Motor, somatosensory, and executive cortical areas elicit monosynaptic and polysynaptic neuronal activity in the auditory midbrain

We recently reported that the central nucleus of the inferior colliculus (the auditory midbrain) is innervated by glutamatergic pyramidal cells originating not only in auditory cortex (AC), but also in multiple 'non-auditory' regions of the cerebral cortex. Here, in anaesthetised rats, we used optogenetics and electrical stimulation, combined with recording in the inferior colliculus to determine the functional influence of these descending connections. Specifically, we determined the extent of monosynaptic excitation and the influence of these descending connections on spontaneous activity in the inferior colliculus. A retrograde virus encoding both green fluorescent protein (GFP) and channelrhodopsin (ChR2) injected into the central nucleus of the inferior colliculus (ICc) resulted in GFP expression in discrete groups of cells in multiple areas of the cerebral cortex. Light stimulation of AC and primary motor cortex (M1) caused local activation of cortical neurones and increased the firing rate of neurones in ICc indicating a direct excitatory input from AC and M1 to ICc with a restricted distribution. In naïve animals, electrical stimulation at multiple different sites within M1, secondary motor, somatosensory, and prefrontal cortices increased firing rate in ICc. However, it was notable that stimulation at some adjacent sites failed to influence firing at the recording site in ICc. Responses in ICc comprised singular spikes of constant shape and size which occurred with a short, and fixed latency (∼ 5 ms) consistent with monosynaptic excitation of individual ICc units. Increasing the stimulus current decreased the latency of these spikes, suggesting more rapid depolarization of cortical neurones, and increased the number of (usually adjacent) channels on which a monosynaptic spike was seen, suggesting recruitment of increasing numbers of cortical neurons. Electrical stimulation of cortical regions also evoked longer latency, longer duration increases in firing activity, comprising multiple units with spikes occurring with significant temporal jitter, consistent with polysynaptic excitation. Increasing the stimulus current increased the number of spikes in these polysynaptic responses and increased the number of channels on which the responses were observed, although the magnitude of the responses always diminished away from the most activated channels. Together our findings indicate descending connections from motor, somatosensory and executive cortical regions directly activate small numbers of ICc neurones and that this in turn leads to extensive polysynaptic activation of local circuits within the ICc.

InSpectro-Gadget: A Tool for Estimating Neurotransmitter and Neuromodulator Receptor Distributions for MRS Voxels

Magnetic resonance spectroscopy (MRS) is widely used to estimate concentrations of glutamate and γ -aminobutyric acid (GABA) in specific regions of the living human brain. As cytoarchitectural properties differ across the brain, interpreting these measurements can be assisted by having knowledge of such properties for the MRS region(s) studied. In particular, some knowledge of likely local neurotransmitter receptor patterns can potentially give insights into the mechanistic environment GABA- and glutamatergic neurons are functioning in. This may be of particular utility when comparing two or more regions, given that the receptor populations may differ substantially across them. At the same time, when studying MRS data from multiple participants or timepoints, the homogeneity of the sample becomes relevant, as measurements taken from areas with different cytoarchitecture may be difficult to compare. To provide insights into the likely cytoarchitectural environment of user-defined regions-of-interest, we produced an easy to use tool - InSpectro-Gadget - that interfaces with receptor mRNA expression information from the Allen Human Brain Atlas. This Python tool allows users to input masks and automatically obtain a graphical overview of the receptor population likely to be found within. This includes comparison between multiple masks or participants where relevant. The receptors and receptor subunit genes featured include GABA- and glutamatergic classes, along with a wide range of neuromodulators. The functionality of the tool is explained here and its use is demonstrated through a set of example analyses. The tool is available at https://github.com/lizmcmanus/Inspectro-Gadget .

Converging synaptic and network dysfunctions in distinct autoimmune encephalitis

Psychiatric and neurological symptoms, as well as cognitive deficits, represent a prominent phenotype associated with variable forms of autoimmune encephalitis, regardless of the neurotransmitter receptor targeted by autoantibodies. The mechanistic underpinnings of these shared major neuropsychiatric symptoms remain however unclear. Here, we investigate the impacts of patient-derived monoclonal autoantibodies against the glutamatergic NMDAR (NMDAR mAb) and inhibitory GABAaR (GABAaR mAb) signalling in the hippocampal network. Unexpectedly, both excitatory and inhibitory synaptic receptor membrane dynamics, content and transmissions are altered by NMDAR or GABAaR mAb, irrespective of the affinity or antagonistic effect of the autoantibodies. The effect of NMDAR mAb on inhibitory synapses and GABAaR mAb on excitatory synapses requires neuronal activity and involves protein kinase signalling. At the cell level, both autoantibodies increase the excitation/inhibition balance of principal cell inputs. Furthermore, NMDAR or GABAaR mAb leads to hyperactivation of hippocampal networks through distinct alterations of principal cell and interneuron properties. Thus, autoantibodies targeting excitatory NMDAR or inhibitory GABAaR trigger convergent network dysfunctions through a combination of shared and distinct mechanisms.

Developmental Windows for Effects of Choline and Folate on Excitatory and Inhibitory Neurotransmission During Human Gestation

Choline and folate are critical nutrients for fetal brain development, but the timing of their influence during gestation has not been previously characterized. At different periods during gestation, choline stimulation of α7-nicotinic receptors facilitates conversion of γ-aminobutyric acid (GABA) receptors from excitatory to inhibitory and recruitment of GluR1-R2 receptors for faster excitatory responses to glutamate. The outcome of the fetal development of inhibition and excitation was assessed in 159 newborns by P50 cerebral auditory-evoked responses. Paired stimuli, S1, S2, were presented 500 msec apart. Higher P50 amplitude in response to S1 (P50S1microV) assesses excitation, and lower P50S2microV assesses inhibition in this paired-stimulus paradigm. Development of inhibition was related solely to maternal choline plasma concentration and folate supplementation at 16 weeks' gestation. Development of excitation was related only to maternal choline at 28 weeks. Higher maternal choline concentrations later in gestation did not compensate for earlier lower concentrations. At 4 years of age, increased behavior problems on the Child Behavior Checklist 1½-5yrs were related to both newborn inhibition and excitation. Incomplete development of inhibition and excitation associated with lower choline and folate during relatively brief periods of gestation thus has enduring effects on child development.

Fast signaling by glucocorticoids shapes neural representations of behaviors

Glucocorticoids are stress hormones that play central roles in the immediate and slower adaptive responses of the brain and body to new behavioral experience. The exact mechanisms by which the rapid and slow processes underlying glucocorticoid mnemonic effects unfold are under intensive scrutiny. It is possible that glucocorticoids rapidly modify memory representations in the brain by interfering with synaptic functions between inhibitory and excitatory neurons in a timing and context dependent manner. In particular, activity-dependent trans-synaptic messengers appear to have all the necessary attributes to engage in the rapid signaling by glucocorticoids and regulate the brain and behaviors. Novel frameworks for the treatment of stress-related disorders could emerge from a better characterization of the dynamic interplay between the rapid and slow signaling components by glucocorticoids on large-scale brain networks. Here I present some of the exact factors that could help reach this objective.

Impact of stress on excitatory and inhibitory markers of adolescent cognitive critical period plasticity

Adolescence is a time of significant neurocognitive development. Prolonged maturation of prefrontal cortex (PFC) through adolescence has been found to support improvements in executive function. Changes in excitatory and inhibitory mechanisms of critical period plasticity have been found to be present in the PFC through adolescence, suggesting that environment may have a greater effect on development during this time. Stress is one factor known to affect neurodevelopment increasing risk for psychopathology. However, less is known about how stress experienced during adolescence could affect adolescent-specific critical period plasticity mechanisms and cognitive outcomes. In this review, we synthesize findings from human and animal literatures looking at the experience of stress during adolescence on cognition and frontal excitatory and inhibitory neural activity. Studies indicate enhancing effects of acute stress on cognition and excitation within specific contexts, while chronic stress generally dampens excitatory and inhibitory processes and impairs cognition. We propose a model of how stress could affect frontal critical period plasticity, thus potentially altering neurodevelopmental trajectories that could lead to risk for psychopathology.

