst firing recorded around the infusion site under isoflurane anesthesia. Here, we analyzed the hippocampal local field potential (LFP) recorded alongside the multi-unit data. We predicted frequency-specific LFP changes, based on previous studies implicating GABA in hippocampal oscillations, with the weight of evidence suggesting that disinhibition would facilitate theta and disrupt gamma oscillations. Using a new semi-automated method based on the kurtosis of the LFP peak-amplitude distribution as well as on amplitude envelope thresholding, we separated three distinct hippocampal LFP states under isoflurane anesthesia: "burst" and "suppression" states-high-amplitude LFP spike bursts and the interspersed low-amplitudeperiods-and a medium-amplitude "continuous" state. The burst state showed greater overall power than suppression and continuous states and higher relative delta/theta power, but lower relative beta/gamma power. The burst state also showed reduced functional connectivity across the hippocampal recording area, especially around theta and beta frequencies. Overall neuronal firing was higher in the burst than the other two states, whereas the proportion of burst firing was higher in burst and continuous states than the suppression state. Disinhibition caused state- and frequency-dependent LFP changes, tending to increase power at lower frequencies (<20 Hz), but to decrease power and connectivity at higher frequencies (>20 Hz) in burst and suppression states. The disinhibition-induced enhancement of multi-unit bursting was also state-dependent, tending to be more pronounced in burst and suppression states than the continuous state. Overall, we characterized three distinct hippocampal LFP states in isoflurane-anesthetized rats. Disinhibition changed hippocampal LFP oscillations in a state- and frequency-dependent way. Moreover, the disinhibition-induced enhancement of multi-unit bursting was also LFP state-dependent.

Galerkin Boundary Element Methods for High-Frequency Multiple-Scattering Problems

We consider high-frequency multiple-scattering problems in the exterior of two-dimensional smooth scatterers consisting of finitely many compact, disjoint, and strictly convex obstacles. To deal with this problem, we propose Galerkin boundary element methods, namely the frequency-adapted Galerkin boundary element methods and Galerkin boundary element methods generated using frequency-dependent changes of variables. For both of these new algorithms, in connection with each multiple-scattering iterate, we show that the number of degrees of freedom needs to increase as $$\mathcal {O}(k^{\epsilon })$$ (for any $$\epsilon >0$$) with increasing wavenumber k to attain frequency-independent error tolerances. We support our theoretical developments by a variety of numerical implementations.

Resting state fMRI reveals differential effects of glucose administration on central appetite signalling in young and old adults.

Healthy aging has been associated with reduced appetite and lower energy intake, which can lead to loss of bodyweight, undernutrition and related health problems. The causes for the decline in caloric intake are multifactorial, involving physiological and non-physiological processes. Here we examined the effect of glucose on brain function in healthy adults as well as age-related, physiological changes in brain responses associated with macronutrient intake. Using a randomized, double-blind, balanced cross-over design, younger (n = 16, aged 21-30) and older (n = 16, aged 55-78) adults received a drink containing glucose and a taste-matched placebo after an overnight fast. Blood glucose and hunger were assessed at baseline and 20 min post-ingestion, after which participants underwent resting state functional magnetic resonance imaging. Frequency-dependent changes associated with glucose administration in slow-5 (0.01-0.027 Hz) and slow-4 (0.027-0.073 Hz) amplitude of low-frequency fluctuations (ALFF) and fractional ALFF (fALFF) of the blood oxygen level-dependent (BOLD) signal were investigated within the young healthy adults, and then extended to the older age group. Consistent with previous reports, glucose decreased amplitude in slow-5 fALFF within the left orbitofrontal cortex and insular cortex in the young adults. We observed a significant interaction in slow-5 ALFF and fALFF in the left insula, such that younger participants showed a decrease in BOLD amplitude, whereas older participants showed an increase, after glucose administration. We further observed an interaction in slow-4 ALFF in the occipital region and precuneus, with older participants showing an increase in magnitude of slow-4 ALFF and younger participants showing a decrease in the same measure. These age-related, frequency-dependent changes in the magnitude of the BOLD signal in the insula, a key region related to energy homeostasis following feeding, may point to a change in satiety or homeostatic signalling contributing to behavioural changes in energy intake during senescence.

