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Alain Destexhe – One of the best experts on this subject based on the ideXlab platform.

  • Inhibitory “noise”.
    Frontiers in Cellular Neuroscience, 2010
    Co-Authors: Alain Destexhe
    Abstract:

    Cortical neurons in vivo may operate in high-Conductance states, in which the major part of the neuron‘s input Conductance is due to synaptic activity, sometimes several-fold larger than the resting Conductance. We examine here the contribution of inhibition in such high-Conductance states. At the level of the absolute Conductance values, several studies have shown that cortical neurons in vivo are characterized by strong inhibitory Conductances. However, Conductances are balanced and spiking activity is mostly determined by fluctuations, but not much is known about excitatory and inhibitory contributions to these fluctuations. Models and dynamic-clamp experiments show that, during high-Conductance states, spikes are mainly determined by fluctuations of inhibition, or by inhibitory “noise”. This stands in contrast to low-Conductance states, in which excitatory Conductances determine spiking activity. To determine these contributions from experimental data, maximum likelihood methods can be designed and applied to intracellular recordings in vivo. Such methods indicate that action potentials are indeed mostly correlated with inhibitory fluctuations in awake animals. These results argue for a determinant role for inhibitory fluctuations in evoking spikes, and do not support feed-forward modes of processing, for which opposite patterns are predicted.

  • inhibition determines membrane potential dynamics and controls action potential generation in awake and sleeping cat cortex
    The Journal of Neuroscience, 2007
    Co-Authors: Michelle Rudolph, Martin Pospischil, Igor Timofeev, Alain Destexhe
    Abstract:

    Intracellular recordings of cortical neurons in awake cat and monkey show a depolarized state, sustained firing, and intense subthreshold synaptic activity. It is not known what Conductance dynamics underlie such activity and how neurons process information in such highly stochastic states. Here, we combine intracellular recordings in awake and naturally sleeping cats with computational models to investigate subthreshold dynamics of Conductances and how Conductance dynamics determine spiking activity. We show that during both wakefulness and the “up-states” of natural slow-wave sleep, membrane-potential activity stems from a diversity of combinations of excitatory and inhibitory synaptic Conductances, with dominant inhibition in most of the cases. Inhibition also provides the largest contribution to membrane potential fluctuations. Computational models predict that in such inhibition-dominant states, spikes are preferentially evoked by a drop of inhibitory Conductance, and that its signature is a transient drop of membrane Conductance before the spike. This pattern of Conductance change is indeed observed in estimates of spike-triggered averages of synaptic Conductances during wakefulness and slow-wave sleep up states. These results show that activated states are defined by diverse combinations of excitatory and inhibitory Conductances with pronounced inhibition, and that the dynamics of inhibition is particularly effective on spiking, suggesting an important role for inhibitory processes in both conscious and unconscious cortical states.

  • calculating event triggered average synaptic Conductances from the membrane potential
    Journal of Neurophysiology, 2007
    Co-Authors: Martin Pospischil, Zuzanna Piwkowska, Michelle Rudolph, Thierry Bal, Alain Destexhe
    Abstract:

    The optimal patterns of synaptic Conductances for spike generation in central neurons is a subject of considerable interest. Ideally such Conductance time courses should be extracted from membrane …

Ramesh C. Sharma – One of the best experts on this subject based on the ideXlab platform.

  • Conductance Studies of Tetrabutylammonium Bromide, Sodium Bromide, and Sodium Tetraphenylborate in 2-Butoxyethanol (1) + Water (2) Mixtures at (298.15, 303.15, 308.15, and 313.15) K
    Journal of Chemical & Engineering Data, 2012
    Co-Authors: Binod Sharma, Ramesh C. Sharma
    Abstract:

    Electrical Conductances of solutions of tetrabutylammonium bromide (Bu4NBr), sodium bromide (NaBr), and sodium tetraphenylborate (NaBPh4) in 2-butoxyethanol (1) + water (2) mixture with 0.017, 0.037, 0.061, 0.092, and 0.132 mole fraction of 2-butoxyethanol have been reported at (298.15, 303.15, 308.15, and 313.15) K. The experimental values of electrical Conductances are analyzed using the 1978 Fuoss Conductanceconcentration equation to obtain the values of limiting molar Conductance (Λ0), ionic association constant (KA), and the association diameter (R). The values of KA and R obtained for these three salts, namely, tetrabutylammonium bromide, sodium bromide, and sodium tetraphenylborate, suggests a weak electrostatic ion–solvent interaction and that they exist as free ions in all the solvent compositions and the temperature range covered in this study. The Walden products of these salts deviate from ideal behavior with varying temperature and solvent composition.

