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Sökning: WFRF:(Kumar Arvind)

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1.
  • 2019
  • Tidskriftsartikel (refereegranskat)
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2.
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3.
  • Kaur-Kahlon, G., et al. (författare)
  • Response of a coastal tropical pelagic microbial community to changed salinity and temperature
  • 2016
  • Ingår i: Aquatic Microbial Ecology. - 0948-3055 .- 1616-1564. ; 77:1, s. 37-50
  • Tidskriftsartikel (refereegranskat)abstract
    • Studies on the responses of tropical microbial communities to changing hydrographic conditions are presently poorly represented. We present here the results from a mesocosm experiment conducted in southwest (SW) coastal India to investigate how changes in temperature and salinity may affect a coastal tropic microbial community. The onset of algal and bacterial blooms, the maximum production and biomass, and the interrelation between phytoplankton and bacteria were studied in replicated mesocosms. The treatments were set up featuring ambient conditions (28 °C, 35 PSU), hyposalinity (31 PSU), warming (31 °C) and a double manipulated treatment with warming and hyposalinity (31 °C, 31 PSU). The hyposaline treatment had the most considerable influence manifested as significantly lower primary production, and the most dissimilar microphytoplankton species community. The increased temperature acted as a catalyst in the double manipulated treatment and higher primary production was maintained. We investigated the dynamics of the microbial community with a structural equation model approach, and found a significant interrelation between phytoplankton biomass and bacterial abundance. Using this methodology, it became evident that temperature and salinity changes, individually and together, mediate direct and indirect effects that influence different compartments of the microbial loop. In the face of climate change, we suggest that in relatively nutrient replete tropical coastal zones, salinity and temperature changes will affect nutrient assimilation with subsequent significant effects on the quantity of microbial biomass and production.
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4.
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5.
  • Anand, Shreya, et al. (författare)
  • Collapsars as Sites of r-process Nucleosynthesis : Systematic Photometric Near-infrared Follow-up of Type Ic-BL Supernovae
  • 2024
  • Ingår i: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 962:1
  • Tidskriftsartikel (refereegranskat)abstract
    • One of the open questions following the discovery of GW170817 is whether neutron star (NS) mergers are the only astrophysical sites capable of producing r-process elements. Simulations have shown that 0.01–0.1 M⊙ of r-process material could be generated in the outflows originating from the accretion disk surrounding the rapidly rotating black hole that forms as a remnant to both NS mergers and collapsing massive stars associated with long-duration gamma-ray bursts (collapsars). The hallmark signature of r-process nucleosynthesis in the binary NS merger GW170817 was its long-lasting near-infrared (NIR) emission, thus motivating a systematic photometric study of the light curves of broad-lined stripped-envelope (Ic-BL) supernovae (SNe) associated with collapsars. We present the first systematic study of 25 SNe Ic-BL—including 18 observed with the Zwicky Transient Facility and 7 from the literature—in the optical/NIR bands to determine what quantity of r-process material, if any, is synthesized in these explosions. Using semi-analytic models designed to account for r-process production in SNe Ic-BL, we perform light curve fitting to derive constraints on the r-process mass for these SNe. We also perform independent light curve fits to models without the r-process. We find that the r-process-free models are a better fit to the light curves of the objects in our sample. Thus, we find no compelling evidence of r-process enrichment in any of our objects. Further high-cadence infrared photometric studies and nebular spectroscopic analysis would be sensitive to smaller quantities of r-process ejecta mass or indicate whether all collapsars are completely devoid of r-process nucleosynthesis.
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6.
  • Bahuguna, Jyotika, et al. (författare)
  • Existence and control of Go/No-Go decision transition threshold in the striatum
  • 2015
  • Ingår i: PloS Computational Biology. - : PLOS. - 1553-734X .- 1553-7358. ; 11:4
  • Tidskriftsartikel (refereegranskat)abstract
    • A typical Go/No-Go decision is suggested to be implemented in the brain via the activation of the direct or indirect pathway in the basal ganglia. Medium spiny neurons (MSNs) in the striatum, receiving input from cortex and projecting to the direct and indirect pathways express D1 and D2 type dopamine receptors, respectively. Recently, it has become clear that the two types of MSNs markedly differ in their mutual and recurrent connectivities as well as feedforward inhibition from FSIs. Therefore, to understand striatal function in action selection, it is of key importance to identify the role of the distinct connectivities within and between the two types of MSNs on the balance of their activity. Here, we used both a reduced firing rate model and numerical simulations of a spiking network model of the striatum to analyze the dynamic balance of spiking activities in D1 and D2 MSNs. We show that the asymmetric connectivity of the two types of MSNs renders the striatum into a threshold device, indicating the state of cortical input rates and correlations by the relative activity rates of D1 and D2 MSNs. Next, we describe how this striatal threshold can be effectively modulated by the activity of fast spiking interneurons, by the dopamine level, and by the activity of the GPe via pallidostriatal backprojections. We show that multiple mechanisms exist in the basal ganglia for biasing striatal output in favour of either the `Go' or the `No-Go' pathway. This new understanding of striatal network dynamics provides novel insights into the putative role of the striatum in various behavioral deficits in patients with Parkinson's disease, including increased reaction times, L-Dopa-induced dyskinesia, and deep brain stimulation-induced impulsivity.
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7.
  • Bahuguna, Jyotika, et al. (författare)
  • Homologous Basal Ganglia Network Models in Physiological and Parkinsonian Conditions
  • 2017
  • Ingår i: Frontiers in Computational Neuroscience. - : FRONTIERS MEDIA SA. - 1662-5188. ; 11
  • Tidskriftsartikel (refereegranskat)abstract
    • The classical model of basal ganglia has been refined in recent years with discoveries of subpopulations within a nucleus and previously unknown projections. One such discovery is the presence of subpopulations of arkypallidal and prototypical neurons in external globus pallidus, which was previously considered to be a primarily homogeneous nucleus. Developing a computational model of these multiple interconnected nuclei is challenging, because the strengths of the connections are largely unknown. We therefore use a genetic algorithm to search for the unknown connectivity parameters in a firing rate model. We apply a binary cost function derived from empirical firing rate and phase relationship data for the physiological and Parkinsonian conditions. Our approach generates ensembles of over 1,000 configurations, or homologies, for each condition, with broad distributions for many of the parameter values and overlap between the two conditions. However, the resulting effective weights of connections from or to prototypical and arkypallidal neurons are consistent with the experimental data. We investigate the significance of the weight variability by manipulating the parameters individually and cumulatively, and conclude that the correlation observed between the parameters is necessary for generating the dynamics of the two conditions. We then investigate the response of the networks to a transient cortical stimulus, and demonstrate that networks classified as physiological effectively suppress activity in the internal globus pallidus, and are not susceptible to oscillations, whereas parkinsonian networks show the opposite tendency. Thus, we conclude that the rates and phase relationships observed in the globus pallidus are predictive of experimentally observed higher level dynamical features of the physiological and parkinsonian basal ganglia, and that the multiplicity of solutions generated by our method may well be indicative of a natural diversity in basal ganglia networks. We propose that our approach of generating and analyzing an ensemble of multiple solutions to an underdetermined network model provides greater confidence in its predictions than those derived from a unique solution, and that projecting such homologous networks on a lower dimensional space of sensibly chosen dynamical features gives a better chance than a purely structural analysis at understanding complex pathologies such as Parkinson's disease.
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8.
  • Bahuguna, Jyotika (författare)
  • Structure-Dynamics relationship in basalganglia: Implications for brain function
  • 2016
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • In this thesis, I have used a combination of computational models such as mean field and spikingnetwork simulations to study various sub-circuits of basal ganglia. I first studied the striatum(chapter 2), which is the input nucleus of basal ganglia. The two types of Medium SpinyNeurons (MSNs), D1 and D2-MSNs, together constitute 98% of the neurons in striatum. Thecomputational models so far have treated striatum as a homogenous unit and D1 and D2 MSNs asinterchangeable subpopulations. This implied that a bias in a Go/No-Go decision is enforced viaexternal agents to the striatum (eg. cortico-striatal weights), thereby assigning it a passive role.New data shows that there is an inherent asymmetry in striatal circuits. In this work, I showedthat striatum due to its asymmetric connectivity acts as a decision transition threshold devicefor the incoming cortical input. This has significant implications on the function of striatum asan active participant in influencing the bias towards a Go/No-Go decision. The striatal decisiontransition threshold also gives mechanistic explanations for phenomena such as L-Dopa InducedDyskinesia (LID), DBS-induced impulsivity, etc. In chapter 3, I extend the mean field model toinclude all the nuclei of basal ganglia to specifically study the role of two new subpopulationsfound in GPe (Globus Pallidus Externa). Recent work shows that GPe, also earlier consideredto be a homogenous nucleus, has at least two subpopulations which are dichotomous in theiractivity with respect to the cortical Slow Wave (SWA) and beta activity. Since the data for thesesubpopulations are missing, a parameter search was performed for effective connectivities usingGenetic Algorithms (GA) to fit the available experimental data. One major result of this studyis that there are various parameter combinations that meet the criteria and hence the presenceof functional homologs of the basal ganglia network for both pathological (PD) and healthynetworks is a possibility. Classifying all these homologous networks into clusters using somehigh level features of PD shows a large variance, hinting at the variance observed among the PDpatients as well as their response to the therapeutic measures. In chapter 4, I collaborated on aproject to model the role of STN and GPe burstiness for pathological beta oscillations as seenduring PD. During PD, the burstiness in the firing patterns of GPe and STN neurons are shownto increase. We found that in the baseline state, without any bursty neurons in GPe and STN,the GPe-STN network can transition to an oscillatory state through modulating the firing ratesof STN and GPe neurons. Whereas when GPe neurons are systematically replaced by burstyneurons, we found that increase in GPe burstiness enforces oscillations. An optimal % of burstyneurons in STN destroys oscillations in the GPe-STN network. Hence burstiness in STN mayserve as a compensatory mechanism to destroy oscillations. We also propose that bursting inGPe-STN could serve as a mechanism to initiate and kill oscillations on short time scales, asseen in the healthy state. The GPe-STN network however loses the ability to kill oscillations inthe pathological state.