Molecular modeling of the structural, electronic, excited state dynamic, and the photovoltaic properties of the oligomers of n-corannulene (n = 1-4)

Despite the fact that n-corannulene oligomers (n = 1-4) have a variety of electronic and optical properties, including the ability to be tuned and the potential to be used as light-harvesting materials, there has not been a computational assessment of their structural, electronic, and optical properties. Herein, a computational evaluation of the concerned materials regarding their potent use in solar cell technology has been conducted via DFT/CAM-B3LYP and M062X/6-311+G level of theory. It was observed that the calculated 1st frequency of the n-Corannulene (n = 1-4) were 144.15, 106.36, 48.96 and 42.21 respectively. Notably, the computed cohesive energy value increased as the number of Corannulene units increases while the electronic characteristics revealed that the chemical activity of the structures increased as the number of oligomers rose. Both calculation techniques demonstrate that the number of n-Corannulene oligomers increases the HOMO energy while decreasing the LUMO energy based on the external electric field (EF) effect. The findings demonstrated that as EF intensity increases, the energy gap (Eg/eV = |EHOMO-ELUMO|) of these molecular systems decreases which can be attributed to a decrease in the electron transfer potential barrier. The 4-Corannulene systems showed the highest wave length of adsorption for the investigated compound at 546.18 nm, with the highest oscillator strength of 0.2708 and the lowest transition energy of 2.2700 eV, arising from S0-S1 (H-L) and the highest major percentage contribution of 93.34 % in comparison to the investigated compounds. We are hopeful that this research will help experimental researchers understand the potential of n-Corannulene, specifically 4-corannulene, as powerful material for a variety of applications ranging from solar cell, photovoltaic properties and many others.

Presubiculum principal cells are preserved from degeneration in knock-in APP/TAU mouse models of Alzheimer's disease

The presubiculum (PRS) is an integral component of the perforant pathway that has recently been recognised as a relatively unscathed region in clinical Alzheimer's disease (AD), despite neighbouring components of the perforant pathway, CA1 and the entorhinal cortex, responsible for formation of episodic memory and storage, showing severe hallmarks of AD including, amyloid-beta (Aβ) plaques, tau tangles and marked gliosis. However, the question remains whether this anatomical resilience translates into functional resilience of the PRS neurons. Using neuroanatomy combined with whole-cell electrophysiological recordings, we investigated whether the unique spatial profile of the PRS was replicable in two knock-in mouse models of AD, APPNL-F/NL-F, and APPNL-F/MAPTHTAU and whether the intrinsic properties and morphological integrity of the PRS principal neurons was maintained compared to the lateral entorhinal cortex (LEC) and hippocampal CA1 principal cells. Our data revealed an age-dependent Aβ and tau pathology with neuroinflammation in the LEC and CA1, but a presence of fleece-like Aβ deposits with an absence of tau tangles and cellular markers of gliosis in the PRS of the mouse models at 11-16 and 18-22 months. These observations were consistent in human post-mortem AD tissue. This spatial profile also correlated with functional resilience of strong burst firing PRS pyramidal cells that showed unaltered sub- and suprathreshold intrinsic biophysical membrane properties and gross morphology in the AD models that were similar to the properties of pyramidal cells recorded in age-matched wild-type mice (11-14 months). This was in contrast to the LEC and CA1 principal cells which showed altered subthreshold intrinsic properties such as a higher input resistance, longer membrane time constants and hyperexcitability in response to suprathreshold stimulation that correlated with atrophied dendrites in both AD models. In conclusion, our data show for the first time that the unique anatomical profile of the PRS constitutes a diffuse AD pathology that is correlated with the preservation of principal pyramidal cell intrinsic biophysical and morphological properties despite alteration of LEC and CA1 pyramidal cells in two distinct genetic models of AD. Understanding the underlying mechanisms of this resilience could be beneficial in preventing the spread of disease pathology before cognitive deficits are precipitated in AD.

Age-related changes in excitatory and inhibitory intra-cortical circuits in auditory cortex of C57Bl/6 mice

A common impairment in aging is age-related hearing loss (presbycusis), which manifests as impaired spectrotemporal processing. Aging is accompanied by alteration in normal inhibitory (GABA) neurotransmission, and changes in excitatory (NMDA and AMPA) synapses in the auditory cortex (ACtx). However, the circuits affected by these synaptic changes remain unknown. Mice of the C57Bl/6J strain show premature age-related hearing loss and changes in functional responses in ACtx. We thus investigated how auditory cortical microcircuits change with age by comparing young (∼ 6 weeks) and aged (>1 year old) C57Bl/6J mice. We performed laser scanning photostimulation (LSPS) combined with whole-cell patch clamp recordings from Layer (L) 2/3 cells in primary auditory cortex (A1) of young adult and aged C57Bl/6J mice. We found that L2/3 cells in aged C57Bl/6J mice display functional hypoconnectivity of both excitatory and inhibitory circuits. Compared to cells from young C57Bl/6 mice, cells from aged C57Bl/6J mice have fewer excitatory connections with weaker connection strength. Whereas young adult and aged C57Bl/6J mice have similar amounts of inhibitory connections, the strength of local inhibition is weaker in the aged group. We confirmed these results by recording miniature excitatory (mEPSCs) and inhibitory synaptic currents (mIPSCs). Our results suggest a specific reduction in excitatory and inhibitory intralaminar cortical circuits in aged C57Bl/6J mice compared with young adult animals. We speculate that these unbalanced changes in cortical circuits contribute to the functional manifestations of age-related hearing loss.

Onset-offset cortical auditory evoked potential amplitude differences indicate auditory cortical hyperactivity and reduced inhibition in people with tinnitus

OBJECTIVE

The current study investigates evidence of hypothesized reduced central inhibition and/or increased excitation in individuals with tinnitus by evaluating cortical auditory onset versus offset responses.

METHODS

Cortical auditory evoked potentials (CAEPs) were recorded to the onset and offset of 3-second white noise stimuli in tinnitus and control groups matched in pairs by age, hearing, and sex (n = 26 total). Independent t-tests and 2-way mixed model ANOVA were used to evaluate onset-offset differences in amplitude, area, and latency of CAEP components by group. The predictive influence of tinnitus presence and associated participant characteristics on CAEP outcomes was assessed by multiple regression proportional reduction in error.

RESULTS

The tinnitus group had significantly larger onset minus offset P2 amplitudes (ΔP2 amplitudes) than control group participants. No other component variables differed significantly. ΔP2 amplitude was best predicted by tinnitus status and not significantly influenced by other variables such as hearing loss or age.

CONCLUSIONS

Hypothesized reduced central inhibition and/or increased excitation in tinnitus participants was partially supported by a group difference in ΔP2 amplitude.

SIGNIFICANCE

This was the first study to evaluate CAEP onset minus offset differences to investigate changes in central excitation/inhibition in individuals with tinnitus versus controls in matched groups.

The CaV1.2 G406R mutation decreases synaptic inhibition and alters L-type Ca2+ channel-dependent LTP at hippocampal synapses in a mouse model of Timothy Syndrome

Genetic alterations in autism spectrum disorders (ASD) frequently disrupt balance between synaptic excitation and inhibition and alter plasticity in the hippocampal CA1 region. Individuals with Timothy Syndrome (TS), a genetic disorder caused by CaV1.2 L-type Ca2+ channel (LTCC) gain-of function mutations, such as G406R, exhibit social deficits, repetitive behaviors, and cognitive impairments characteristic of ASD that are phenocopied in TS2-neo mice expressing G406R. Here, we characterized hippocampal CA1 synaptic function in male TS2-neo mice and found basal excitatory transmission was slightly increased and inhibitory transmission strongly decreased. We also found distinct impacts on two LTCC-dependent forms of long-term potentiation (LTP) synaptic plasticity that were not readily consistent with LTCC gain-of-function. LTP induced by high-frequency stimulation (HFS) was strongly impaired in TS2-neo mice, suggesting decreased LTCC function. Yet, CaV1.2 expression, basal phosphorylation, and current density were similar for WT and TS2-neo. However, this HFS-LTP also required GABAA receptor activity, and thus may be impaired in TS2-neo due to decreased inhibitory transmission. In contrast, LTP induced in WT mice by prolonged theta-train (PTT) stimulation in the presence of a β-adrenergic receptor agonist to increase CaV1.2 phosphorylation was partially induced in TS2-neo mice by PTT stimulation alone, consistent with increased LTCC function. Overall, our findings provide insights regarding how altered CaV1.2 channel function disrupts basal transmission and plasticity that could be relevant for neurobehavioral alterations in ASD.

Band-selective universal 90° and 180° rotation pulses covering the aliphatic carbon chemical shift range for triple resonance experiments on 1.2 GHz spectrometers

Biomolecular NMR spectroscopy requires large magnetic field strengths for high spectral resolution. Today's highest fields comprise proton Larmor frequencies of 1.2 GHz and even larger field strengths are to be expected in the future. In protein triple resonance experiments, various carbon bandwidths need to be excited by selective pulses including the large aliphatic chemical shift range. When the spectrometer field strength is increased, the length of these pulses has to be decreased by the same factor, resulting in higher rf-amplitudes being necessary in order to cover the required frequency region. Currently available band-selective pulses like Q3/Q5 excite a narrow bandwidth compared to the necessary rf-amplitude. Because the maximum rf-power allowed in probeheads is limited, none of the selective universal rotation pulses reported so far is able to cover the full [Formula: see text]C aliphatic region on 1.2 GHz spectrometers. In this work, we present band-selective 90° and 180° universal rotation pulses (SURBOP90 and SURBOP180) that have a higher ratio of selective bandwidth to maximum rf-amplitude than standard pulses. Simulations show that these pulses perform better than standard pulses, e. g. Q3/Q5, especially when rf-inhomogeneity is taken into account. The theoretical and experimental performance is demonstrated in offset profiles and by implementing the SURBOP pulses in an HNCACB experiment at 1.2 GHz.