  • Conductance studies of tetrabutylammonium bromide sodium bromide and sodium tetraphenylborate in 2 butoxyethanol 1 water 2 mixtures at 298 15 303 15 308 15 and 313 15 k
    Journal of Chemical & Engineering Data, 2012
    Co-Authors: Binod Sharma, Ramesh C. Sharma
    Abstract:

    Electrical Conductances of solutions of tetrabutylammonium bromide (Bu4NBr), sodium bromide (NaBr), and sodium tetraphenylborate (NaBPh4) in 2-butoxyethanol (1) + water (2) mixture with 0.017, 0.037, 0.061, 0.092, and 0.132 mole fraction of 2-butoxyethanol have been reported at (298.15, 303.15, 308.15, and 313.15) K. The experimental values of electrical Conductances are analyzed using the 1978 Fuoss Conductanceconcentration equation to obtain the values of limiting molar Conductance (Λ0), ionic association constant (KA), and the association diameter (R). The values of KA and R obtained for these three salts, namely, tetrabutylammonium bromide, sodium bromide, and sodium tetraphenylborate, suggests a weak electrostatic ion–solvent interaction and that they exist as free ions in all the solvent compositions and the temperature range covered in this study. The Walden products of these salts deviate from ideal behavior with varying temperature and solvent composition.

Binod Sharma – One of the best experts on this subject based on the ideXlab platform.

  • Conductance Studies of Tetrabutylammonium Bromide, Sodium Bromide, and Sodium Tetraphenylborate in 2-Butoxyethanol (1) + Water (2) Mixtures at (298.15, 303.15, 308.15, and 313.15) K
    Journal of Chemical & Engineering Data, 2012
    Co-Authors: Binod Sharma, Ramesh C. Sharma
    Abstract:

    Electrical Conductances of solutions of tetrabutylammonium bromide (Bu4NBr), sodium bromide (NaBr), and sodium tetraphenylborate (NaBPh4) in 2-butoxyethanol (1) + water (2) mixture with 0.017, 0.037, 0.061, 0.092, and 0.132 mole fraction of 2-butoxyethanol have been reported at (298.15, 303.15, 308.15, and 313.15) K. The experimental values of electrical Conductances are analyzed using the 1978 Fuoss Conductance–concentration equation to obtain the values of limiting molar Conductance (Λ0), ionic association constant (KA), and the association diameter (R). The values of KA and R obtained for these three salts, namely, tetrabutylammonium bromide, sodium bromide, and sodium tetraphenylborate, suggests a weak electrostatic ion–solvent interaction and that they exist as free ions in all the solvent compositions and the temperature range covered in this study. The Walden products of these salts deviate from ideal behavior with varying temperature and solvent composition.

  • Conductance studies of tetrabutylammonium bromide sodium bromide and sodium tetraphenylborate in 2 butoxyethanol 1 water 2 mixtures at 298 15 303 15 308 15 and 313 15 k
    Journal of Chemical & Engineering Data, 2012
    Co-Authors: Binod Sharma, Ramesh C. Sharma
    Abstract:

    Electrical Conductances of solutions of tetrabutylammonium bromide (Bu4NBr), sodium bromide (NaBr), and sodium tetraphenylborate (NaBPh4) in 2-butoxyethanol (1) + water (2) mixture with 0.017, 0.037, 0.061, 0.092, and 0.132 mole fraction of 2-butoxyethanol have been reported at (298.15, 303.15, 308.15, and 313.15) K. The experimental values of electrical Conductances are analyzed using the 1978 Fuoss Conductance–concentration equation to obtain the values of limiting molar Conductance (Λ0), ionic association constant (KA), and the association diameter (R). The values of KA and R obtained for these three salts, namely, tetrabutylammonium bromide, sodium bromide, and sodium tetraphenylborate, suggests a weak electrostatic ion–solvent interaction and that they exist as free ions in all the solvent compositions and the temperature range covered in this study. The Walden products of these salts deviate from ideal behavior with varying temperature and solvent composition.

Moreno Vertovec – One of the best experts on this subject based on the ideXlab platform.

  • influence of the ectomycorrhizas formed by tuber melanosporum vitt on hydraulic Conductance and water relations of quercus ilex l seedlings
    Annals of Forest Science, 2000
    Co-Authors: Andrea Nardini, Sebastiano Salleo, Melvin T Tyree, Moreno Vertovec
    Abstract:

    The physiological impact of ectomycorrhizal infection was investigated in the association between Tuber melanosporum Vitt. and Quercus ilex L. A number of physiological parameters were investigated on 2-year-old seedlings inoculated for 22 months (I-seedlings) compared to non-inoculated plants (NI-seedlings). I-seedlings had a 100% infection rate in root tips compared to a 25% infection rate in root tips of NI-seedlings. I-seedlings had higher values of net assimilation and stomatal Conductance than NI – seedlings. Root hydraulic Conductance per unit root surface area of I-seedlings was much reduced to 0.44 〈 that of NI-seedlings but had 2.5〈 more fine root surface area than NI-seedlings. When root Conductance was scaled by leaf area, the I-seedlings had 1.27 〈 the root Conductance per unit leaf area compared to NI-seedlings. I-seedlings also had significantly higher hydraulic Conductances of shoots with leaves, of shoots without leaves and lower leaf blade hydraulic resistances. hydraulic Conductance / water relations / ectomycorrhiza / Quercus ilex L. / HPFM