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9.
  • Bahuguna, Jyotika, et al. (författare)
  • Uncoupling the roles of firing rates and spike bursts in shaping the STN-GPe beta band oscillations
  • 2020
  • Ingår i: PloS Computational Biology. - : Public Library of Science. - 1553-734X .- 1553-7358. ; 16:3
  • Tidskriftsartikel (refereegranskat)abstract
    • The excess of 15-30 Hz (beta-band) oscillations in the basal ganglia is one of the key signatures of Parkinson's disease (PD). The STN-GPe network is integral to generation and modulation of beta band oscillations in basal ganglia. However, the role of changes in the firing rates and spike bursting of STN and GPe neurons in shaping these oscillations has remained unclear. In order to uncouple their effects, we studied the dynamics of STN-GPe network using numerical simulations. In particular, we used a neuron model, in which firing rates and spike bursting can be independently controlled. Using this model, we found that while STN firing rate is predictive of oscillations but GPe firing rate is not. The effect of spike bursting in STN and GPe neurons was state-dependent. That is, only when the network was operating in a state close to the border of oscillatory and non-oscillatory regimes, spike bursting had a qualitative effect on the beta band oscillations. In these network states, an increase in GPe bursting enhanced the oscillations whereas an equivalent proportion of spike bursting in STN suppressed the oscillations. These results provide new insights into the mechanisms underlying the transient beta bursts and how duration and power of beta band oscillations may be controlled by an interplay of GPe and STN firing rates and spike bursts. Author summary The STN-GPe network undergoes a change in firing rates as well as increased bursting during excessive beta band oscillations during Parkinson's disease. In this work we uncouple their effects by using a novel neuron model and show that presence of oscillations is contingent on the increase in STN firing rates, however the effect of spike bursting on oscillations depends on the network state. In a network state on the border of oscillatory and non-oscillatory regime, GPe spike bursting strengthens oscillations. The effect of spike bursting in the STN depends on the proportion of GPe neurons bursting. These results suggest a mechanism underlying a transient beta band oscillation bursts often seen in experimental data.
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10.
  • Belic, Jovana, 1987-, et al. (författare)
  • Interactions in the Striatal Network with Different Oscillation Frequencies
  • 2017
  • Ingår i: Artificial Neural Networks and Machine Learning – ICANN. Lecture Notes in Computer Science. - Cham : Springer. - 9783319685991 ; , s. 129-136
  • Konferensbidrag (refereegranskat)abstract
    • Simultaneous oscillations in different frequency bands are implicated in the striatum, and understanding their interactions will bring us one step closer to restoring the spectral characteristics of striatal activity that correspond to the healthy state. We constructed a computational model of the striatum in order to investigate how different, simultaneously present, and externally induced oscillations propagate through striatal circuitry and which stimulation parameters have a significant contribution. Our results show that features of these oscillations and their interactions can be influenced via amplitude, input frequencies, and the phase offset between different external inputs. Our findings provide further untangling of the oscillatory activity that can be seen within the striatal network.
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11.
  • Belić, Jovana, 1987-, et al. (författare)
  • Interplay between periodic stimulation and GABAergic inhibition in striatal network oscillations
  • 2017
  • Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 12:4, s. 1-17
  • Tidskriftsartikel (refereegranskat)abstract
    • Network oscillations are ubiquitous across many brain regions. In the basal ganglia, oscillations are also present at many levels and a wide range of characteristic frequencies have been reported to occur during both health and disease. The striatum, the main input nucleus of the basal ganglia, receives massive glutamatergic inputs from the cortex and is highly susceptible to external oscillations. However, there is limited knowledge about the exact nature of this routing process and therefore, it is of key importance to understand how time-dependent, external stimuli propagate through the striatal circuitry. Using a network model of the striatum and corticostriatal projections, we try to elucidate the importance of specific GABAergic neurons and their interactions in shaping striatal oscillatory activity. Here, we propose that fast-spiking interneurons can perform an important role in transferring cortical oscillations to the striatum especially to those medium spiny neurons that are not directly driven by the cortical oscillations. We show how the activity levels of different populations, the strengths of different inhibitory synapses, degree of outgoing projections of striatal cells, ongoing activity and synchronicity of inputs can influence network activity. These results suggest that the propagation of oscillatory inputs into the medium spiny neuron population is most efficient, if conveyed via the fast-spiking interneurons. Therefore, pharmaceuticals that target fast-spiking interneurons may provide a novel treatment for regaining the spectral characteristics of striatal activity that correspond to the healthy state.
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12.
  • Belic, Jovana, et al. (författare)
  • The role of striatal feedforward inhibition in propagation of cortical oscillations
  • 2017
  • Ingår i: BMC Neuroscience. - Antwerpen. - 1471-2202. ; 18, s. 91-91
  • Tidskriftsartikel (refereegranskat)abstract
    • Fast spiking interneurons (FSIs) and feedforward (FF) inhibition are a common property of neuronal networks throughout the brain and play crucial role in neural computations. For instance, in the cortex FF inhibition sets the window of temporal integration and spiking and thereby contributes to the control of firing rate and correlations [1]. In the striatum (the main input structure of the basal ganglia) despite their high firing rates and strong synapses, FSIs (comprise 1–2% of striatal neurons) do not seem to play a major role in controlling the firing of medium spiny neurons (MSNs; comprise 95% of striatal neurons) [2] and so far, it has not been possible to attribute a functional role to FSIs in the striatum. Here we use a spiking neuron network model in order to investigate how externally induced oscillations propagate through striatal circuitry. Recordings in the striatum have shown robust oscillatory activity that might be in fact cortical oscillations transmitted by the corticostriatal projections [3–5]. We propose that FSIs can perform an important role in transferring cortical oscillations to the striatum especially to those MSNs that are not directly driven by the cortical oscillations. Strong and divergent connectivity of FSIs implies that even weak oscillations in FSI population activity can be spread to the whole MSN population [6]. Further, we have identified multiple factors that influence the transfer of oscillations to MSNs. The variables such as the number of activated neurons, ongoing activity, connectivity, and synchronicity of inputs influence the transfer of oscillations by modifying the levels of feedforward and feedback inhibitions suggesting that the striatum can exploit different parameters to impact the transfer of oscillatory signals.References1. Isaacson, J. S., & Scanziani, M. (2011). How inhibition shapes cortical activity. Neuron, 72(2), 231–243. 2. Berke, J. D. (2011). Functional properties of striatal fast-spiking interneurons. Frontiers in systems neuroscience, 5.3. Belić, J. J., Halje, P., Richter, U., Petersson, P., & Kotaleski, J. H. (2016). Untangling cortico-striatal connectivity and cross-frequency coupling in L-DOPA-induced dyskinesia. Frontiers in systems neuroscience, 10.4. Berke, J. D. (2009). Fast oscillations in cortical‐striatal networks switch frequency following rewarding events and stimulant drugs. European Journal of Neuroscience, 30(5), 848–859.5. Boraud, T., Brown, P., Goldberg, J. A., Graybiel, A. M., & Magill, P. J. (2005). Oscillations in the basal ganglia: the good, the bad, and the unexpected. In The basal ganglia VIII (pp. 1–24). Springer US.6. Belić, J. J., Kumar, A., & Kotaleski, J. H. (2017). Interplay between periodic stimulation and GABAergic inhibition in striatal network oscillations. PloS one, 12(4), e0175135.
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13.
