Short-term depression shapes information transmission in a constitutively active GABAergic synapse

AbstractShort-term depression is a low-pass filter of synaptic information, reducing synaptic information transfer at high presynaptic firing frequencies. Consequently, during elevated presynaptic firing, little information passes to the postsynaptic neuron. However, many neurons fire at relatively high frequencies all the time. Does depression silence their synapses? We tested this apparent contradiction in the indirect pathway of the basal ganglia. Using numerical modeling and whole-cell recordings from single entopeduncular nucleus (EP) neurons in rat brain slices, we investigated how different firing rates of globus pallidus (GP) neurons affect information transmission to the EP. Whole-cell recordings showed significant variability in steady-state depression, which decreased as stimulation frequency increased. Modeling predicted that this variability would translate into different postsynaptic noise levels during constitutive presynaptic activity. Our simulations further predicted that individual GP-EP synapses mediate gain control. However, when we consider the integration of multiple inputs, the broad range of GP firing rates would enable different modes of information transmission. Finally, we predict that changes in dopamine levels can shift the action of GP neurons from rate coding to gain modulation. Our results thus demonstrate how short-term depression shapes information transmission in the basal ganglia in particular and via GABAergic synapses in general.

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Short term depression shapes information transmission in a constitutively active GABAergic synapse

10.1101/370833 ◽

2018 ◽

Author(s):

Hagar Lavian ◽

Alon Korngreen

Keyword(s):

Basal Ganglia ◽

Information Transmission ◽

Globus Pallidus ◽

Synaptic Depression ◽

Indirect Pathway ◽

Short Term ◽

Gabaergic Synapse ◽

Firing Rates ◽

Low Pass ◽

Constitutively Active

AbstractShort-term depression is a low pass filter of synaptic information that reduces and flattens synaptic information transfer at high presynaptic firing frequencies. This view questions the relevance of spontaneous high firing rates in some networks. In the indirect pathway of the basal ganglia, spontaneously active neurons in the globus pallidus (GP) form depressing inhibitory synapses in the basal ganglia output nuclei. Using numerical modeling and whole-cell recordings from single entopeduncular nucleus (EP) neurons in rat brain slices we investigated the contribution of the different firing rates of GP neurons to information transmission in the indirect pathway. Wholecell recordings showed significant variability in steady-state depression which decreased as stimulation frequency increased. Modeling predicted that this variability would translate into different postsynaptic noise levels during constitutive presynaptic activity. Our simulations further predicted that individual GP-EP synapses mediate gain control. However, when we consider integration of multiple inputs, the large range of GP firing rates would enable different modes of information transmission in which the magnitude and temporal features of postsynaptic modulation would change as a function of present and past firing rates of GP neurons. Finally, we predict that changes in dopamine levels can shift the action of GP neurons from rate coding to gain modulation. Our results thus demonstrate how short-term synaptic depression shapes information transmission in the basal ganglia in particular and via GABAergic synapses in general.Significant statementSynapses displaying short-term depression are low-pass filters of synaptic input. Consequently, when presynaptic firing is high, little information passes to the postsynaptic neuron. However, many neurons fire at relatively high frequencies all the time. Are their synapses constantly silenced by depression? We tested this apparent contradiction in the indirect pathway of the basal ganglia, where neurons from the globus pallidus (GP) form constitutively active depressing synapses on basal ganglia output. We hypothesized that the different rates of ongoing activity underlie different modes of action for GP neurons. We show that the synaptic and structural properties of the indirect pathway map GP baseline frequencies to different postsynaptic signals, thus demonstrating how short-term synaptic depression shapes information transmission in the basal ganglia.

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Role of slow temporal dynamics in reliable activity of stochastically driven neurons

10.1101/2020.12.11.422204 ◽

2020 ◽

Author(s):

Subhadra Mokashe ◽

Suhita Nadkarni

Keyword(s):