Frequency-dependent changes in mitochondrial number and generation of reactive oxygen species in a rat model of vibration-induced injury

ABSTRACTRegular use of vibrating hand tools results in cold-induced vasoconstriction, finger blanching, and a reduction in tactile sensitivity and manual dexterity. Depending upon the length and frequency, vibration induces regeneration, or dysfunction and apoptosis, inflammation and an increase in reactive oxygen species (ROS) levels. These changes may be associated with mitochondria, this study examined the effects of vibration on total and functional mitochondria number. Male rats were exposed to restraint or tail vibration at 62.5, 125, or 250 Hz. The frequency-dependent effects of vibration on mitochondrial number and generation of oxidative stress were examined. After 10 days of exposure at 125 Hz, ventral tail arteries (VTA) were constricted and there was an increase in mitochondrial number and intensity of ROS staining. In the skin, the influence of vibration on arterioles displayed a similar but insignificant response in VTA. There was also a reduction in the number of small nerves with exposure to vibration at 250 Hz, and a reduction in mitochondrial number in nerves in restrained and all vibrated conditions. There was a significant rise in the size of the sensory receptors with vibration at 125 Hz, and an elevation in ROS levels. Based upon these results, mitochondria number and activity are affected by vibration, especially at frequencies at or near resonance. The influence of vibration on the vascular system may either be adaptive or maladaptive. However, the effects on cutaneous nerves might be a precursor to loss of innervation and sensory function noted in workers exposed to vibration.

АЛГОРИТМ ОЦЕНКИ И КОРРЕКЦИИ ПАРАМЕТРОВ МНОГОЛУЧЕВОГО КАНАЛА ПРИ ДЕМОДУЛЯЦИИ СИГНАЛОВ OFDM

OFDM signals form the basis of the radio interface of 4G mobile networks. Among the most well-known systems using OFDM signals, the LTE / LTE-Advanced, IEEE 802.11, IEEE 802.16 family, as well as DVB-T, DVB-T2 digital television standards, should be noted. Due to the high spectral efficiency and noise immunity in channels with multipath propagation of radio waves, OFDM signals are also used in other systems under development. Radio systems with OFDM signals have two significant drawbacks: the high peak factor (PAPR), which reduces the efficiency of the radio transmitter, and the high sensitivity of the demodulator to frequency synchronization errors. Because of them, in the LTE system in the Up lines (from a subscriber - mobile station – MS - to the base station - BS), the SC-OFDM transmission method is used instead of the classical OFDM, which reduces the spectral efficiency. High-speed user movement in an environment with many diffusers characteristic of dense urban development leads to frequency dispersion, when a Doppler spectrum occurs near each subcarrier of the OFDM signal. In addition, in any radio communication system, there are random fluctuations in the phase of the radio signal caused by the instability of the generators of the radio receiver and radio transmitter. As a result, the orthogonality of the subcarriers is violated and mutual interference between them (ICI - inter-carrier interference) occurs. This can significantly impair the noise immunity of the transmission system. Therefore, an integral part of the demodulator processing the OFDM signal is the channel parameter estimation and correction unit (adaptive equalizer). There are two categories of equalizers that determine the parameters of the channel – in the frequency domain and in the time domain. Since the OFDM signal demodulators use the fast Fourier transform at the subcarrier separation stage, as well as the pilot subcarriers being contained in the signal structure, it is advisable to consider equalizers that calculate the channel parameters in the frequency domain for efficient hardware implementation and good performance. Such an equalizer joins in with a demodulator after the stage of fast Fourier transformation. Traditionally for OFDM signals, an adaptive equalizer is built based on approximation of frequency description of channel by averaging of results obtained on the pilot subcarrier. Frequency dependence of total phase change of multibeam signal is not considered in such methods. Accordingly, good results can be expected at the dense location of the pilot subcarrier that reduces frequency efficiency in turn. An offered method allows considering a frequency-dependent phase change and interference losses, arising due to addition of copies of the signal from the different ways of distribution. It is special topically in systems with a small number of the pilot subcarriers.