  • Belic, Jovana (författare)
  • Untangling Cortico-Striatal Circuitry and its Role in Health and Disease - A computational investigation
  • 2018
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • The basal ganglia (BG) play a critical role in a variety of regular motor and cognitive functions. Many brain diseases, such as Parkinson’s diseases, Huntington’s disease and dyskinesia, are directly related to malfunctions of the BG nuclei. One of those nuclei, the input nucleus called the striatum, is heavily connected to the cortex and receives afferents from nearly all cortical areas. The striatum is a recurrent inhibitory network that contains several distinct cell types. About 95% of neurons in the striatum are medium spiny neurons (MSNs) that form the only output from the striatum. Two of the most examined sources of GABAergic inhibition into MSNs are the feedback inhibition (FB) from the axon collaterals of the MSNs themselves, and the feedforward inhibition (FF) via the small population (1-2% of striatal neurons) of fast spiking interneurons (FSIs). The cortex sends direct projections to the striatum, while the striatum can affect the cortex only indirectly through other BG nuclei and the thalamus. Understanding how different components of the striatal network interact with each other and influence the striatal response to cortical inputs has crucial importance for clarifying the overall functions and dysfunctions of the BG.    In this thesis I have employed advanced experimental data analysis techniques as well as computational modelling, to study the complex nature of cortico-striatal interactions. I found that for pathological states, such as Parkinson’s disease and L-DOPA-induced dyskinesia, effective connectivity is bidirectional with an accent on the striatal influence on the cortex. Interestingly, in the case of L-DOPA-induced dyskinesia, there was a high increase in effective connectivity at ~80 Hz and the results also showed a large relative decrease in the modulation of the local field potential amplitude (recorded in the primary motor cortex and sensorimotor striatum in awake, freely behaving, 6-OHDA lesioned hemi-parkinsonian rats) at ~80 Hz by the phase of low frequency oscillations. These results suggest a lack of coupling between the low frequency activity of a presumably larger neuronal population and the synchronized activity of a presumably smaller group of neurons active at 80 Hz.    Next, I used a spiking neuron network model of the striatum to isolate the mechanisms underlying the transmission of cortical oscillations to the MSN population. I showed that FSIs play a crucial role in efficient propagation of cortical oscillations to the MSNs that did not receive direct cortical oscillations. Further, I have identified multiple factors such as the number of activated neurons, ongoing activity, connectivity, and synchronicity of inputs that influenced the transfer of oscillations by modifying the levels of FB and FF inhibitions. Overall, these findings reveal a new role of FSIs in modulating the transfer of information from the cortex to striatum. By modulating the activity and properties of the FSIs, striatal oscillations can be controlled very efficiently. Finally, I explored the interactions in the striatal network with different oscillation frequencies and showed that the features of those oscillations, such as amplitude and frequency fluctuations, can be influenced by a change in the input intensities into MSNs and FSIs and that these fluctuations are also highly dependent on the selected frequencies in addition to the phase offset between different cortical inputs.    Lastly, I investigated how the striatum responds to cortical neuronal avalanches. Recordings in the striatum revealed that striatal activity was also characterized by spatiotemporal clusters that followed a power law distribution albeit, with significantly steeper slope. In this study, an abstract computational model was developed to elucidate the influence of intrastriatal inhibition and cortico-striatal interplay as important factors to understand the experimental findings. I showed that one particularly high activation threshold of striatal nodes can reproduce a power law-like distribution with a coefficient similar to the one found experimentally. By changing the ratio of excitation and inhibition in the cortical model, I saw that increased activity in the cortex strongly influenced striatal dynamics, which was reflected in a less negative slope of cluster size distributions in the striatum.  Finally, when inhibition was added to the model, cluster size distributions had a prominently earlier deviation from the power law distribution compared to the case when inhibition was not present. 
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14.
  • Bharmoria, Pankaj, et al. (författare)
  • Do Ionic Liquids Exhibit the Required Characteristics to Dissolve, Extract, Stabilize, and Purify Proteins? Past-Present-Future Assessment
  • 2024
  • Ingår i: Chemical Reviews. - 0009-2665 .- 1520-6890. ; 124:6, s. 3037-3084
  • Forskningsöversikt (refereegranskat)abstract
    • Proteins are highly labile molecules, thus requiring the presence of appropriate solvents and excipients in their liquid milieu to keep their stability and biological activity. In this field, ionic liquids (ILs) have gained momentum in the past years, with a relevant number of works reporting their successful use to dissolve, stabilize, extract, and purify proteins. Different approaches in protein-IL systems have been reported, namely, proteins dissolved in (i) neat ILs, (ii) ILs as co-solvents, (iii) ILs as adjuvants, (iv) ILs as surfactants, (v) ILs as phase-forming components of aqueous biphasic systems, and (vi) IL-polymer-protein/peptide conjugates. Herein, we critically analyze the works published to date and provide a comprehensive understanding of the IL-protein interactions affecting the stability, conformational alteration, unfolding, misfolding, and refolding of proteins while providing directions for future studies in view of imminent applications. Overall, it has been found that the stability or purification of proteins by ILs is bispecific and depends on the structure of both the IL and the protein. The most promising IL-protein systems are identified, which is valuable when foreseeing market applications of ILs, e.g., in “protein packaging” and “detergent applications”. Future directions and other possibilities of IL-protein systems in light-harvesting and biotechnology/biomedical applications are discussed.
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15.
  • Binda, Francesca, et al. (författare)
  • Excitation and Inhibition Delays within a Feedforward Inhibitory Pathway Modulate Cerebellar Purkinje Cell Output in Mice
  • 2023
  • Ingår i: Journal of Neuroscience. - : Society for Neuroscience. - 0270-6474 .- 1529-2401. ; 43:33, s. 5905-5917
  • Tidskriftsartikel (refereegranskat)abstract
    • The cerebellar cortex computes sensorimotor information from many brain areas through a feedforward inhibitory (FFI) microcircuit between the input stage, the granule cell (GC) layer, and the output stage, the Purkinje cells (PCs). Although in other brain areas FFI underlies a precise excitation versus inhibition temporal correlation, recent findings in the cerebellum highlighted more complex behaviors at GC-molecular layer interneuron (MLI)-PC pathway. To dissect the temporal organization of this cerebellar FFI pathway, we combined ex vivo patch-clamp recordings of PCs in male mice with a viral-based strategy to express Channelrhodopsin2 in a subset of mossy fibers (MFs), the major excitatory inputs to GCs. We show that although light-mediated MF activation elicited pairs of excitatory and inhibitory postsynaptic currents in PCs, excitation (E) from GCs and inhibition (I) from MLIs reached PCs with a wide range of different temporal delays. However, when GCs were directly stimulated, a low variability in E/I delays was observed. Our results demonstrate that in many recordings MF stimulation recruited different groups of GCs that trigger E and/or I, and expanded PC temporal synaptic integration. Finally, using a computational model of the FFI pathway, we showed that this temporal expansion could strongly influence how PCs integrate GC inputs. Our findings show that specific E/I delays may help PCs encoding specific MF inputs.SIGNIFICANCE STATEMENT Sensorimotor information is conveyed to the cerebellar cortex by mossy fibers. Mossy fiber inputs activate granule cells that excite molecular interneurons and Purkinje cells, the sole output of the cerebellar cortex, leading to a sequence of synaptic excitation and inhibition in Purkinje cells, thus defining a feedforward inhibitory pathway. Using electrophysiological recordings, optogenetic stimulation, and mathematical modeling, we demonstrated that different groups of granule cells can elicit synaptic excitation and inhibition with various latencies onto Purkinje cells. This temporal variability controls how granule cells influence Purkinje cell discharge and may support temporal coding in the cerebellar cortex.
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16.
  • Boniolo, Manuel, et al. (författare)
  • Electronic and geometric structure effects on one-electron oxidation of first-row transition metals in the same ligand framework
  • 2021
  • Ingår i: Dalton Transactions. - : Royal Society of Chemistry. - 1477-9226 .- 1477-9234. ; 50:2, s. 660-674
  • Tidskriftsartikel (refereegranskat)abstract
    • Developing new transition metal catalysts requires understanding of how both metal and ligand properties determine reactivity. Since metal complexes bearing ligands of the Py5 family (2,6-bis-[(2-pyridyl)methyl] pyridine) have been employed in many fields in the past 20 years, we set out here to understand their redox properties by studying a series of base metal ions (M = Mn, Fe, Co, and Ni) within the Py5OH (pyridine-2,6-diylbis[di-(pyridin-2-yl)methanol]) variant. Both reduced (M-II) and the one-electron oxidized (M-III) species were carefully characterized using a combination of X-ray crystallography, X-ray absorption spectroscopy, cyclic voltammetry, and density-functional theory calculations. The observed metal-ligand interactions and electrochemical properties do not always follow consistent trends along the periodic table. We demonstrate that this observation cannot be explained by only considering orbital and geometric relaxation, and that spin multiplicity changes needed to be included into the DFT calculations to reproduce and understand these trends. In addition, exchange reactions of the sixth ligand coordinated to the metal, were analysed. Finally, by including published data of the extensively characterised Py5OMe (pyridine-2,6-diylbis[di-(pyridin-2-yl)methoxymethane])complexes, the special characteristics of the less common Py5OH ligand were extracted. This comparison highlights the non-innocent effect of the distal OH functionalization on the geometry, and consequently on the electronic structure of the metal complexes. Together, this gives a complete analysis of metal and ligand degrees of freedom for these base metal complexes, while also providing general insights into how to control electrochemical processes of transition metal complexes.