Temporal Dynamics ◽

Network Motif ◽

Neuronal Firing ◽

Input Current ◽

Switching Frequency ◽

Quiescent State ◽

Extrinsic Noise ◽

Gabaergic Synapse ◽

Pass Filter ◽

Low Pass Filter

ABSTRACTNeuronal networks maintain robust patterns of activity despite a backdrop of noise from various sources. Mutually inhibiting neurons is a standard network motif implicated in rhythm generation. In an elementary network motif of two neurons capable of swapping from an active state to a quiescent state, we ask how different sources of stochasticity alter firing patterns. In this system, the alternating activity occurs via combined action of a calcium-dependent potassium current, sAHP (slow afterhyperpolarization), and a fast GABAergic synapse. We show that simulating extrinsic noise arising from background activity extends the dynamical range of neuronal firing. Extrinsic noise also has the effect of increasing the switching frequency via a faster build-up of sAHP current. We show that switching frequency as a function of input current has a non-monotonic behavior. Interestingly the noise tolerance of this system varies with the input current. It shows maximum robustness to noise at an input current that corresponds to the minimum switching frequency between the neurons. The slow decay time scale of sAHP conductance allows neurons to act as a low-pass filter, attenuate noise, and integrate over ion channel fluctuations. Additionally, we show that the slow inactivation time of the sAHP channel allows the neuron to act as an action potential counter. We propose that this intrinsic property of the current allows the network to maintain rhythmic activity critical for various functions, despite the noise, and operate as a temporal integrator.

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Research on the Short-Time Bias Stability of the Solid Vibration Beam Gyroscope

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.179-180.86 ◽

2011 ◽

Vol 179-180 ◽

pp. 86-91

Author(s):

Xian Lin Bai ◽

Yong Le Lu ◽

Yu Liu

Keyword(s):

Solid State ◽

Output Signal ◽

Transient Solution ◽

Short Term ◽

Pass Filter ◽

Low Pass Filter ◽

Bias Stability ◽

Low Pass ◽

Simulation And Experiment ◽

Short Time

In this paper, Short-term bias stability of solid state vibration beam gyroscope is studied. Based on the dynamical equation of solid vibration beam gyroscope, the elements effecting the zero stability which effects the short term bias stability was discussed. The computed result shows that the main factors for short-term bias stability is transient solution error. The output signal has been filtered by the low pass filter, according to the characteristic of transient solution error. Simulation results demonstrate that low-pass filter can effectively suppress the error of output signal. In addition, the signal of solid state vibrating gyroscope filtered by low-pass filter agrees well with the simulation result. From the simulation and experiment data, the validity of the model and the feasibility of the filtering programs has been proved.

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Toward unifying short-term and next-day convection-allowing ensemble forecast systems with a continuously-cycling 3-km ensemble Kalman filter over the entire conterminous United States

Weather and Forecasting ◽

10.1175/waf-d-20-0110.1 ◽

2020 ◽

pp. 1-83

Author(s):

Craig S. Schwartz ◽

Glen S. Romine ◽

David C. Dowell

Keyword(s):

United States ◽

Kalman Filter ◽

High Resolution ◽

Ensemble Kalman Filter ◽

Ensemble Forecast ◽

Grid Spacing ◽

Short Term ◽

Pass Filter ◽

Low Pass Filter ◽

Horizontal Grid

Abstract Using the Weather Research and Forecasting model, 80-member ensemble Kalman filter (EnKF) analyses with 3-km horizontal grid spacing were produced over the entire conterminous United States (CONUS) for 4 weeks using 1-h continuous cycling. For comparison, similarly configured EnKF analyses with 15-km horizontal grid spacing were also produced. At 0000 UTC, 15- and 3-km EnKF analyses initialized 36-h, 3-km, 10-member ensemble forecasts that were verified with a focus on precipitation. Additionally, forecasts were initialized from operational Global Ensemble Forecast System (GEFS) initial conditions (ICs) and experimental “blended” ICs produced by combining large scales from GEFS ICs with small scales from EnKF analyses using a low-pass filter. The EnKFs had stable climates with generally small biases, and precipitation forecasts initialized from 3-km EnKF analyses were more skillful and reliable than those initialized from downscaled GEFS and 15-km EnKF ICs through 12–18 and 6–12 h, respectively. Conversely, after 18 h, GEFS-initialized precipitation forecasts were better than EnKF-initialized precipitation forecasts. Blended 3-km ICs reflected the respective strengths of both GEFS and high-resolution EnKF ICs and yielded the best performance considering all times: blended 3-km ICs led to short-term forecasts with similar or better skill and reliability than those initialized from unblended 3-km EnKF analyses and ~18–36-h forecasts possessing comparable quality as GEFS-initialized forecasts. This work likely represents the first time a convection-allowing EnKF has been continuously cycled over a region as large as the entire CONUS, and results suggest blending high-resolution EnKF analyses with low-resolution global fields can potentially unify short-term and next-day convection-allowing ensemble forecast systems under a common framework.

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