ICE CRYSTAL DYNAMICS IN THE NANOCOMPOSITE NETWORKS

Water is abundant in every day's life and critically useful in many biological systems and in water-based mechanical devices. Freeze-thaw process is one of the inevitable dynamics especially for the materials working at sub-zero conditions where ice crystal changes the physical property of the whole crystal-embedded composite systems. However, still many phenomena have not been explained in terms of crystal control methodology in conjunction with mechanical properties. In this study, ice crystal dynamics occurring in network systems has been discussed. Small size of network structure contributes to crystal growth inhibition especially time-dependent recrystallization. This could be explained by nano-scale confinement effect at the initial nucleation/growth stage, controlling size and shape of ice crystallites. The physical property of crystal embedded-nanocomposite is dominated by ice crystal behaviors over the network. This includes freezing point depression, frequency-dependent and temperature-dependent storage modulus changes and cooling rate- dependent dynamics. This study sheds light on ice crystal control methodology which would be useful in various materials and machines working under freeze-thaw dynamics.

Pinna-related transfer functions and lossless wave equation using finite-difference methods: Verification and asymptotic solution.

A common approach when employing discrete mathematical models is to assess the reliability and credibility of the computation of interest through a process known as solution verification. Present-day computed head-related transfer functions (HRTFs) seem to lack robust and reliable assessments of the numerical errors embedded in the results which makes validation of wave-based models difficult. This process requires a good understanding of the involved sources of error which are systematically reviewed here. The current work aims to quantify the pinna-related high-frequency computational errors in the context of HRTFs and wave-based simulations with finite-difference models. As a prerequisite for solution verification, code verification assesses the reliability of the proposed implementation. In this paper, known and manufactured formal solutions are used and tailored for the wave equation and frequency-independent boundary conditions inside a rectangular room of uniform acoustic wall-impedance. Asymptotic estimates for pinna acoustics are predicted in the frequency domain based on regression models and a convergence study on sub-millimeter grids. Results show an increasing uncertainty with frequency and a significant frequency-dependent change among computations on different grids.

Investigation on frequency-dependent hysteresis loops of ferroelectric materials

In this paper, a frequency-dependent theory is developed to study the polarization hysteresis loops of ferroelectric materials. From experimental observations, the polarization hysteresis loops strongly depend on the electric field loading frequency. When the frequency increases both remanent polarization and coercive electric field are increasing, while the dielectric constant remains unchanged at the given range of the frequency. An exponential function is introduced to express such frequency-dependent changes of the remanent polarization and the coercive field. Then a micromechanics-based approach can be applied to study hysteresis loops of ferroelectrics. To verify the developed theory, we first compare the results between the theoretical calculations and experimental data of PZT. Then we applied the model to study the frequency effects on hysteresis loops of a complex ceramic BaMn3Ti4O14.25 (BMT-134) under the electric field.

The dielectric properties and electrical conductivity of LDPE modified by fillers of biological origin

In this work, were investigated about the investigation of the frequency-dependent change in the character of the dielectric permeability and the tangent of dielectric loss angles of the biocomposites type LDPE + x vol.% FB obtained by fish bone fillers adding to the matrix of low density polyethylene and the bionanocomposites type LDPE + x vol.% FB + 1 vol.% Al with adding to this mixture 1 vol.% aluminum nanoparticles size 50 nm, calculation the actual and imaginary parts of the dielectric permeability of these materials, and the investigation of frequency change of electrical conductivity of both bio and bionanocomposites. It has been established that the dielectric permeability of biocomposites practically does not change in the frequency range 0–103 kHz.

Evaluation of linear and non-linear activation dynamics models for insect muscle.