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17.
  • Bujan, Alejandro, et al. (författare)
  • Role of Input Correlations in Shaping the Variability and Noise Correlations of Evoked Activity in the Neocortex
  • 2015
  • Ingår i: Journal of Neuroscience. - 0270-6474 .- 1529-2401. ; 35:22, s. 8611-8625
  • Tidskriftsartikel (refereegranskat)abstract
    • Recent analysis of evoked activity recorded across different brain regions and tasks revealed a marked decrease in noise correlations and trial-by-trial variability. Given the importance of correlations and variability for information processing within the rate coding paradigm, several mechanisms have been proposed to explain the reduction in these quantities despite an increase in firing rates. These models suggest that anatomical clusters and/or tightly balanced excitation-inhibition can generate intrinsic network dynamics that may exhibit a reduction in noise correlations and trial-by-trial variability when perturbed by an external input. Such mechanisms based on the recurrent feedback crucially ignore the contribution of feedforward input to the statistics of the evoked activity. Therefore, we investigated how statistical properties of the feedforward input shape the statistics of the evoked activity. Specifically, we focused on the effect of input correlation structure on the noise correlations and trial-by-trial variability. We show that the ability of neurons to transfer the input firing rate, correlation, and variability to the output depends on the correlations within the presynaptic pool of a neuron, and that an input with even weak within-correlations can be sufficient to reduce noise correlations and trial-by-trial variability, without requiring any specific recurrent connectivity structure. In general, depending on the ongoing activity state, feedforward input could either increase or decrease noise correlation and trial-by-trial variability. Thus, we propose that evoked activity statistics are jointly determined by the feedforward and feedback inputs.
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18.
  • Carannante, Ilaria, et al. (författare)
  • The impact of Parkinson’s disease on striatal network connectivity and cortico-striatal drive : an in-silico study
  • Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
    • Striatum, the input stage of the basal ganglia, is important for sensory-motor integration, initiation and selection of behaviour, as well as reward learning. Striatum receives glutamatergic inputs from mainly cortex and thalamus. In rodents, the striatal projection neurons (SPNs), giving rise to the direct and the indirect pathway (dSPNs and iSPNs, respectively), account for 95% of the neurons and the remaining 5% are GABAergic and cholinergic interneurons. Interneuron axon terminals as well as local dSPN and iSPN axon collaterals form an intricate striatal network. Following chronic dopamine depletion as in Parkinson’s disease (PD), both morphological and electrophysiological striatal neuronal features are altered. Our goal with this \textit{in-silico} study is twofold: a) to predict and quantify how the intrastriatal network connectivity structure becomes altered as a consequence of the morphological changes reported at the single neuron level, and b) to investigate how the effective glutamatergic drive to the SPNs would need to be altered to account for the activity level seen in SPNs during PD. In summary we find that the richness of the connectivity motifs is significantly decreased during PD, while at the same time a substantial enhancement of the effective glutamatergic drive to striatum is present.  
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19.
  • Cenci, M. Angela, et al. (författare)
  • Cells, pathways, and models in dyskinesia research
  • 2024
  • Ingår i: Current Opinion in Neurobiology. - : Elsevier BV. - 0959-4388 .- 1873-6882. ; 84
  • Forskningsöversikt (refereegranskat)abstract
    • L-DOPA-induced dyskinesia (LID) is the most common form of hyperkinetic movement disorder resulting from altered information processing in the cortico-basal ganglia network. We here review recent advances clarifying the altered interplay between striatal output pathways in this movement disorder. We also review studies revealing structural and synaptic changes to the striatal microcircuitry and altered cortico-striatal activity dynamics in LID. We furthermore highlight the recent progress made in understanding the involvement of cerebellar and brain stem nuclei. These recent developments illustrate that dyskinesia research continues to provide key insights into cellular and circuit-level plasticity within the cortico-basal ganglia network and its interconnected brain regions.
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20.
  • Chakravarty, Kingshuk, et al. (författare)
  • Transient Response of Basal Ganglia Network in Healthy and Low-Dopamine State
  • 2022
  • Ingår i: eNeuro. - : Society for Neuroscience. - 2373-2822. ; 9:2, s. ENEURO.0376-21.2022-
  • Tidskriftsartikel (refereegranskat)abstract
    • The basal ganglia (BG) are crucial for a variety of motor and cognitive functions. Changes induced by persistent low-dopamine (e.g., in Parkinson's disease; PD) result in aberrant changes in steady-state population activity (beta band oscillations) and the transient response of the BG. Typically, a brief cortical stimulation results in a triphasic response in the substantia nigra pars reticulata (SNr; an output of the BG). The properties of the triphasic responses are shaped by dopamine levels. While mechanisms underlying aberrant steady state activity are well studied, it is still unclear which BG interactions are crucial for the aberrant transient responses in the BG. Moreover, it is also unclear whether mechanisms underlying the aberrant changes in steady-state activity and transient response are the same. Here, we used numerical simulations of a network model of BG to identify the key factors that determine the shape of the transient responses. We show that an aberrant transient response of the SNr in the low-dopamine state involves changes in the direct pathway and the recurrent interactions within the globus pallidus externa (GPe) and between GPe and subthalamic nucleus (STN). However, the connections from D2-type spiny projection neurons (D2-SPN) to GPe are most crucial in shaping the transient response and by restoring them to their healthy level, we could restore the shape of transient response even in low-dopamine state. Finally, we show that the changes in BG that result in aberrant transient response are also sufficient to generate pathologic oscillatory activity in the steady state.
  •  
21.
  • Chatterjee, Tulika, et al. (författare)
  • Type 1 diabetes, COVID-19 vaccines and short-term safety : Subgroup analysis from the global COVAD study
  • 2024
  • Ingår i: Journal of Diabetes Investigation. - : John Wiley & Sons. - 2040-1116 .- 2040-1124. ; 15:1, s. 131-138
  • Tidskriftsartikel (refereegranskat)abstract
    • AIMS/INTRODUCTION: Coronavirus disease 2019 (COVID-19) vaccinations have been proven to be generally safe in healthy populations. However, the data on vaccine safety in patients with type 1 diabetes are scarce. This study aimed to evaluate the frequency and severity of short-term (<7-day) adverse vaccination events (AEs) and their risk factors among type 1 diabetes patients. MATERIALS AND METHODS: This study analyzed data from the COVID-19 vaccination in Autoimmune Diseases (COVAD) survey database (May to December 2021; 110 collaborators, 94 countries), comparing <7-day COVID-19 vaccine AE among type 1 diabetes patients and healthy controls (HCs). Descriptive statistics; propensity score matching (1:4) using the variables age, sex and ethnicity; and multivariate analyses were carried out.RESULTS: This study analyzed 5,480 completed survey responses. Of all responses, 5,408 were HCs, 72 were type 1 diabetes patients (43 females, 48.0% white European ancestry) and Pfizer was the most administered vaccine (39%). A total of 4,052 (73.9%) respondents had received two vaccine doses. Patients with type 1 diabetes had a comparable risk of injection site pain, minor and major vaccine AEs, as well as associated hospitalizations to HCs. However, type 1 diabetes patients had a higher risk of severe rashes (3% vs 0.4%, OR 8.0, 95% confidence interval 1.7-36), P = 0.007), although reassuringly, these were rare (n = 2 among type 1 diabetes patients).CONCLUSIONS: COVID-19 vaccination was safe and well tolerated in patients with type 1 diabetes with similar AE profiles compared with HCs, although severe rashes were more common in type 1 diabetes patients.
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22.
  • D'Imperio, Nicolas, et al. (författare)
  • Highly Conjugated Bis(benzo[b]phosphole)-P-oxides : Synthesis and Electrochemical, Optical, and Computational Studies
  • 2023
  • Ingår i: European Journal of Organic Chemistry. - : John Wiley & Sons. - 1434-193X .- 1099-0690. ; 26:4
  • Tidskriftsartikel (refereegranskat)abstract
    • The first examples of a pi-conjugated benzo[b]phosphole P-oxide in which two phosphole P-oxide units are connected by a carbon-carbon double bond are described. The molecules are synthesized as E isomers with respect to the carbon-carbon double bond and exist as stable cis and trans isomers (chiral and meso one respectively) relatively to the two stereogenic P atoms. The optical and electrochemical properties of both isomers have been investigated by experiment and computations.
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23.