Sub-MHz bursts of nanosecond pulses excite neurons at paradoxically low electric field thresholds without membrane damage

Neuromodulation applications of nanosecond electric pulses (nsEP) are hindered by their low potency to elicit action potentials in neurons. Excitation by a single nsEP requires a strong electric field which injures neurons by electroporation. We bypassed the high electric field requirement by replacing single nsEP stimuli with high-frequency brief nsEP bursts. In hippocampal neurons, excitation thresholds progressively decreased at nsEP frequencies above 20-200 kHz, with up to 20-30-fold reduction at sub-MHz and MHz rates. For a fixed burst duration, thresholds were determined by the duty cycle, irrespective of the specific nsEP duration, rate, or number of pulses per burst. For 100-μs bursts of 100-, 400-, or 800-ns pulses, the threshold decreased as a power function when the duty cycle exceeded 3-5 %. nsEP bursts were compared with single "long" pulses whose duration and amplitude matched the duration and the time-average amplitude of the burst. Such pulses deliver the same electric charge as bursts, within the same time interval. High-frequency nsEP bursts excited neurons at the time-average electric field 2-3 times below the threshold for a single long pulse. For example, the excitation threshold of 139 ± 14 V/cm for a single 100-μs pulse decreased to 57 ± 8 V/cm for a 100-μs burst of 100-ns, 0.25-MHz pulses (p < 0.001). Applying nsEP in bursts reduced or prevented the loss of excitability in multiple stimulation attempts. Stimulation by high-frequency nsEP bursts is a powerful novel approach to excite neurons at paradoxically low electric charge while also avoiding the electroporative membrane damage.

Varying magnetic field strength as an effective approach to boost up the plasma signal in laser-induced breakdown spectroscopy

Externally variable magnetic field was incorporated with the combination of laser induced breakdown spectroscopy (LIBS) to enhance the emission characteristics of aluminum (Al) plasma. Significant emission enhancement of laser induced plasma (LIP) was obtained at different magnetic field strengths, for instance, enhancement factors of about 1.2, 1.3 and 1.4 times were observed at field-strength of 0.4, 0.5 and 0.6 T, respectively. The electron-impact excitation rates and recombination process were increased at higher field-strengths, which led to the higher emission signal due the stronger plasma confinement by the field. The electron number density and electron temperature were measured using the spectroscopic techniques at several delay times. At higher field strengths, both electron density and electron excitation temperature showed an increased trend as compared to the case when No-field was applied. Hence, the research has significance for enhancing the plasma signal which led to improve the LIBS sensitivity.

The glucocorticoid footprint on the memory engram

The complexity of the classical inverted U-shaped relationship between cortisol levels and responses transposable to stress reactivity has led to an incomplete understanding of the mechanisms enabling healthy and toxic effects of stress on brain and behavior. A clearer, more detailed, picture of those relationships can be obtained by integrating cortisol effects on large-scale brain networks, in particular, by focusing on neural network configurations from the perspective of inhibition and excitation. A unifying view of Semon and Hebb's theories of cellular memory links the biophysical and metabolic changes in neuronal ensembles to the strengthening of collective synapses. In that sense, the neuronal capacity to record, store, and retrieve information directly relates to the adaptive capacity of its connectivity and metabolic reserves. Here, we use task-activated cell ensembles or simply engram cells as an example to demonstrate that the adaptive behavioral responses to stress result from collective synapse strength within and across networks of interneurons and excitatory ones.

Fluorescence spectrophotometry for COVID-19 determination in clinical swab samples

Considering the limitations of the assays currently available for the detection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and its emerging variants, a simple and rapid method using fluorescence spectrophotometry was developed to detect coronavirus disease 2019 (COVID-19). Forty clinical swab samples were collected from the nasopharyngeal and oropharyngeal cavities of COVID-19-positive and -negative. Each sample was divided into two parts. The first part of the samples was analyzed using reverse transcription-polymerase chain reaction (RT-qPCR) as the control method to identify COVID-19-positive and -negative samples. The second part of the samples was analyzed using fluorescence spectrophotometry. Fluorescence measurements were performed at excitation and emission wavelengths ranging from 200 to 800 nm. Twenty COVID-19-positive samples and twenty COVID-19-negative samples were detected based on RT-qPCR results. The fluorescence spectrum data indicated that the COVID-19-positive and -negative samples had significantly different characteristics. All positive samples could be distinguished from negative samples by fluorescence spectrophotometry. Principal component analysis showed that COVID-19-positive samples were clustered separately from COVID-19-negative samples. The specificity and accuracy of this experiment reached 100%. Limit of detection (LOD) obtained 42.20 copies/ml (Ct value of 33.65 cycles) for E gene and 63.60 copies/ml (Ct value of 31.36 cycles) for ORF1ab gene. This identification process only required 4 min. Thus, this technique offers an efficient and accurate method to identify an individual with active SARS-CoV-2 infection and can be easily adapted for the early investigation of COVID-19, in general.

Modelling ethnogenesis

One of the fundamental problems of contemporary history is to understand the processes governing the rise and fall of polities. The universality of boom-and-bust dynamics associated with the life-cycle of polities tempts to treat the problem mathematically and thus brings it to the framework of cliodynamics. Here we introduce a mathematical model of evolving polity under assumption that its evolution is associated with interactions of certain groups of people, forming the polity and differing by their psycho-ethic characteristics. The model is given in terms of ordinary differential equations and the bust dynamics associated with the rise and fall of polities is modelled as an excitation process, which is the non-linear phenomenon, well known in mathematical biology. We consider the deterministic as well as the stochastic version of the model which we fit to the time-scale of civilization's lifespan. We also expand the model to study interaction between two evolving polities. Investigation is performed using analytical methods as well as numerical integration (i.e. MATLAB simulation).

Acriflavine in aqueous solution: excitation and hydration

Using TD-DFT/DFT, the ground and excited states of the acriflavine dye were studied in an aqueous medium. The mutual influence of photoexcitation and strong hydrogen bonds with the solvent was studied by comparing the purely implicit and combined modeling of the aqueous environment of the dye. The excitation of acriflavine was calculated considering the vibronic coupling. The effect of photoexcitation on dye vibrations was analyzed. The spatial structure of the acriflavine H-dimer was obtained and its absorption was estimated.

Identifying novel biomarkers with TMS-EEG - Methodological possibilities and challenges

Biomarkers are essential for understanding the underlying pathologies in brain disorders and for developing effective treatments. Combined transcranial magnetic stimulation and electroencephalography (TMS-EEG) is an emerging neurophysiological tool that can be used for biomarker development. This method can identify biomarkers associated with the function and dynamics of the inhibitory and excitatory neurotransmitter systems and effective connectivity between brain areas. In this review, we outline the current state of the TMS-EEG biomarker field by summarizing the existing protocols and the possibilities and challenges associated with this methodology.