  • Influence of the ectomycorrhizas formed by Tuber melanosporum Vitt. on hydraulic Conductance and water relations of Quercus ilex L. seedlings
    Annals of Forest Science, 2000
    Co-Authors: Andrea Nardinia, Melvin T Tyree, Sebastiano Salleo, Moreno Vertovec
    Abstract:

    The physiological impact of ectomycorrhizal infection was investigated in the association between Tuber melanosporum Vitt. and Quercus ilex L. A number of physiological parameters were investigated on 2-year-old seedlings inoculated for 22 months (I-seedlings) compared to non-inoculated plants (NI-seedlings). I-seedlings had a 100% infection rate in root tips compared to a 25% infection rate in root tips of NI-seedlings. I-seedlings had higher values of net assimilation and stomatal Conductance than NI-seedlings. Root hydraulic Conductance per unit root surface area of I-seedlings was much reduced to 0.44$\times$ that of NI-seedlings but had 2.5$\times$ more fine root surface area than NI-seedlings. When root Conductance was scaled by leaf area, the I-seedlings had 1.27$\times$ the root Conductance per unit leaf area compared to NI-seedlings. I-seedlings also had significantly higher hydraulic Conductances of shoots with leaves, of shoots without leaves and lower leaf blade hydraulic resistances.

Martin Pospischil – One of the best experts on this subject based on the ideXlab platform.

  • inhibition determines membrane potential dynamics and controls action potential generation in awake and sleeping cat cortex
    The Journal of Neuroscience, 2007
    Co-Authors: Michelle Rudolph, Martin Pospischil, Igor Timofeev, Alain Destexhe
    Abstract:

    Intracellular recordings of cortical neurons in awake cat and monkey show a depolarized state, sustained firing, and intense subthreshold synaptic activity. It is not known what Conductance dynamics underlie such activity and how neurons process information in such highly stochastic states. Here, we combine intracellular recordings in awake and naturally sleeping cats with computational models to investigate subthreshold dynamics of Conductances and how Conductance dynamics determine spiking activity. We show that during both wakefulness and the “up-states” of natural slow-wave sleep, membrane-potential activity stems from a diversity of combinations of excitatory and inhibitory synaptic Conductances, with dominant inhibition in most of the cases. Inhibition also provides the largest contribution to membrane potential fluctuations. Computational models predict that in such inhibition-dominant states, spikes are preferentially evoked by a drop of inhibitory Conductance, and that its signature is a transient drop of membrane Conductance before the spike. This pattern of Conductance change is indeed observed in estimates of spike-triggered averages of synaptic Conductances during wakefulness and slow-wave sleep up states. These results show that activated states are defined by diverse combinations of excitatory and inhibitory Conductances with pronounced inhibition, and that the dynamics of inhibition is particularly effective on spiking, suggesting an important role for inhibitory processes in both conscious and unconscious cortical states.

  • calculating event triggered average synaptic Conductances from the membrane potential
    Journal of Neurophysiology, 2007
    Co-Authors: Martin Pospischil, Zuzanna Piwkowska, Michelle Rudolph, Thierry Bal, Alain Destexhe
    Abstract:

    The optimal patterns of synaptic Conductances for spike generation in central neurons is a subject of considerable interest. Ideally such Conductance time courses should be extracted from membrane …

  • Inhibitory Conductance dynamics in cortical neurons during activated states.
    Neurocomputing, 2007
    Co-Authors: Martin Pospischil, Zuzanna Piwkowska, Michael Rudolph, Thierry Bal, Alain Destexhe
    Abstract:

    During activated states in vivo, neocortical neurons are subject to intense synaptic activity and high-amplitude membrane potential (V-m) fluctuations. These “high-Conductance” states may strongly affect the integrative properties of cortical neurons. We investigated the responsiveness of cortical neurons during different states using a combination of computational models and in vitro experiments (dynamic-clamp) in the visual cortex of adult guinea pigs. Spike responses were monitored following stochastic Conductance injection in both experiments and models. We found that cortical neurons can operate in a continuum between two different modes: during states with equal excitatory and inhibitory Conductances, the firing is mostly correlated with an increase in excitatory Conductance, which is a rather classic scenario. In contrast, during states dominated by inhibition, the firing is mostly related to a decrease in inhibitory Conductances (dis-inhibition). This model prediction was tested experimentally using dynamic-clamp, and the same modes of firing were identified. We also found that the signature of spikes evoked by dis-inhibition is a transient drop of the total membrane Conductance prior to the spike, which is typical of states with dominant inhibitory Conductances. Such a drop should be identifiable from intracellular recordings in vivo, which would provide an important test for the presence of inhibition-dominated states. In conclusion, we show that in artificial activated states, not only inhibition can determine the Conductance state of the membrane, but inhibitory inputs may also have a determinant influence on spiking. Future analyses and models should focus on verifying if such a determinant influence of inhibitory Conductance dynamics is also present in vivo.