  • Ekeberg, Örjan, et al. (författare)
  • Computational Brain Science at CST, CSC, KTH
  • 2016
  • Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
    • Mission and Vision - Computational Brain Science Lab at CST, CSC, KTHThe scientific mission of the Computational Brain Science Lab at CSC is to be at the forefront of mathematical modelling, quantitative analysis and mechanistic understanding of brain function. We perform research on (i) computational modelling of biological brain function and on (ii) developing theory, algorithms and software for building computer systems that can perform brain-like functions. Our research answers scientific questions and develops methods in these fields. We integrate results from our science-driven brain research into our work on brain-like algorithms and likewise use theoretical results about artificial brain-like functions as hypotheses for biological brain research.Our research on biological brain function includes sensory perception (vision, hearing, olfaction, pain), cognition (action selection, memory, learning) and motor control at different levels of biological detail (molecular, cellular, network) and mathematical/functional description. Methods development for investigating biological brain function and its dynamics as well as dysfunction comprises biomechanical simulation engines for locomotion and voice, machine learning methods for analysing functional brain images, craniofacial morphology and neuronal multi-scale simulations. Projects are conducted in close collaborations with Karolinska Institutet and Karolinska Hospital in Sweden as well as other laboratories in Europe, U.S., Japan and India.Our research on brain-like computing concerns methods development for perceptual systems that extract information from sensory signals (images, video and audio), analysis of functional brain images and EEG data, learning for autonomous agents as well as development of computational architectures (both software and hardware) for neural information processing. Our brain-inspired approach to computing also applies more generically to other computer science problems such as pattern recognition, data analysis and intelligent systems. Recent industrial collaborations include analysis of patient brain data with MentisCura and the startup company 13 Lab bought by Facebook.Our long term vision is to contribute to (i) deeper understanding of the computational mechanisms underlying biological brain function and (ii) better theories, methods and algorithms for perceptual and intelligent systems that perform artificial brain-like functions by (iii) performing interdisciplinary and cross-fertilizing research on both biological and artificial brain-like functions. On one hand, biological brains provide existence proofs for guiding our research on artificial perceptual and intelligent systems. On the other hand, applying Richard Feynman’s famous statement ”What I cannot create I do not understand” to brain science implies that we can only claim to fully understand the computational mechanisms underlying biological brain function if we can build and implement corresponding computational mechanisms on a computerized system that performs similar brain-like functions.
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24.
  • Filipović, Marko, 1984- (författare)
  • Characterisation of inputs and outputs of striatal medium spiny neurons in health and disease
  • 2019
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • Striatal medium spiny neurons (MSNs) play a crucial role in various motor and cognitive functions. They are separated into those belonging to the direct pathway (dMSNs) and the indirect pathway (iMSNs) of the basal ganglia, depending on whether they express D1 or D2 type dopamine receptors, respectively. In this thesis I investigated the input processing of both MSN types, the characteristics of dMSN outputs, and the effect that aberrant iMSN activity has on the subthalamic nucleus-globus pallidus externa (STN-GPe) network.In order to verify a previous result from a computational study claiming that dMSNs should receive either more or stronger total input than iMSNs, I performed an analysis of in vivo whole-cell MSN recordings in healthy and dopamine (DA) depleted (6OHDA) anesthetized mice. To test this prediction, I compared subthreshold membrane potential fluctuations and spike-triggered average membrane potentials of the two MSN types. I found that dMSNs in healthy mice exhibited considerably larger fluctuations over a wide frequency range, as well as significantly faster  depolarization towards the spiking threshold than iMSNs. However, these effects were not present in recordings from 6OHDA animals. Together, these findings strongly suggest that dMSNs do  receive stronger total input than iMSNs in healthy condition.I also examined how different concentrations of dopamine affect neural trial-by-trial (or response) variability in a biophysically detailed compartmental model of a direct-pathway MSN.  Some of the sources of trial-by-trial variability include synaptic noise, neural refractory period, and ongoing neural activity. The focus of this study was on the effects of two particular  properties of the synaptic input: correlations of synaptic input rates, and the balance between excitatory and inhibitory inputs (E-I balance). The model demonstrates that dopamine is in  general a significant diminisher of trial-by-trial variability, but that its efficacy depends on the properties of synaptic input. Moreover, input rate correlations and changes in the E-I balance by themselves also proved to have a marked impact on the response variability.Finally, I investigated the beta-band phase properties of the STN-GPe network, known for its exaggerated beta-band oscillations during Parkinson’s disease (PD). The current state-of-the-art  computational model of the network can replicate both transient and persistent beta oscillations, but fails to capture the beta-band phase alignment between the two nuclei as seen in human  recordings. This was particularly evident during simulations of the PD condition, where STN or GPe were receiving additional stimulation in order to induce pathological levels of beta-band  activity. Here I show that by manipulating the percentage of the neurons in either population that receives stimulation it is possible to increase STN-GPe phase difference heterogeneity.  Furthermore, a similar effect can be achieved by adjusting synaptic transmission delays between the two populations. Quantifying the difference between human recordings and network  simulations, I provide the set of parameters for which the model produces the greatest correspondence with experimental results.
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25.
  • Filipovic, Marko, et al. (författare)
  • Direct pathway neurons in mouse dorsolateral striatum in vivo receive stronger synaptic input than indirect pathway neurons
  • 2019
  • Ingår i: Journal of Neurophysiology. - : AMER PHYSIOLOGICAL SOC. - 0022-3077 .- 1522-1598. ; 122:6, s. 2294-2303
  • Tidskriftsartikel (refereegranskat)abstract
    • Striatal projection neurons, the medium spiny neurons (MSNs), play a crucial role in various motor and cognitive functions. MSNs express either D1- or D2-type dopamine receptors and initiate the direct-pathway (dMSNs) or indirect pathways (iMSNs) of the basal ganglia, respectively. dMSNs have been shown to receive more inhibition than iMSNs from intrastriatal sources. Based on these findings, computational modeling of the suiatal network has predicted that under healthy conditions dMSNs should receive more total input than iMSNs. To test this prediction, we analyzed in vivo whole cell recordings from dMSNs and iMSNs in healthy and dopamine-depleted (60HDA) anaesthetized mice. By comparing their membrane potential fluctuations, we found that dMSNs exhibited considerably larger membrane potential fluctuations over a wide frequency range. Furthermore, by comparing the spike-triggered average membrane potentials. we found that dMSNs depolarized toward the spike threshold significantly faster than iMSNs did. Together, these findings (in particular the STA analysis) corroborate the theoretical prediction that direct-pathway MSNs receive stronger total input than indirect-pathway neurons. Finally, we found that dopamine-depleted mice exhibited no difference between the membrane potential fluctuations of dMSNs and iMSNs. These data provide new insights into the question of how the lack of dopamine may lead to behavioral deficits associated with Parkinson's disease. NEW & NOTEWORTHY The direct and indirect pathways of the basal ganglia originate from the D1- and D2-type dopamine receptor expressing medium spiny neurons (dMSNs and iMSNs). Theoretical results have predicted that dMSNs should receive stronger synaptic input than iMSNs. Using in vivo intracellular membrane potential data, we provide evidence that dMSNs indeed receive stronger input than iMSNs, as has been predicted by the computational model.
  •  
26.
  • Froriep, Ulrich P, et al. (författare)
  • Altered theta coupling between medial entorhinal cortex and dentate gyrus in temporal lobe epilepsy
  • 2012
  • Ingår i: Epilepsia. - : Wiley. - 0013-9580 .- 1528-1167. ; 53:11, s. 1937-1947
  • Tidskriftsartikel (refereegranskat)abstract
    • Purpose: Temporal lobe epilepsy is often accompanied by neuron loss and rewiring in the hippocampus. We hypothesized that the interaction of subnetworks of the entorhinalhippocampal loop between epileptic events should show significant signatures of these pathologic changes.Methods: We combined simultaneous recording of local field potentials in entorhinal cortex (EC) and dentate gyrus (DG) in freely behaving kainate-injected mice with histologic analyses and computational modeling.Key Findings: In healthy mice, theta band activity was synchronized between EC and DG. In contrast, in epileptic mice, theta activity in the EC was delayed with respect to the DG. A computational neural mass model suggests that hippocampal cell loss imbalances the coupling of subnetworks, introducing the shift.Significance: We show that pathologic dynamics in epilepsy encompass ongoing activity in the entorhinal-hippocampal loop beyond acute epileptiform activity. This predominantly affects theta band activity, which links this shift in entorhinal-hippocampal interaction to behavioral aspects in epilepsy.
  •  
27.
  • Grah, Gunnar, et al. (författare)
  • Wettstreit der Metaphern
  • 2014
  • Ingår i: Geist und Gehirn. - 1618-8519. ; :7, s. 60-65
  • Forskningsöversikt (populärvet., debatt m.m.)
  •  
28.
  • Grah, Gunnar, et al. (författare)
  • Zittern in zahlen
  • 2013
  • Ingår i: Geist und Gehirn. - 1618-8519. ; :5, s. 68-73
  • Forskningsöversikt (populärvet., debatt m.m.)
  •  
29.