Evaluation of the excited state dynamics, photophysical properties, and the influence of donor substitution in a donor-[Formula: see text]-acceptor system

There have been numerous attempts for the theoretical design of a better donor-[Formula: see text]-acceptor structural framework with improved absorption and emission properties. However, for effective dye designing, it is necessary to understand the electronic and photophysical properties of the dye systems. In this work, we report a detailed density functional theory (DFT) and time-dependent density functional theory (TD-DFT) investigations of the excited state characteristics and the influence of various groups (-HCO, =CH₂, (-CH₃)₂, (HCO)₂, and (-OCH₃)₂) attached to the donor group (-NH₂) in a p-nitroaniline D-[Formula: see text]-A system which are symbolized respectively as p-nitroaniline (A), N,N-dimethylnitroaniline (A2), N,N-dicarbonylnitroaniline (A3), N-methylenenitroaniline (A4), and N,N-dimethoxynitroaniline (A5). The first principles DFT and TD-DFT calculations from the ground state (S₀) to the first five excited states: (S₀→S₁), (S₀→S₂), (S₀→S₃), (S₀→S₄), and (S₀→S₅) were utilized to explore the reactivity of D-[Formula: see text]-A system using the conceptual DFT approach, characterization of electron excitation using the hole-electron analysis, visual study of the various real space functions in the hole-electron framework, density of states (DOS), measurement of charge transfer (CT) length of electron excitation ([Formula: see text]), measurement of the overlapping degrees of hole and electron of electron excitation ([Formula: see text]), interfragment charge transfer (IFCT) during electron excitation, and the second-order perturbation energy analysis from the natural bond orbitals (NBO) computation. Results of the excitation studies show that all the studied compounds exhibited an n→[Formula: see text]* localized type for first excitations (S₀→S₁) on -NO₂ group in A, A2, A4, and A5 and -NCl₂ in A3. [Formula: see text]→[Formula: see text]* charge transfer excitations were confirmed for S₀→S₂/S₄/S₅ in A and A2, S₀→S₃/S₄/S₅ in A3 and A5, and S₀→S₄/S₅ in A4. The NBO second-order perturbation energy analysis suggest that the most significant hyperconjugative interactions were [Formula: see text] (54.43kcal/mol), [Formula: see text] (40.82kcal/mol), [Formula: see text] (11.67kcal/mol), [Formula: see text] (29.52kcal/mol), [Formula: see text] (11.55kcal/mol), [Formula: see text] (23.40kcal/mol), and [Formula: see text] (24.88kcal/mol) [Formula: see text](24.64kcal/mol), which respectively corresponds to the A, A2, A3, A4, and A5 D-[Formula: see text]-A systems under investigation, and these strong interactions stabilize the systems.

Modeling ocean-induced rapid Earth rotation variations: an update

We revisit the problem of modeling the ocean's contribution to rapid, non-tidal Earth rotation variations at periods of 2-120 days. Estimates of oceanic angular momentum (OAM, 2007-2011) are drawn from a suite of established circulation models and new numerical simulations, whose finest configuration is on a ∘ grid. We show that the OAM product by the Earth System Modeling Group at GeoForschungsZentrum Potsdam has spurious short period variance in its equatorial motion terms, rendering the series a poor choice for describing oceanic signals in polar motion on time scales of less than ∼ 2 weeks. Accounting for OAM in rotation budgets from other models typically reduces the variance of atmosphere-corrected geodetic excitation by ∼ 54% for deconvolved polar motion and by ∼ 60% for length-of-day. Use of OAM from the ∘ model does provide for an additional reduction in residual variance such that the combined oceanic-atmospheric effect explains as much as 84% of the polar motion excitation at periods < 120 days. Employing statistical analysis and bottom pressure changes from daily Gravity Recovery and Climate Experiment solutions, we highlight the tendency of ocean models run at a 1 ∘ grid spacing to misrepresent topographically constrained dynamics in some deep basins of the Southern Ocean, which has adverse effects on OAM estimates taken along the 90 ∘ meridian. Higher model resolution thus emerges as a sensible target for improving the oceanic component in broader efforts of Earth system modeling for geodetic purposes.

Disassembly and rewiring of a mature converging excitatory circuit following injury

Specificity and timing of synapse disassembly in the CNS are essential to learning how individual circuits react to neurodegeneration of the postsynaptic neuron. In sensory systems such as the mammalian retina, synaptic connections of second-order neurons are known to remodel and reconnect in the face of sensory cell loss. Here we analyzed whether degenerating third-order neurons can remodel their local presynaptic connectivity. We injured adult retinal ganglion cells by transiently elevating intraocular pressure. We show that loss of presynaptic structures occurs before postsynaptic density proteins and accounts for impaired transmission from presynaptic neurons, despite no evidence of presynaptic cell loss, axon terminal shrinkage, or reduced functional input. Loss of synapses is biased among converging presynaptic neuron types, with preferential loss of the major excitatory cone-driven partner and increased connectivity with rod-driven presynaptic partners, demonstrating that this adult neural circuit is capable of structural plasticity while undergoing neurodegeneration.

Della Santina et al. injure a converging excitatory circuit in the adult retina by intraocular pressure elevation. Postsynaptic retinal ganglion cells disconnect from presynaptic bipolar cells with stereotyped bias against their major partner and rewire with developmental presynaptic partners, underscoring the potential of the adult CNS to adopt developmental patterns.

Ligand gated receptor interactions: A key to the power of neuronal networks

The discovery of the chemical synapse was a seminal finding in Neurobiology but the large body of microscopic interactions involved in synaptic transmission could hardly have been foreseen at the time of these first discoveries. Characterization of the molecular players at work at synapses and the increased granularity at which we can now analyze electrical and chemical signal processing that occur in even the simplest neuronal system are shining a new light on receptor interactions. The aim of this review is to discuss the complexity of some representative interactions between excitatory and inhibitory ligand-gated ion channels and/or G protein coupled receptors, as well as other key machinery that can impact neurotransmission and to explain how such mechanisms can be an important determinant of nervous system function.

Quantitative investigation of memory recall performance of a computational microcircuit model of the hippocampus

Memory, the process of encoding, storing, and maintaining information over time to influence future actions, is very important in our lives. Losing it, it comes with a great cost. Deciphering the biophysical mechanisms leading to recall improvement should thus be of outmost importance. In this study, we embarked on the quest to improve computationally the recall performance of a bio-inspired microcircuit model of the mammalian hippocampus, a brain region responsible for the storage and recall of short-term declarative memories. The model consisted of excitatory and inhibitory cells. The cell properties followed closely what is currently known from the experimental neurosciences. Cells’ firing was timed to a theta oscillation paced by two distinct neuronal populations exhibiting highly regular bursting activity, one tightly coupled to the trough and the other to the peak of theta. An excitatory input provided to excitatory cells context and timing information for retrieval of previously stored memory patterns. Inhibition to excitatory cells acted as a non-specific global threshold machine that removed spurious activity during recall. To systematically evaluate the model’s recall performance against stored patterns, pattern overlap, network size, and active cells per pattern, we selectively modulated feedforward and feedback excitatory and inhibitory pathways targeting specific excitatory and inhibitory cells. Of the different model variations (modulated pathways) tested, ‘model 1’ recall quality was excellent across all conditions. ‘Model 2’ recall was the worst. The number of ‘active cells’ representing a memory pattern was the determining factor in improving the model’s recall performance regardless of the number of stored patterns and overlap between them. As ‘active cells per pattern’ decreased, the model’s memory capacity increased, interference effects between stored patterns decreased, and recall quality improved.

Does high state anxiety exacerbate distractor interference?

Attentional Control Theory states that anxiety can cause attention to be allocated to irrelevant sources of information by hindering the ability to control attention and focus on the information that matters. In a separate line of inquiry, action-centred views of attention state that non-target distractors involuntarily activate response codes that may cause interference with target-directed movements (distractor interference effect). Due to the proposed negative effects of anxiety on attentional control, we examined whether anxiety could also modulate distractor interference. Participants executed target-directed aiming movements to one of three targets with the potential of a distractor being presented at near or far locations. Distractors were presented at different times with respect to the target presentation in order to explore the excitatory (0, -100 ms) and inhibitory (-850 ms) processing of the distractor. As a broad indication of the effect of anxiety, the analysis of no distractor trials indicated a lower proportion of time and displacement to reach peak velocity under high compared to low anxiety conditions. Meanwhile, the typical excitatory influence of the distractors located near, compared to far, at a short distractor-onset asynchrony was found in movement time and overall response time. However, this distractor excitation was even greater under high compared to low anxiety in the reaction time component of the response. These findings broadly implicate the attentional control perspective, but they further indicate an influence of anxiety on the excitation rather than inhibition of responses.

A TD-DFT study of the excited dissociative electronic states of the DNA nucleobases bound to Li. Spectrochim Acta A Mol Biomol Spectrosc 2021;244:118862. [PMID: 32927359 DOI: 10.1016/j.saa.2020.118862]

In this work, the first and second dissociative potential curves of adenineLi⁺ (ADLi⁺), guanineLi⁺ (GUALi⁺), cytosineLi⁺(CYTLi⁺), and thymineLi⁺ (THYLi⁺) complexes, related to the dissociation of their LiO and LiN bonds, have been calculated in the gas phase and water, separately. For this purpose, the fifteen excited potential curves, in order of increasing energy, were calculated for each complex and the dissociative potential curves were distinguished from them considering the conical intersection points. The time-dependent density functional theory (TD-DFT) method employing the M06-2X functional was used for the calculations. It was observed that the electron transfer from the DNA base to the Li⁺ took place during the dissociation of complexes in the gas phase. The electrostatic field of water blocked this charge transfer and led to the excited DNA base and Li⁺ in its ground state. The vertical excitation energy for the desorption of the Li fragment as a neutral and cation species from the DNA bases was determined. The effect of the interaction site of Li⁺ on the dissociative potential curves was also investigated.