In computational modelling of sensory-motor control, the dynamics of muscle contraction is an important determinant of movement timing and joint stiffness. This is particularly so in animals with many slow muscles, as is the case in insects—many of which are important models for sensory-motor control. A muscle model is generally used to transform motoneuronal input into muscle force. Although standard models exist for vertebrate muscle innervated by many motoneurons, there is no agreement on a parametric model for single motoneuron stimulation of invertebrate muscle. Although several different models have been proposed, they have never been evaluated using a common experimental data set. We evaluate five models for isometric force production of a well-studied model system: the locust hind leg tibial extensor muscle. The response of this muscle to motoneuron spikes is best modelled as a non-linear low-pass system. Linear first-order models can approximate isometric force time courses well at high spike rates, but they cannot account for appropriate force time courses at low spike rates. A linear third-order model performs better, but only non-linear models can account for frequency-dependent change of decay time and force potentiation at intermediate stimulus frequencies. Some of the differences among published models are due to differences among experimental data sets. We developed a comprehensive toolbox for modelling muscle activation dynamics, and optimised model parameters using one data set. The “Hatze-Zakotnik model” that emphasizes an accurate single-twitch time course and uses frequency-dependent modulation of the twitch for force potentiation performs best for the slow motoneuron. Frequency-dependent modulation of a single twitch works less well for the fast motoneuron. The non-linear “Wilson” model that optimises parameters to all data set parts simultaneously performs better here. Our open-access toolbox provides powerful tools for researchers to fit appropriate models to a range of insect muscles.

Frequency-dependent changes in fractional amplitude of low-frequency oscillations in Alzheimer's disease: a resting-state fMRI study.

Alzheimer's disease (AD) is the most common neurodegenerative disease in elderly individuals. We conducted this study to examine whether alterations in the fractional amplitudes of low-frequency fluctuations (fALFF) in the AD spectrum were frequency-dependent and symptom-relevant. A total of 43 patients with subjective cognitive decline (SCD), 52 with amnestic mild cognitive impairment (aMCI), 44 with Alzheimer's dementia (d-AD) and 55 well-matched controls participated in resting-state functional magnetic resonance imaging (rs-fMRI) scans. The amplitudes were measured using fALFF within the slow-4 (0.027-0.073Hz) and slow-5 (0.01-0.027Hz) bands. Repeated-measures analysis of variance was performed on fALFF within two bands and correlated with neuropsychological test scores. The significant main effects of frequency and group on fALFF differed widely across brain regions. There were more varied areas in the slow-5 band than the slow-4 band. The fALFF associated with primary disease effects was mainly distributed in the parietal lobe. Obvious frequency band and group interaction effects were observed in the left angular gyrus, left calcarine fissure and surrounding cortex, left superior cerebellum, left cuneus and right lingual gyrus. Neuropsychological tests scores were significantly correlated with the fALFF magnitude of the left cuneus and right lingual in the slow-5 band. Our results suggested that the AD continuum had abnormal amplitudes in intrinsic brain activity, and these abnormalities were frequency-dependent and mainly associated with the slow-5 band rather than the slow-4 band. This may guide the frequency choice of future rs-fMRI studies and provide new insights into the neuropathophysiology of AD.

Short-term dynamics of input and output of CA1 network greatly differ between the dorsal and ventral rat hippocampus