  • Grangeray-Vilmint, Anais, et al. (författare)
  • Short-Term Plasticity Combines with Excitation-Inhibition Balance to Expand Cerebellar Purkinje Cell Dynamic Range
  • 2018
  • Ingår i: Journal of Neuroscience. - : SOC NEUROSCIENCE. - 0270-6474 .- 1529-2401. ; 38:22, s. 5153-5167
  • Tidskriftsartikel (refereegranskat)abstract
    • The balance between excitation (E) and inhibition (I) in neuronal networks controls the firing rate of principal cells through simple network organization, such as feedforward inhibitory circuits. Here, we demonstrate in male mice, that at the granule cell (GrC)molecular layer interneuron (MLI)-Purkinje cell (PC) pathway of the cerebellar cortex, E/I balance is dynamically controlled by short-term dynamics during bursts of stimuli, shaping cerebellar output. Using a combination of electrophysiological recordings, optogenetic stimulation, and modeling, we describe the wide range of bidirectional changes in PC discharge triggered by GrC bursts, from robust excitation to complete inhibition. At high frequency (200 Hz), increasing the number of pulses in a burst (from 3 to 7) can switch a net inhibition of PC to a net excitation. Measurements of EPSCs and IPSCs during bursts and modeling showed that this feature can be explained by the interplay between short-term dynamics of the GrC-MLI-PC pathway and E/I balance impinging on PC. Our findings demonstrate that PC firing rate is highly sensitive to the duration of GrC bursts, which may define a temporal-to-rate code transformation in the cerebellar cortex.
  •  
30.
  • Green, Joshua P., et al. (författare)
  • Effect of Arsenic Coordination State on the Structure, Aromaticity, and Optical Properties of Dithieno[3,2-b:2 ',3 '-d]arsoles
  • 2019
  • Ingår i: European Journal of Inorganic Chemistry. - : Wiley. - 1434-1948 .- 1099-1948 .- 1099-0682. ; :11-12, s. 1539-1543
  • Tidskriftsartikel (refereegranskat)abstract
    • A silylated derivative of 4-phenyl-dithieno[3,2-b:2 ',3 '-d]arsole (DTAs) was synthesized, and the effect of coordinating of DTAs compounds to Pd on their structural and optical properties was investigated. Coordination of the As to Pd was found to increase the structural aromaticity of the ring system as measured by the harmonic oscillator measure of heterocyclic electron delocalization (HOMHED), and the pyramidalization of the As atoms was also found to show a good correlation with the HOMHED values. However, coordination had a more subtle impact on the optical properties than seen for phosphorus-containing analogues as the metal-ligand interactions were weaker.
  •  
31.
  • Green, Joshua P., et al. (författare)
  • Golden Age of Fluorenylidene Phosphaalkenes-Synthesis, Structures, and Optical Properties of Heteroaromatic Derivatives and Their Gold Complexes
  • 2020
  • Ingår i: Journal of Organic Chemistry. - : American Chemical Society (ACS). - 0022-3263 .- 1520-6904. ; 85:22, s. 14619-14626
  • Tidskriftsartikel (refereegranskat)abstract
    • The substitution of 2,7-dibromo-9-fluorenyl phosphaalkenes with heteroaromatic substituents (bithiophene, benzothiophene, pyridine) offers access to interesting push-pull dye molecules. Steric shielding due to the bulky P-substituent gives marked different reactivities at the 2- and 7-positions, allowing the synthesis of mixed/asymmetric derivatives. Further functionalization via gold(I) coordination was demonstrated and increased the acceptor character, concomitant with a red-shifted absorption.
  •  
32.
  • Guo, Lihao, et al. (författare)
  • Role of interneuron subtypes in controlling trial-by-trial output variability in the neocortex
  • 2023
  • Ingår i: Communications Biology. - : Springer Nature. - 2399-3642. ; 6:1
  • Tidskriftsartikel (refereegranskat)abstract
    • Trial-by-trial variability is a ubiquitous property of neuronal activity in vivo which shapes the stimulus response. Computational models have revealed how local network structure and feedforward inputs shape the trial-by-trial variability. However, the role of input statistics and different interneuron subtypes in this process is less understood. To address this, we investigate the dynamics of stimulus response in a cortical microcircuit model with one excitatory and three inhibitory interneuron populations (PV, SST, VIP). Our findings demonstrate that the balance of inputs to different neuron populations and input covariances are the primary determinants of output trial-by-trial variability. The effect of input covariances is contingent on the input balances. In general, the network exhibits smaller output trial-by-trial variability in a PV-dominated regime than in an SST-dominated regime. Importantly, our work reveals mechanisms by which output trial-by-trial variability can be controlled in a context, state, and task-dependent manner.
  •  
33.
  • Gupta, Arvind Kumar, et al. (författare)
  • Alkynyl Coinage Metal Clusters and Complexes-Syntheses, Structures, and Strategies
  • 2018
  • Ingår i: Chemistry - A European Journal. - : Wiley-VCH Verlagsgesellschaft. - 0947-6539 .- 1521-3765. ; 24:30, s. 7536-
  • Tidskriftsartikel (refereegranskat)abstract
    • In this Concept we discuss how the chemistry of coinage metal complexes based on alkynyl ligands has developed over the past decades. The rich coordination of alkynyl, that exhibit both (1) (end-on) and (2) (side on) modes, includes non-bridged systems, as well as bridging of up to four (or six) metal centres. Resulting metal clusters often exhibit highly regular structures and typical coordination motifs forming fascinating assemblies exploiting this versatile coordination. Metallophilic interactions are often an important driving force for the formation of large clusters. In addition, the use of co-ligands as well the possibility to encapsulate counter ions greatly increases the chemical and structural diversity. Herein we attempt to summarize and highlight design principles towards multinuclear homo and hetero-bi-metallic coinage metal clusters of alkynyl ligands.
  •  
34.
  • Gupta, Arvind Kumar, et al. (författare)
  • Facile synthesis of silver alkynide cluster and coordination polymers using picolinic acid as a co-ligand
  • 2019
  • Ingår i: Dalton Transactions. - : ROYAL SOC CHEMISTRY. - 1477-9226 .- 1477-9234. ; 48:44, s. 16518-16524
  • Tidskriftsartikel (refereegranskat)abstract
    • We describe five 1D-coordination polymers and two discrete silver clusters consisting of alkynides and picolinic carboxylates as co-ligands. In some cases, DMSO or EtOH further solvated the structural motifs. Utilising the sterically demanding tri-isopropylsilyl acetylene afforded a tridecanuclear cluster that possessed an unprecedented core with a silver center surrounded by six octahedrally arranged silver atoms.
  •  
35.
  • Gupta, Arvind Kumar, et al. (författare)
  • Rearrangement and redistribution reaction of Ph2PCH2TMS with PhAsCl2 or AsCl3
  • 2019
  • Ingår i: Phosphorus Sulfur and Silicon and the Related Elements. - : TAYLOR & FRANCIS LTD. - 1042-6507 .- 1563-5325. ; 194:10, s. 967-971
  • Tidskriftsartikel (refereegranskat)abstract
    • The attempted synthesis of bis(diphenylphosphinomethyl) phenylarsane and tris(diphenylphosphinomethyl) arsane through condensation of chloro arsanes and diphenyl (trimethylsilylmethyl) phosphane yielded a number of side products originating from migratory and redox-reactions in addition to the targeted ligands. An unexpected, 1,3,4-phosphadiarssolan-1-ium salt was obtained and crystallographically characterized as an A-shaped chlorido adduct. [GRAPHICS] .
  •  
36.
  • Gupta, Arvind Kumar, et al. (författare)
  • Rich Coordination Chemistry of pi-Acceptor Dibenzoarsole Ligands
  • 2017
  • Ingår i: Inorganic Chemistry. - : American Chemical Society (ACS). - 0020-1669 .- 1520-510X. ; 56:8, s. 4504-4511
  • Tidskriftsartikel (refereegranskat)abstract
    • A series of dibenzoarsole (also known as 9-arsafluorene) derivatives have been prepared, and their coordination chemistry has been investigated. The different ligand topology and the arsenic substituents govern the reactivity of the ligands. We report various crystal structures of palladium and platinum complexes derived from this family of ligands. The biphenyl backbone of the bridged bidentate ligands allows very flexible coordination. We have also studied the application of an allylic Pd complex in nucleophilic substitution reactions, revealing that the benzoarsole substituent is susceptible to metal insertion.
  •  
37.
  • Gupta, Arvind Kumar, et al. (författare)
  • Serendipitous and Targeted Synthesis of High Nuclearity Clusters : Carbonate and Oxalate Encapsulating Silver Alkynides
  • 2020
  • Ingår i: Crystal Growth & Design. - : American Chemical Society (ACS). - 1528-7483 .- 1528-7505. ; 20:7, s. 4232-4237
  • Tidskriftsartikel (refereegranskat)abstract
    • Silver coordination compounds of the [Ag3L2] (where L = Bu-t-C=C) family having perchlorate counterions exhibit template-driven self-assembly of the common square pyramidal building block. This behavior is similar to previously described observations; however, important differences arise from counterion-silver interactions. Penta- and hexameric clusters encapsulating chloride and oxalate, respectively, were crystallographically characterized. A high nuclearity cluster [(CO3)(3)(H2O)subset of Ag38L20](12+) was formed upon extended exposure to an ambient atmosphere by trapping three carbonates and one water molecule.
  •  
38.