Control of synaptic transmission and neuronal excitability in the parabrachial nucleus

•

The parabrachial nucleus (PB) processes intero- and exteroceptive noxious stimuli.

•

Synaptic activity in PB is regulated by GABA_B, µ- and κ-opioid and CB1 receptors.

•

GABAergic presynaptic terminals are most potently regulated by these receptors.

•

Changes in these pathways may promote PB excitability and pathological conditions.

The parabrachial nucleus (PB) is a hub for aversive behaviors, including those related to pain. We have shown that the expression of chronic pain is causally related to amplified activity of PB neurons, and to changes in synaptic inhibition of these neurons. These findings indicate that regulation of synaptic activity in PB may modulate pain perception and be involved in the pathophysiology of chronic pain. Here, we identify the roles in PB of signaling pathways that modulate synaptic functions. In pharmacologically isolated lateral PB neurons in acute mouse slices we find that baclofen, a GABA_B receptor agonist, suppresses the frequency of miniature inhibitory and excitatory postsynaptic currents (mIPSCs and mEPSC). Activation of µ-opioid peptide receptors with DAMGO had similar suppressive effects on excitatory and inhibitory synapses, while the κ-opioid peptide receptor agonist U-69593 suppressed mIPSC release but had no consistent effects on mEPSCs. Activation of cannabinoid type 1 receptors with WIN 55,212-2 reduced the frequency of both inhibitory and excitatory synaptic events, while the CB1 receptor inverse agonist AM251 had opposite effects on mIPSC and mEPSC frequencies. AM251 increased the frequency of inhibitory events but led to a reduction in excitatory events through a GABA_B mediated mechanism. Although none of the treatments produced a consistent effect on mIPSC or mEPSC amplitudes, baclofen and DAMGO both reliably activated a postsynaptic conductance. These results demonstrate that multiple signaling pathways can alter synaptic transmission and neuronal excitability in PB and provide a basis for investigating the contributions of these systems to the development and maintenance of chronic pain.

Optoelectronic properties of diathiafulvalene-functionalized diketopyrrolopyrrole-fullerene molecular dyad

Single component molecular dyad donor-acceptor junction is an important type of organic solar cells. Understanding the optoelectronic properties of molecular dyad plays the critical role to develop active layer materials for such kind of solar cells. Here, diathiafulvalene-functionalized diketopyrrolopyrrole-fullerene (DFDPP-Ful) was selected as the representative system, and the geometries, electronic structures and excitation properties of DFDPP-Ful monomer and dimer were systematically investigated based on extensive quantum chemistry calculations. The transition configurations and molecular orbitals show that the effective electron donor and acceptor are DFDPP and fullerene moieties, respectively. It also found the light harvesting is dominated by local excitation in DFDPP moiety. Meanwhile, the hybridization and quasi-degeneration between charge transfer (CT) and local excitation exist. The dimer data suggest that the increased excited states contribute to the expanding of absorption spectra, and the excitations exhibit both the intermolecular and intra-molecular CTs. Also, the remarkable CT energy differences among the different dimer models for the lowest CT excited states support the strong interface and energy disorder in such system. Therefore, the suggestions for developing molecular dyad of single component organic solar cells would be the combination of increasing light absorption, enhancing CT and local excitation hybridization, as well as suppressing energy and interface disorder by the aid of molecular design.

Revisiting the role of neurotransmitters in epilepsy: An updated review

Epilepsy is a neurologicaldisorder characterized by persistent predisposition to recurrent seizurescaused by abnormal neuronal activity in the brain. Epileptic seizures maydevelop due to a relative imbalance of excitatory and inhibitory neurotransmitters. Expressional alterations of receptors and ion channelsactivated by neurotransmitters can lead to epilepsy pathogenesis.

AIMS

In this updated comprehensive review, we discuss the emerging implication of mutations in neurotransmitter-mediated receptors and ion channels. We aim to provide critical findings of the current literature about the role of neurotransmitters in epilepsy.

MATERIALS AND METHODS

A comprehensive literature review was conducted to identify and critically evaluate studies analyzing the possible relationship between epilepsy and neurotransmitters. The PubMed database was searched for related research articles.

KEY FINDINGS

Glutamate and gamma-aminobutyric acid (GABA) are the main neurotransmitters playing a critical role in the pathophysiology of this balance, and irreversible neuronal damage may occur as a result of abnormal changes in these molecules. Acetylcholine (ACh), the main stimulant of the autonomic nervous system, mediates signal transmission through cholinergic and nicotinic receptors. Accumulating evidence indicates that dysfunction of nicotinic ACh receptors, which are widely expressed in hippocampal and cortical neurons, may be significantly implicated in the pathogenesis of epilepsy. The dopamine-norepinephrine-epinephrine cycle activates hormonal and neuronal pathways; serotonin, norepinephrine, histamine, and melatonin can act as both hormones and neurotransmitters. Recent reports have demonstrated that nitric oxide mediates cognitive and memory-related functions via stimulating neuronal transmission.

SIGNIFICANCE

The elucidation of the role of the main mediators and receptors in epilepsy is crucial for developing new diagnostic and therapeutic approaches.

Synthesis and photophysical properties of multilayer emitting π-p-π fluorophores

Fluorescence is widely used in biology, medicine, and analytical chemistry. The anthracene framework has received considerable attention for the luminescent molecular design as an attractive building unit. Herein, Luminescent "π-p-π" anthracene crystals with different multilayer stacking modes were conducted by experimental methods and theoretical calculations. It was found that "these anthracene derivatives showed strong fluorescence and stability in both solution and solid-state; A face-to-face π-π stacking arrangement dominated in N⁹,N¹⁰-diphenyl-2,6-bis((trimethylsilyl)ethynyl)anthracene-9,10-diamine (4), while C/N-H … π interactions were observed in the crystal lattice of 2,6-diethynyl-N⁹,N¹⁰-diphenylanthracene-9,10-diamine (5); The excitation processes of S₀→S₁ of 4 and 5 belonged to Localized Excitation; The number of photons emitted could be nearly equal to the number of photons absorbed below 120K". This study is expected to assist in the design of photonic materials in the field of optical chemistry.

Cholinergic modulation inhibits cortical spreading depression in mouse neocortex through activation of muscarinic receptors and decreased excitatory/inhibitory drive

Cortical spreading depression (CSD) is a wave of transient network hyperexcitability leading to long lasting depolarization and block of firing, which initiates focally and slowly propagates in the cerebral cortex. It causes migraine aura and it has been implicated in the generation of migraine headache. Cortical excitability can be modulated by cholinergic actions, leading in neocortical slices to the generation of rhythmic synchronous activities (UP/DOWN states). We investigated the effect of cholinergic activation with the cholinomimetic agonist carbachol on CSD triggered with 130 mM KCl pulse injections in acute mouse neocortical brain slices, hypothesizing that the cholinergic-induced increase of cortical network excitability during UP states could facilitate CSD. We observed instead an inhibitory effect of cholinergic activation on both initiation and propagation of CSD, through the action of muscarinic receptors. In fact, carbachol-induced CSD inhibition was blocked by atropine or by the preferential M1 muscarinic antagonist telenzepine; the preferential M1 muscarinic agonist McN-A-343 inhibited CSD similarly to carbachol, and its effect was blocked by telenzepine. Recordings of spontaneous excitatory and inhibitory post-synaptic currents in pyramidal neurons showed that McN-A-343 induced overall a decrease of the excitatory/inhibitory ratio. This inhibitory action may be targeted for novel pharmacological approaches in the treatment of migraine with muscarinic agonists.

Sexual dysfunction and satisfaction in obsessive compulsive disorder: protocol for a systematic review and meta-analysis

BACKGROUND

Obsessive compulsive disorder (OCD) is a chronic mental health condition recognized as one of the most serious causes of disability and impaired quality of life. In the literature, there is no review about sexual dysfunction and satisfaction in OCD. The current paper presents the protocol for a systematic review and meta-analysis aimed to summarize data (1) comparing the presence of sexual dysfunction between groups with OCD and non-clinical groups, (2) investigating prevalence of each one of the sexual dysfunctions in patients with OCD, (3) comparing risk for sexual dysfunction in OCD groups with the prevalence in control groups, (4) comparing sexual satisfaction between OCD groups and non-clinical groups, and (5) investigating moderators of sexual dysfunction in OCD groups as compared with control groups. Gender, age, marital status, OCD symptom severity and subtypes, comorbid depressive disorders, comorbid anxiety disorders, concurrent psychiatric medications, comorbid general medical disease, and study quality will be investigated as moderators.