BackgroundThe functional heterogeneity of the hippocampus along its longitudinal axis at the level of behavior is an established concept; however, the neurobiological mechanisms are still unknown. Diversifications in the functioning of intrinsic hippocampal circuitry including short-term dynamics of synaptic inputs and neuronal output, that are important determinants of information processing in the brain, may profoundly contribute to functional specializations along the hippocampus. The objectives of the present study were the examination of the role of the GABAA receptor-mediated inhibition, the μ-opioid receptors and the effect of stimulation intensity on the dynamics of both synaptic input and neuronal output of CA1 region in the dorsal and ventral hippocampus. We used recordings of field potentials from adult rat hippocampal slices evoked by brief repetitive activation of Schaffer collaterals.ResultsWe find that the local CA1 circuit of the dorsal hippocampus presents a remarkably increased dynamic range of frequency-dependent short-term changes in both input and output, ranging from strong facilitation to intense depression at low and high stimulation frequencies respectively. Furthermore, the input–output relationship in the dorsal CA1 circuit is profoundly influenced by frequency and time of presynaptic activation. Strikingly, the ventral hippocampus responds mostly with depression, displaying a rather monotonous input–output relationship over frequency and time. Partial blockade of GABAA receptor-mediated transmission (by 5 μM picrotoxin) profoundly influences input and output dynamics in the dorsal hippocampus but affected only the neuronal output in the ventral hippocampus. M-opioid receptors control short-term dynamics of input and output in the dorsal hippocampus but they play no role in the ventral hippocampus.ConclusionThe results demonstrate that information processing by CA1 local network is highly diversified between the dorsal and ventral hippocampus. Transient detection of incoming patterns of activity and frequency-dependent sustained signaling of amplified neuronal information may be assigned to the ventral and dorsal hippocampal circuitry respectively. This disparity should have profound implications for the functional roles ascribed to distinct segments along the long axis of the hippocampus.

Thermal dielectroscopy study on the vertical and horizontal interactions in erythrocyte sub-membrane skeleton

Thermal dielectroscopy was used to study the spectrin-based sub-membrane skeleton (MS) and its attachment to the lipid bilayer of human erythrocyte membrane. At the spectrin denaturation temperature, TA, the complex impedance, Z*, and capacitance, C*, sustain sigmoid, frequency-dependent changes, ΔZ* = ΔZ' + jΔZ" and ΔC* = ΔC' - jΔC", respectively. The impedance change plot, -ΔZ" vs. ΔZ′, depicts two semicircles revealing two dielectric relaxations on MS, here designated as beta and gamma relaxations on MS [Ivanov and Paarvanova, 2016]. We report here that ortho-vanadate (5 mM), alkaline cytosole (pH 9.2), N-ethylmaleimide (5 mM), diamide (1 mM) and cell shrinkage, all known to disrupt the band 3 tetramer-spectrin attachment site, inhibited gamma relaxation, which represents the direct interaction of high frequency field with spectrin. By contrast DNAase I, diphosphoglycerate (10 mM) and urea (1–2 M), all known to disrupt the actin-spectrin junction, inhibited beta relaxation, which represents the piezo effect on spectrin, powered by the low frequency electrostriction of lipid bilayer. The frequency curves of ΔCd" (dielectric component of ΔC") and of ΔC′ both determined the critical frequencies of beta and gamma relaxations as 1.4 and 6 MHz at 46 °C (1.1 and 4.5 MHz at 37 °C), respectively. Based on the presented results, the effect of MS attachment on the dynamics and elasticity of MS was discussed.

Frequency-Dependent Changes in Resting State Electroencephalogram Functional Networks after Traumatic Brain Injury in Piglets.

Traumatic brain injury (TBI) is a major health concern in children, as it can cause chronic cognitive and behavioral deficits. The lack of objective involuntary metrics for the diagnosis of TBI makes prognosis more challenging, especially in the pediatric context, in which children are often unable to articulate their symptoms. Resting state electroencephalograms (EEG), which are inexpensive and non-invasive, and do not require subjects to perform cognitive tasks, have not yet been used to create functional brain networks in relation to TBI in children or non-human animals; here we report the first such study. We recorded resting state EEG in awake piglets before and after TBI, from which we generated EEG functional networks from the alpha (8-12 Hz), beta (16.5-25 Hz), broad (1-35 Hz), delta (1-3.5 Hz), gamma (30-35 Hz), sigma (13-16 Hz), and theta (4-7.5 Hz) frequency bands. We hypothesize that mild TBI will induce persistent frequency-dependent changes in the 4-week-old piglet at acute and chronic time points. Hyperconnectivity was found in several frequency band networks after TBI. This study serves as proof of concept that the study of EEG functional networks in awake piglets may be useful for the development of diagnostic metrics for TBI in children.