  • Gupta, Arvind Kumar, et al. (författare)
  • Solvent and Counter-Ion Induced Coordination Environment Changes Towards Ag-I Coordination Polymers
  • 2019
  • Ingår i: European Journal of Inorganic Chemistry. - : WILEY-V C H VERLAG GMBH. - 1434-1948 .- 1099-1948 .- 1099-0682. ; 2019:33, s. 3740-3744
  • Tidskriftsartikel (refereegranskat)abstract
    • A series of silver coordination polymers based on the 9,9 '-bis(4,5-diazafluorene) (BDF-H-2) ligand is presented. The choice of counterions and reaction conditions dictate the observed topology on the final systems by influencing the silver coordination environment. Coordination modes, flexibility of the ligand and extended pi-pi stacking interactions have allowed the preparation and crystallographic characterisation of one 1D- and three 2D-coordination polymers: 1D-[Ag(BDF-H-2)(DMSO)](n)(X)(n) (where X = OTf- and ClO4-); 1D-[Ag-2(BDF-H-2) m(1)-(TfO)(2),m(2)-(TfO)(2)](n)(TfO)(n), and 2D-[Ag-2(BDF-H-2)(3)](n)(PF6)(2n).
  •  
39.
  • Gupta, Arvind Kumar, et al. (författare)
  • The Self-Assembly of [{Ag-3(C (CBu)-Bu-t)(2)}(n)](n+) Building Units into a Template-Free Cuboctahedron and Anion-Encapsulating Silver Cages
  • 2019
  • Ingår i: Inorganic Chemistry. - : AMER CHEMICAL SOC. - 0020-1669 .- 1520-510X. ; 58:23, s. 16236-16240
  • Tidskriftsartikel (refereegranskat)abstract
    • We describe the controlled synthesis of silver acetylide clusters based on a simple polymeric [Ag3L2](+) (L = -C (CBu)-Bu-t) building block. A linear one-dimensional polymeric structure shows alternating pyramidal motifs and is the basic repeating unit forming discrete molecular cages (pentamers [X subset of Ag15L10](4+) and hexamers [PF6 subset of Ag18L12](5+)) obtained by incorporating suitable templates. These motifs and a rare template-free cuboctahedral [Ag12L8](4+) cluster (tetramer) were crystallographically characterized.
  •  
40.
  • Hahn, Gerald, et al. (författare)
  • Communication through resonance in spiking neuronal networks
  • 2014
  • Ingår i: PloS Computational Biology. - : Public Library of Science (PLoS). - 1553-734X .- 1553-7358. ; 10:8
  • Tidskriftsartikel (refereegranskat)abstract
    • The cortex processes stimuli through a distributed network of specialized brain areas. This processing requires mechanisms that can route neuronal activity across weakly connected cortical regions. Routing models proposed thus far are either limited to propagation of spiking activity across strongly connected networks or require distinct mechanisms that create local oscillations and establish their coherence between distant cortical areas. Here, we propose a novel mechanism which explains how synchronous spiking activity propagates across weakly connected brain areas supported by oscillations. In our model, oscillatory activity unleashes network resonance that amplifies feeble synchronous signals and promotes their propagation along weak connections ("communication through resonance''). The emergence of coherent oscillations is a natural consequence of synchronous activity propagation and therefore the assumption of different mechanisms that create oscillations and provide coherence is not necessary. Moreover, the phase-locking of oscillations is a side effect of communication rather than its requirement. Finally, we show how the state of ongoing activity could affect the communication through resonance and propose that modulations of the ongoing activity state could influence information processing in distributed cortical networks.
  •  
41.
  • Hahn, Gerald, et al. (författare)
  • Portraits of communication in neuronal networks
  • 2019
  • Ingår i: Nature Reviews Neuroscience. - : NATURE PUBLISHING GROUP. - 1471-003X .- 1471-0048. ; 20:2, s. 117-127
  • Forskningsöversikt (refereegranskat)abstract
    • The brain is organized as a network of highly specialized networks of spiking neurons. To exploit such a modular architecture for computation, the brain has to be able to regulate the flow of spiking activity between these specialized networks. In this Opinion article, we review various prominent mechanisms that may underlie communication between neuronal networks. We show that communication between neuronal networks can be understood as trajectories in a two-dimensional state space, spanned by the properties of the input. Thus, we propose a common framework to understand neuronal communication mediated by seemingly different mechanisms. We also suggest that the nesting of slow (for example, alpha-band and theta-band) oscillations and fast (gamma-band) oscillations can serve as an important control mechanism that allows or prevents spiking signals to be routed between specific networks. We argue that slow oscillations can modulate the time required to establish network resonance or entrainment and, thereby, regulate communication between neuronal networks.
  •  
42.
  • Hahn, Gerald, et al. (författare)
  • Rate and oscillatory switching dynamics of a multilayer visual microcircuit model
  • 2022
  • Ingår i: eLIFE. - : eLife Sciences Publications, Ltd. - 2050-084X. ; 11
  • Tidskriftsartikel (refereegranskat)abstract
    • The neocortex is organized around layered microcircuits consisting of a variety of excitatory and inhibitory neuronal types which perform rate- and oscillation-based computations. Using modeling, we show that both superficial and deep layers of the primary mouse visual cortex implement two ultrasensitive and bistable switches built on mutual inhibitory connectivity motives between somatostatin, parvalbumin, and vasoactive intestinal polypeptide cells. The switches toggle pyramidal neurons between high and low firing rate states that are synchronized across layers through translaminar connectivity. Moreover, inhibited and disinhibited states are characterized by low- and high-frequency oscillations, respectively, with layer-specific differences in frequency and power which show asymmetric changes during state transitions. These findings are consistent with a number of experimental observations and embed firing rate together with oscillatory changes within a switch interpretation of the microcircuit.
  •  
43.
  • Hahn, Gerald, et al. (författare)
  • Spontaneous cortical activity is transiently poised close to criticality
  • 2017
  • Ingår i: PloS Computational Biology. - : Public Library of Science. - 1553-734X .- 1553-7358. ; 13:5
  • Tidskriftsartikel (refereegranskat)abstract
    • Brain activity displays a large repertoire of dynamics across the sleep-wake cycle and even during anesthesia. It was suggested that criticality could serve as a unifying principle underlying the diversity of dynamics. This view has been supported by the observation of spontaneous bursts of cortical activity with scale-invariant sizes and durations, known as neuronal avalanches, in recordings of mesoscopic cortical signals. However, the existence of neuronal avalanches in spiking activity has been equivocal with studies reporting both its presence and absence. Here, we show that signs of criticality in spiking activity can change between synchronized and desynchronized cortical states. We analyzed the spontaneous activity in the primary visual cortex of the anesthetized cat and the awake monkey, and found that neuronal avalanches and thermodynamic indicators of criticality strongly depend on collective synchrony among neurons, LFP fluctuations, and behavioral state. We found that synchronized states are associated to criticality, large dynamical repertoire and prolonged epochs of eye closure, while desynchronized states are associated to sub-criticality, reduced dynamical repertoire, and eyes open conditions. Our results show that criticality in cortical dynamics is not stationary, but fluctuates during anesthesia and between different vigilance states.
  •  
44.
  • Heining, Katharina, et al. (författare)
  • Bursts with High and Low Load of Epileptiform Spikes Show Contex-Dependent Correlations in Epileptic Mice
  • 2019
  • Ingår i: eNeuro. - : SOC NEUROSCIENCE. - 2373-2822. ; 6:5
  • Tidskriftsartikel (refereegranskat)abstract
    • Hypersynchronous network activity is the defining hallmark of epilepsy and manifests in a wide spectrum of phenomena, of which electrographic activity during seizures is only one extreme. The aim of this study was to differentiate between different types of epileptiform activity (EA) patterns and investigate their temporal succession and interactions. We analyzed local field potentials (LFPs) from freely behaving male mice that had received an intrahippocampal kainate injection to model mesial temporal lobe epilepsy (MTLE). Epileptiform spikes occurred in distinct bursts. Using machine learning, we derived a scale reflecting the spike load of bursts and three main burst categories that we labeled high-load, medium-load, and low-load bursts. We found that bursts of these categories were non-randomly distributed in time. High-load bursts formed clusters and were typically surrounded by transition phases with increased rates of medium-load and low-load bursts. In apparent contradiction to this, increased rates of low-load bursts were also associated with longer background phases, i.e., periods lacking high-load bursting. Furthermore, the rate of low-load bursts was more strongly correlated with the duration of background phases than the overall rate of epileptiform spikes. Our findings are consistent with the hypothesis that low-level EA could promote network stability but could also participate in transitions towards major epileptiform events, depending on the current state of the network.
  •  
45.