METHODS

The protocol is reported according to PRISMA-P guidelines. The search will be conducted by independent reviewers during the second week of December 2019 by using electronic databases (Scopus, PubMed, EMBASE, PsycINFO, CINAHL, and the Cochrane Library), by contacting the authors of the included studies to identify further data, by examining the references of the included studies, and by handsearching conference proceedings and theses/doctoral dissertations. The study quality will be independently evaluated using the Newcastle-Ottawa Quality Assessment Scale. Random-effect meta-analyses will be computed. If there is insufficient data for a specific outcome, only a systematic review will be performed.

DISCUSSION

This review may support clinical practice highlighting the importance of the assessment of sexuality in patients with OCD and suggesting the use of therapeutic strategies dedicated to sexuality in this clinical population with the aim of improving patients' quality of life. Potential limitations will regard the heterogeneity of the studies in terms of the instruments used to assess sexual dysfunction/satisfaction and of the definitions used to conceptualize sexual dysfunction.

SYSTEMATIC REVIEW REGISTRATION

Prospero CRD42019132264.

Time in the motor cortex: Motor evoked potentials track foreperiod duration without concurrent movement

Transcranial magnetic stimulation (TMS) allows for the monitoring of motor cortex dynamics in preparation for response. Using this method, it has previously been shown that motor evoked potentials (MEPs) are suppressed as a response approaches. In the current article, we applied TMS while participants either relaxed or contracted their first dorsal interosseous muscle. We varied the time at which TMS was applied, however, unlike previous studies, no participant response was required. Using this method, we provide evidence that MEPs systematically decrease with the duration of the trial, while inhibition is not similarly affected. Further, we found some evidence that MEPs are inversely proportional to the duration of the prior trial. These findings have ramifications for other research interested in the application of TMS, especially when used across multiple possible points in a trial. Further, this finding shows a role for the motor cortex in timing more broadly.

Altered Transcranial Magnetic Stimulation-Electroencephalographic Markers of Inhibition and Excitation in the Dorsolateral Prefrontal Cortex in Major Depressive Disorder

BACKGROUND

The neurophysiology of major depressive disorder (MDD) has become a particular focus of transcranial magnetic stimulation (TMS) investigational studies. TMS combined with electroencephalography (TMS-EEG) affords a window to directly measure evoked activity from the dorsolateral prefrontal cortex (DLPFC), which is of considerable interest in MDD. Our study examined TMS-EEG responses from the DLPFC in persons with MDD compared with those in healthy participants. Specifically, we examined TMS-EEG markers linked to inhibitory and excitatory neurophysiological processes and their balance.

METHODS

In all, 30 participants with MDD and 30 age- and sex-matched healthy participants underwent single-pulse TMS-EEG to assess inhibition and excitation from DLPFC. TMS-EEG waveforms were analyzed through global mean field amplitude.

RESULTS

MDD participants demonstrated abnormalities in TMS-EEG markers in the DLPFC. Inhibitory measures-N45 and N100-were larger in the MDD group than in healthy participants (N45 [t = -4.894, p < .001] and N100 [t = -3.496, p = .001]). In a receiver operating characteristic analysis, N45 amplitude predicted depression illness state with 80% sensitivity, 73.3% specificity, and 76.6% accuracy (area under the curve = 0.829, p < .001). The global mean field amplitude area under the curve, a neurophysiological measure of cortical reactivity, was significantly larger in persons with MDD (t = -3.114, p = .003), as was P60 (t = -3.260, p = .002). In healthy participants, there was a positive correlation between inhibitory N45 and excitatory global mean field amplitude area under the curve (r = .711, p < .001) that was not present in persons with MDD (r = .149, p = .43), demonstrating a potential imbalance between inhibition and excitation in MDD.

CONCLUSIONS

As the TMS-EEG waveform and its components index inhibitory and excitatory activity from the cortex, our results suggest abnormalities in these neurophysiological processes of DLPFC in persons with MDD.

Optimizing channel selection for excitation-scanning hyperspectral imaging

A major benefit of fluorescence microscopy is the now plentiful selection of fluorescent markers. These labels can be chosen to serve complementary functions, such as tracking labeled subcellular molecules near demarcated organelles. However, with the standard 3 or 4 emission channels, multiple label detection is restricted to segregated regions of the electromagnetic spectrum, as in RGB coloring. Hyperspectral imaging allows the user to discern many fluorescence labels by their unique spectral properties, provided there is significant differentiation of their emission spectra. The cost of this technique is often an increase in gain or exposure time to accommodate the signal reduction from separating the signal into many discrete excitation or emission channels. Recent advances in hyperspectral imaging have allowed the acquisition of more signal in a shorter time period by scanning the excitation spectra of fluorophores. Here, we explore the selection of optimal channels for both significant signal separation and sufficient signal detection using excitation-scanning hyperspectral imaging. Excitation spectra were obtained using a custom inverted microscope (TE-2000, Nikon Instruments) with a Xe arc lamp and thin film tunable filter array (VersaChrome, Semrock, Inc.) Tunable filters had bandwidths between 13 and 17 nm. Scans utilized excitation wavelengths between 340 nm and 550 nm. Hyperspectral image stacks were generated and analyzed using ENVI and custom MATLAB scripts. Among channel consideration criteria were: number of channels, spectral range of scan, spacing of center wavelengths, and acquisition time.

Dynamic 23Na MRI - A non-invasive window on neuroglial-vascular mechanisms underlying brain function

A novel magnetic resonance imaging (MRI) acquisition and reconstruction method for obtaining a series of dynamic sodium ²³Na-MRI acquisitions was designed to non-invasively assess the signal variations of brain sodium during a hand motor task in 14 healthy human volunteers on an ultra high field (7T) MR scanner. Regions undergoing activation and deactivation were identified with reference to conventional task-related BOLD functional MRI (fMRI). Activation observed in the left central regions, the supplementary motor areas and the left cerebellum induced an increase in the sodium signal observed at ultra short echo time and a decrease in the ²³Na signal observed at long echo time. Based on a simple model of two distinct sodium pools (namely, restricted and mobile sodium), the ultra short echo time measures the totality of sodium whereas the long echo time is mainly sensitive to mobile sodium. This activation pattern is consistent with previously described processes related to an influx of Na⁺ into the intracellular compartments and a moderate increase in the cerebral blood volume (CBV). In contrast, deactivation observed in the right central regions ipsilateral to the movement, the precuneus and the left cerebellum induced a slight decrease in sodium signal at ultra short echo time and an increase of sodium signal at longer echo times. This inhibitory pattern is compatible with a slight decrease in CBV and an efflux of intracellular Na⁺ to the extracellular compartments that may reflect neural dendritic spine and astrocytic shrinkage, and an increase of sodium in the extracellular fraction. In conclusion, cerebral dynamic ²³Na MRI experiments can provide access to the ionic transients following a functional task occurring within the neuro-glial-vascular ensemble. This has the potential to open up a novel non-invasive window on the mechanisms underlying brain function.

SPEKcheck - fluorescence microscopy spectral visualisation and optimisation: a web application, javascript library, and data resource

Advanced fluorescence imaging methods require careful matching of excitation sources, dichroics, emission filters, detectors, and dyes to operate at their best. This complex task is often left to guesswork, preventing optimal dye:filter combinations, particularly for multicolour applications. To overcome this challenge we developed SPEKcheck, a web application to visualise the efficiency of the light path in a fluorescence microscope. The software reports values for the excitation efficiency of a dye, the collection efficiency of the emitted fluorescence, and a "brightness" score, allowing easy comparison between different fluorescent labels. It also displays a spectral plot of various elements in the configuration, enabling users to readily spot potential problems such as low efficiency excitation, emission, or high bleedthrough. It serves as an aid to exploring the performance of different dyes and filter sets.

Numerical modelling of acoustic pressure fields to optimize the ultrasonic cleaning technique for cylinders

Fouling build up is a well-known problem in the offshore industry. Accumulation of fouling occurs in different structures, e.g. offshore pipes, ship hulls, floating production platforms. The type of fouling that accumulates is dependent on environmental conditions surrounding the structure itself. Current methods deployed for fouling removal span across hydraulic, chemical and manual, all sharing the common disadvantage of necessitating halting production for the cleaning process to commence. Conventionally, ultrasound is used in ultrasonic baths to clean a submerged component by the generation and implosion of cavitation bubbles on the fouled surface; this method is particularly used in Reverse Osmosis applications. However, this requires the submersion of the fouled structure and thus may require a halt to production. Large fouled structures such as pipelines may not be accommodated. The application of high power ultrasonics is proposed in this work as a means to remove fouling on a structure whilst in operation. The work presented in this paper consists of the development of a finite element analysis model based on successful cleaning results from a pipe fouled with calcite on the inner pipe wall. A Polytec 3D Laser Doppler Vibrometer was used in this investigation to study the fouling removal process. Results show the potential of high power ultrasonics for fouling removal in pipe structures from the wave propagation across the structure under excitation, and are used to validate a COMSOL model to determine cleaning patterns based on pressure and displacement distributions for future transducer array design and optimization.