  • Helson, Pascal, et al. (författare)
  • Cortex-wide topography of 1/f-exponent in Parkinson's disease
  • 2023
  • Ingår i: npj Parkinson's Disease. - : Springer Nature. - 2373-8057. ; 9:1
  • Tidskriftsartikel (refereegranskat)abstract
    • Parkinson's disease (PD) is a progressive and debilitating brain disorder. Besides the characteristic movement-related symptoms, the disease also causes decline in sensory and cognitive processing. The extent of symptoms and brain-wide projections of neuromodulators such as dopamine suggest that many brain regions are simultaneously affected in PD. To characterise brain-wide disease-related changes in neuronal function, we analysed resting state magnetoencephalogram (MEG) from two groups: PD patients and healthy controls. Besides standard spectral analysis, we quantified the aperiodic components (& kappa;, & lambda;) of the neural activity by fitting a power law & kappa;/f(& lambda;) - f is the frequency, & kappa; and & lambda; are the fitting parameters-to the MEG power spectrum and studied its relationship with age and Unified Parkinson's Disease Rating Scale (UPDRS). Consistent with previous results, the most significant spectral changes were observed in the high theta/low-alpha band (7-10 Hz) in all brain regions. Furthermore, analysis of the aperiodic part of the spectrum showed that in all but frontal regions & lambda; was significantly larger in PD patients than in control subjects. Our results indicate that PD is associated with significant changes in aperiodic activity across the whole neocortex. Surprisingly, even early sensory areas showed a significantly larger & lambda; in patients than in healthy controls. Moreover, & lambda; was not affected by the Levodopa medication. Finally, & lambda; was positively correlated with patient age but not with UPDRS-III. Because & lambda; is closely associated with excitation-inhibition balance, our results propose new hypotheses about neural correlates of PD in cortical networks.
  •  
46.
  • Hunger, Lars, et al. (författare)
  • Abundance Compensates Kinetics : Similar Effect of Dopamine Signals on D1 and D2 Receptor Populations
  • 2020
  • Ingår i: Journal of Neuroscience. - : Society for Neuroscience. - 0270-6474 .- 1529-2401. ; 40:14, s. 2868-2881
  • Tidskriftsartikel (refereegranskat)abstract
    • The neuromodulator dopamine plays a key role in motivation, reward-related learning, and normal motor function. The different affinity of striatal D1 and D2 dopamine receptor types has been argued to constrain the D1 and D2 signaling pathways to phasic and tonic dopamine signals, respectively. However, this view assumes that dopamine receptor kinetics are instantaneous so that the time courses of changes in dopamine concentration and changes in receptor occupation are basically identical. Here we developed a neurochemical model of dopamine receptor binding taking into account the different kinetics and abundance of D1 and D2 receptors in the striatum. Testing a large range of behaviorally-relevant dopamine signals, we found that the D1 and D2 dopamine receptor populations responded very similarly to tonic and phasic dopamine signals. Furthermore, because of slow unbinding rates, both receptor populations integrated dopamine signals over a timescale of minutes. Our model provides a description of how physiological dopamine signals translate into changes in dopamine receptor occupation in the striatum, and explains why dopamine ramps are an effective signal to occupy dopamine receptors. Overall, our model points to the importance of taking into account receptor kinetics for functional considerations of dopamine signaling.
  •  
47.
  • Jha, Paridhi, et al. (författare)
  • Developing and validating a tool for assessing the confidence in the competence of midwifery tutors in India on WHO core competency domains
  • 2024
  • Ingår i: PLOS Global Public Health. - 2767-3375. ; 4
  • Tidskriftsartikel (refereegranskat)abstract
    • Negligible quantitative research evidence exists on standardisation and psychometric validation of questionnaires that measure midwifery educators’ confidence in their competence. This study developed a self-assessment of confidence in competence questionnaire in India based on the WHO Midwifery Educator Core Competencies (2014) with an aim to develop and validate a self-assessment tool measuring midwifery tutors’ confidence in competence in imparting quality midwifery education. The questionnaire was developed as part of a multicentre study to identify confident midwifery tutors for further training as educators, supporting India’s rollout of professional midwives. The questionnaire underwent rigorous psychometric testing among 2016 midwifery tutors in India. Following exploratory Principal Component Analyses (PCA), the nine core competencies outlined in the WHO document were analysed separately. The results indicate that the questionnaire is psychometrically valid, with an internal consistency range of 0.81–0.93 for the nine domains. This robust testing process ensures the reliability and validity of the questionnaire. The self-assessment questionnaire can potentially be a valuable tool in India and other high-, middle-, and low-income countries. From a programmatic perspective, it can help identify key gaps and prioritise training needs, particularly in low-resource settings, so that limited resources are best utilised to fill the most prominent gaps. Furthermore, it can provide a universal platform for comparing data from different settings, facilitating global collaboration and learning in midwifery education.
  •  
48.
  • Johnson, Catherine, et al. (författare)
  • Ferrous and ferric complexes with cyclometalating N-heterocyclic carbene ligands : a case of dual emission revisited
  • 2023
  • Ingår i: Chemical Science. - : Royal Society of Chemistry. - 2041-6520 .- 2041-6539. ; 14:37, s. 10129-10139
  • Tidskriftsartikel (refereegranskat)abstract
    • Iron N-heterocyclic carbene (FeNHC) complexes with long-lived charge transfer states are emerging as a promising class of photoactive materials. We have synthesized [Fe-II(ImP)(2)] (ImP = bis(2,6-bis(3-methylimidazol-2-ylidene-1-yl)phenylene)) that combines carbene ligands with cyclometalation for additionally improved ligand field strength. The 9 ps lifetime of its (MLCT)-M-3 (metal-to-ligand charge transfer) state however reveals no benefit from cyclometalation compared to Fe(II) complexes with NHC/pyridine or pure NHC ligand sets. In acetonitrile solution, the Fe(II) complex forms a photoproduct that features emission characteristics (450 nm, 5.1 ns) that were previously attributed to a higher ((MLCT)-M-2) state of its Fe(III) analogue [Fe-III(ImP)(2)](+), which led to a claim of dual (MLCT and LMCT) emission. Revisiting the photophysics of [Fe-III(ImP)(2)](+), we confirmed however that higher ((MLCT)-M-2) states of [Fe-III(ImP)(2)](+) are short-lived (<10 ps) and therefore, in contrast to the previous interpretation, cannot give rise to emission on the nanosecond timescale. Accordingly, pristine [Fe-III(ImP)(2)](+) prepared by us only shows red emission from its lower (LMCT)-L-2 state (740 nm, 240 ps). The long-lived, higher energy emission previously reported for [Fe-III(ImP)(2)](+) is instead attributed to an impurity, most probably a photoproduct of the Fe(II) precursor. The previously reported emission quenching on the nanosecond time scale hence does not support any excited state reactivity of [Fe-III(ImP)(2)](+) itself.
  •  
49.
  • Josyula, Tejaswi, et al. (författare)
  • Fundamentals and Applications of Surface Wetting
  • 2024
  • Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 40:16, s. 8293-8326
  • Forskningsöversikt (refereegranskat)abstract
    • In an era defined by an insatiable thirst for sustainable energy solutions, responsible water management, and cutting-edge lab-on-a-chip diagnostics, surface wettability plays a pivotal role in these fields. The seamless integration of fundamental research and the following demonstration of applications on these groundbreaking technologies hinges on manipulating fluid through surface wettability, significantly optimizing performance, enhancing efficiency, and advancing overall sustainability. This Review explores the behavior of liquids when they engage with engineered surfaces, delving into the far-reaching implications of these interactions in various applications. Specifically, we explore surface wetting, dissecting it into three distinctive facets. First, we delve into the fundamental principles that underpin surface wetting. Next, we navigate the intricate liquid-surface interactions, unraveling the complex interplay of various fluid dynamics, as well as heat- and mass-transport mechanisms. Finally, we report on the practical realm, where we scrutinize the myriad applications of these principles in everyday processes and real-world scenarios.
  •  
50.
  • Kaur-Kahlon, Gurpreet, et al. (författare)
  • Response of a coastal tropical pelagic microbial community to changed salinity and temperature
  • 2016
  • Ingår i: Aquatic Microbial Ecology. - : Inter-Research Science Center. - 0948-3055 .- 1616-1564. ; 77:1, s. 37-50
  • Tidskriftsartikel (refereegranskat)abstract
    • Studies on the responses of tropical microbial communities to changing hydrographic conditions are poorly represented. We present here the results from a mesocosm experiment conducted in coastal southwestern India to investigate how changes in temperature and salinity may affect a coastal tropical microbial community. The onset of algal and bacterial blooms, maximum production and biomass, and the interrelationship between phytoplankton and bacteria were studied in replicated mesocosms. The treatments were set up to feature ambient conditions (28°C, 35 PSU), hyposalinity (31 PSU), warming (31°C), and a double manipulation treatment with warming and hyposalinity (31°C, 31 PSU). The hyposaline treatment had the most considerable influence, manifested as significantly lower primary production, and the most dissimilar microphytoplankton species community. The increased temperature acted as a catalyst in the double manipulation treatment, and higher primary production was maintained. We investigated the dynamics of the microbial community with a structural equation model and found a significant interrelationship between phytoplankton biomass and bacterial abundance. Using this methodology, it became evident that temperature and salinity changes, individually and together, mediate direct and indirect effects that influence different compartments of the microbial loop. In the face of climate change, we suggest that in relatively nutrient-replete tropical coastal zones, salinity and temperature changes will affect nutrient assimilation, with subsequent significant effects on the quantity of microbial biomass and production.
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