Enhanced postsynaptic inhibitory strength in hippocampal principal cells in high-performing aged rats

Hyperactivity within the hippocampal formation, frequently observed in aged individuals, is thought to be a potential contributing mechanism to the memory decline often associated with aging. Consequently, we evaluated the postsynaptic strength of excitatory and inhibitory synapses in the granule cells of the dentate gyrus and CA1 pyramidal cells of a rat model of aging, in which each individual was behaviorally characterized as aged impaired (AI) or aged unimpaired (AU, with performance comparable to young (Y) individuals). In hippocampal slices of these 3 aged groups (Y, AI, AU), we found that compared to the young, the miniature excitatory and inhibitory currents (mEPSCs and mIPSCs) were larger in amplitude in the granule cells of the AU group and smaller in the AI group. In contrast, in CA1 cells, neither the mEPSCs nor the mIPSCs were affected by age, whereas the extrasynaptic conductance responsible for tonic inhibition was selectively enhanced in CA1 cells of AU individuals. Tonic inhibition conductance was not affected by age in the granule cells. These results support the notion that upregulation of synaptic inhibition could be a necessary condition for the maintenance of performance during aging. These findings also underscore the notions that successful aging requires adaptive upregulation, not merely the preservation of youthful functionality, and that age effects are not homogeneous across hippocampal subfields.

Efficacy and tolerability of a spray formulation containing Visnadine in women self-reporting sexual symptoms: a randomized double-blind placebo-controlled pilot study

PURPOSE

The aim of this pilot, double-blind, randomized, placebo-controlled study, was to evaluate both the efficacy and the tolerability of a formulation for vulvar application containing Visnadine, a natural extractive substance with vasoactive properties, (ReFeel^® spray, IDI Integratori Dietetici Italiani S.r.l., Italy) in women self-reporting sexual symptoms.

METHODS

Sixty women (age range 18-60 years) volunteered to test the product against placebo (PL): Two puffs in the vulvar area, 10 min before sexual stimulation, for 30 days and for a minimum of six times. The main outcome measure was the improvement of the Female Sexual Function Index (FSFI) score (cut-off ≤ 26.55 for female sexual dysfunction [FSD]). Secondary outcomes were sexual satisfaction and tolerability with the product.

RESULTS

PL group (n = 28) and Visnadine group (n = 30) were comparable for age, sexual function and rate of FSD at baseline (T0). After 1 month (T1), women in Visnadine group scored from 25.0 ± 3.8 to 27.9 ± 2.4 (p < 0.001), whereas no changes were evident in PL group (from 25.4 ± 5.0 to 25.6 ± 4.7). Statistically significant differences at T1 were reported in women with a positive (p < 0.001) or a negative FSD diagnosis (p < 0.01) using active treatment. Women with FSD reported significantly more improvement in satisfaction with their sexual function when treated with Visnadine spray compared to PL (p < 0.001), as well as more excitation (p < 0.001), pleasure (p < 0.001) and less time to reach orgasm (p < 0.003). No significant side effects were evident in both groups.

CONCLUSIONS

On demand, 1-month use of Visnadine spray displayed positive effects on sexual function in women with and without FSD and it was well tolerated. Topical Visnadine may not only be part of multimodal strategies to manage clinically relevant sexual symptoms but also simply to help women to enhance their subjective impaired perception of sexual response.

C. elegans Locomotion: Finding Balance in Imbalance

The excitation-inhibition (E-I) imbalance in neural circuits represents a hallmark of several neuropsychiatric disorders. The tiny nematode Caenorhabditis elegans has emerged as an excellent system to study the molecular mechanisms underlying this imbalance in neuronal circuits. The C. elegans body wall muscles receive inputs from both excitatory cholinergic and inhibitory GABAergic motor neurons at neuromuscular junctions (NMJ), making it an excellent model for studying the genetic and molecular mechanisms required for maintaining E-I balance at the NMJ. The cholinergic neurons form dyadic synapses wherein they synapse onto ipsilateral body wall muscles allowing for muscle contraction as well as onto GABAergic motor neurons that in turn synapse on the contralateral body wall muscles causing muscle relaxation. An alternating wave of contraction and relaxation mediated by excitatory and inhibitory signals maintains locomotion in C. elegans. This locomotory behavior requires an intricate balance between the excitatory cholinergic signaling and the inhibitory GABAergic signaling mechanisms.Studies on the C. elegans NMJ have provided insights into several molecular mechanisms that could regulate this balance in neural circuits. This review provides a discussion on multiple genetic factors including neuropeptides and their receptors, cell adhesion molecules, and other molecular pathways that have been associated with maintaining E-I balance in C. elegans motor circuits. Further, it also discusses the implications of these studies that could help us in understanding the role of E-I balance in mammalian neural circuits and how changes in this balance could give rise to brain disorders.

Epileptiform activity and behavioral arrests in mice overexpressing the calcium channel subunit α2δ-1

The alpha2delta-1 subunit (α2δ-1) of voltage-gated calcium channels is a receptor for astrocyte-secreted thrombospondins that promote developmental synaptogenesis. Alpha2delta-1 receptors are upregulated in models of injury-induced peripheral pain and epileptogenic neocortical trauma associated with an enhancement of excitatory synaptic connectivity. These results lead to the hypothesis that overexpression of α2δ-1 alone in neocortex of uninjured transgenic (TG) mice might result in increased excitatory connectivity and consequent cortical hyperexcitability and epileptiform activity. Whole cell recordings from layer V pyramidal neurons in somatosensory cortical slices of TG mice showed increased frequency and amplitude of miniature and spontaneous EPSCs and prolonged bursts of polysynaptic EPSCs. Epileptiform field potentials were evoked in layers II/III and V of brain slices from TG mice, but not controls. Dual immunoreactivity for Vglut-2 and PSD95 showed increased density of close appositions in TG mice compared to controls, suggesting an increased number of excitatory synapses. Video-EEG monitoring showed that 13/13 implanted TG mice aged >P21, but not controls, had frequent abnormal spontaneous epileptiform events, consisting of variable duration, high amplitude bi-hemispheric irregular bursts of delta activity, spikes and sharp waves lasting many seconds, with a variable peak frequency of ~1-3Hz, associated with behavioral arrest. The epileptiform EEG abnormalities and behavioral arrests were reversibly eliminated by treatment with i.p. ethosuximide. Behavioral seizures, consisting of ~15-30s duration episodes of rigid arched tail and head and body extension, followed by loss of balance and falling, frequently occurred in adult TG mice during recovery from isoflurane-induced anesthesia, but were rare in WT mice. Results show that over-expression of α2δ-1 subunits increases cortical excitatory connectivity and leads to neocortical hyperexcitability and epileptiform activity associated with behavioral arrests in adult TG mice. Similar increases in expression of α2δ-1 in models of cortical injury may play an important role in epileptogenesis.

SIGNIFICANCE

Binding of astrocytic-secreted thrombospondins to their α2δ-1 receptor facilitates excitatory synapse formation and excitatory transmission during cortical development and after injury. Upregulation of α2δ-1 is present in models of injury-induced pain and epileptogenic cortical trauma, along with many other molecular alterations. Here we show that overexpression of α2δ-1 alone in TG mice can enhance excitatory connectivity in neocortex and lead to neural circuit hyperexcitability and episodes of electrographic epileptiform activity, associated with behavioral arrests in transgenic mice. α2δ-1 is the high-affinity receptor for gabapentinoids and a potential target for prophylactic treatment of posttraumatic epilepsy and other disorders in which excessive aberrant excitatory connectivity is a pathophysiological feature.

Neurophysiology and Regulation of the Balance Between Excitation and Inhibition in Neocortical Circuits

Brain function relies on the ability of neural networks to maintain stable levels of activity, while experiences sculpt them. In the neocortex, the balance between activity and stability relies on the coregulation of excitatory and inhibitory inputs onto principal neurons. Shifts of excitation or inhibition result in altered excitability impaired processing of incoming information. In many neurodevelopmental and neuropsychiatric disorders, the excitability of local circuits is altered, suggesting that their pathophysiology may involve shifts in synaptic excitation, inhibition, or both. Most studies focused on identifying the cellular and molecular mechanisms controlling network excitability to assess whether they may be altered in animal models of disease. The impact of changes in excitation/inhibition balance on local circuit and network computations is not clear. Here we report findings on the integration of excitatory and inhibitory inputs in healthy cortical circuits and discuss how shifts in excitation/inhibition balance may relate to pathological phenotypes.

Neuronal excitation and permeabilization by 200-ns pulsed electric field: An optical membrane potential study with FluoVolt dye

Electric field pulses of nano- and picosecond duration are a novel modality for neurostimulation, activation of Ca²⁺ signaling, and tissue ablation. However it is not known how such brief pulses activate voltage-gated ion channels. We studied excitation and electroporation of hippocampal neurons by 200-ns pulsed electric field (nsPEF), by means of time-lapse imaging of the optical membrane potential (OMP) with FluoVolt dye. Electroporation abruptly shifted OMP to a more depolarized level, which was reached within <1ms. The OMP recovery started rapidly (τ=8-12ms) but gradually slowed down (to τ>10s), so cells remained above the resting OMP level for at least 20-30s. Activation of voltage-gated sodium channels (VGSC) enhanced the depolarizing effect of electroporation, resulting in an additional tetrodotoxin-sensitive OMP peak in 4-5ms after nsPEF. Omitting Ca²⁺ in the extracellular solution did not reduce the depolarization, suggesting no contribution of voltage-gated calcium channels (VGCC). In 40% of neurons, nsPEF triggered a single action potential (AP), with the median threshold of 3kV/cm (range: 1.9-4kV/cm); no APs could be evoked by stimuli below the electroporation threshold (1.5-1.9kV/cm). VGSC opening could already be detected in 0.5ms after nsPEF, which is too fast to be mediated by the depolarizing effect of electroporation. The overlap of electroporation and AP thresholds does not necessarily reflect the causal relation, but suggests a low potency of nsPEF, as compared to conventional electrostimulation, for VGSC activation and AP induction.

Generating Purkinje networks in the human heart

The Purkinje network is an integral part of the excitation system in the human heart. Yet, to date, there is no in vivo imaging technique to accurately reconstruct its geometry and structure. Computational modeling of the Purkinje network is increasingly recognized as an alternative strategy to visualize, simulate, and understand the role of the Purkinje system. However, most computational models either have to be generated manually, or fail to smoothly cover the irregular surfaces inside the left and right ventricles. Here we present a new algorithm to reliably create robust Purkinje networks within the human heart. We made the source code of this algorithm freely available online. Using Monte Carlo simulations, we demonstrate that the fractal tree algorithm with our new projection method generates denser and more compact Purkinje networks than previous approaches on irregular surfaces. Under similar conditions, our algorithm generates a network with 1219±61 branches, three times more than a conventional algorithm with 419±107 branches. With a coverage of 11±3mm, the surface density of our new Purkije network is twice as dense as the conventional network with 22±7mm. To demonstrate the importance of a dense Purkinje network in cardiac electrophysiology, we simulated three cases of excitation: with our new Purkinje network, with left-sided Purkinje network, and without Purkinje network. Simulations with our new Purkinje network predicted more realistic activation sequences and activation times than simulations without. Six-lead electrocardiograms of the three case studies agreed with the clinical electrocardiograms under physiological conditions, under pathological conditions of right bundle branch block, and under pathological conditions of trifascicular block. Taken together, our results underpin the importance of the Purkinje network in realistic human heart simulations. Human heart modeling has the potential to support the design of personalized strategies for single- or bi-ventricular pacing, radiofrequency ablation, and cardiac defibrillation with the common goal to restore a normal heart rhythm.

Dipole Excitation: A New Method for Mass Analysis with a Quadrupole Mass Filter

Trajectory calculations are used to investigate peak shapes and ion transmission with a proposed new method of mass analysis with a quadrupole mass filter. Dipole excitation is applied to either the x or the y electrodes, or both, to create bands of instability within the first stability region. With excitation between the y electrodes (near β y  = 0), ions are removed from the low mass side of a peak, and with ion excitation in x (near β x  = 1), ions are removed from the high mass side. The mass resolution can be approximately doubled with comparatively little loss in ion transmission. Ion motion in an ideal quadrupole field and in the field of a quadrupole constructed with round rods has been studied. With an ideal quadrupole field, excitation in y is found to give better peak shape and resolution than excitation in x. With quadrupoles constructed with round rods, excitation in y is found to remove ions from both the low and high mass sides of a peak. The additional higher order multipoles introduced to the quadrupole potential by the use of round rods couple the x motion to the y motion so that exciting the y motion also excites ions in x. Thus, only excitation in y is necessary. Both with an ideal quadrupole field and quadrupoles constructed with round rods, the resolution can be increased ca. ×2 with little loss of transmission. Graphical Abstract ᅟ.

Inferring presynaptic population spiking from single-trial membrane potential recordings

BACKGROUND

The time-varying membrane potential of a cortical neuron contains important information about the network activity. Extracting this information requires separating excitatory and inhibitory synaptic inputs from single-trial membrane potential recordings without averaging across trials.

NEW METHOD

We propose a method to extract the time course of excitatory and inhibitory synaptic inputs to a neuron from a single-trial membrane potential recording. The method takes advantage of the differences in the time constants and the reversal potentials of the excitatory and inhibitory synaptic currents, which allows the untangling of the two conductance types.

RESULTS

We evaluate the applicability of the method on a leaky integrate-and-fire model neuron and find high quality of estimation of excitatory synaptic conductance changes and presynaptic population spikes. Application of the method to a real cortical neuron with known synaptic inputs in a brain slice returns high-quality estimation of the time course of the excitatory synaptic conductance. Application of the method to membrane potential recordings from a cortical pyramidal neuron of an intact brain reveals complex network activity.

COMPARISON WITH EXISTING METHODS

Existing methods are based on repeated trials and thus are limited to estimating the statistical features of synaptic conductance changes, or, when based on single trials, are limited to special cases, have low temporal resolution, or are impractically complicated.

CONCLUSIONS

We propose and test an efficient method for estimating the full time course of excitatory and inhibitory synaptic conductances from single-trial membrane potential recordings. The method is sufficiently simple to ensure widespread use in neuroscience.

Impaired synaptic development in a maternal immune activation mouse model of neurodevelopmental disorders

Both genetic and environmental factors are thought to contribute to neurodevelopmental and neuropsychiatric disorders with maternal immune activation (MIA) being a risk factor for both autism spectrum disorders and schizophrenia. Although MIA mouse offspring exhibit behavioral impairments, the synaptic alterations in vivo that mediate these behaviors are not known. Here we employed in vivo multiphoton imaging to determine that in the cortex of young MIA offspring there is a reduction in number and turnover rates of dendritic spines, sites of majority of excitatory synaptic inputs. Significantly, spine impairments persisted into adulthood and correlated with increased repetitive behavior, an ASD relevant behavioral phenotype. Structural analysis of synaptic inputs revealed a reorganization of presynaptic inputs with a larger proportion of spines being contacted by both excitatory and inhibitory presynaptic terminals. These structural impairments were accompanied by altered excitatory and inhibitory synaptic transmission. Finally, we report that a postnatal treatment of MIA offspring with the anti-inflammatory drug ibudilast, prevented both synaptic and behavioral impairments. Our results suggest that a possible altered inflammatory state associated with maternal immune activation results in impaired synaptic development that persists into adulthood but which can be prevented with early anti-inflammatory treatment.

Sensory modulation disorders in childhood epilepsy

Background

Altered sensory sensitivity is generally linked to seizure-susceptibility in childhood epilepsy but may also be associated to the highly prevalent problems in behavioral adaptation. This association is further suggested by the frequent overlap of childhood epilepsy with autism spectrum disorder (ASD) and attention deficit hyperactivity disorder (ADHD), conditions in which altered behavioral responses to sensory stimuli have been firmly established. A continuum of sensory processing defects due to imbalanced neuronal inhibition and excitation across these disorders has been hypothesizedthat may lead to common symptoms of inadequate modulation of behavioral responses to sensory stimuli. Here, we investigated the prevalence of sensory modulation disorders among children with epilepsy and their relation with symptomatology of neurodevelopmental disorders.

Methods

We used the Sensory Profile questionnaire to assess behavioral responses to sensory stimuli and categorize sensory modulation disorders in children with active epilepsy (aged 4–17 years). We related these outcomes to epilepsy characteristics and tested their association with comorbid symptoms of ASD (Social Responsiveness Scale) and ADHD (Strengths and Difficulties Questionnaire).

Results

Sensory modulation disorders were reported in 49 % of the 158 children. Children with epilepsy reported increased behavioral responses associated with sensory “sensitivity,” “sensory avoidance,” and “poor registration” but not “sensory seeking.” Comorbidity of ASD and ADHD was associated with more severe sensory modulation problems, although 27 % of typically developing children with epilepsy also reported a sensory modulation disorder.

Conclusions

Sensory modulation disorders are an under-recognized problem in children with epilepsy. The extent of the modulation difficulties indicates a substantial burden on daily functioning and may explain an important part of the behavioral distress associated with childhood epilepsy.