Serotonin drives a novel GABAergic synaptic current recorded in rat cerebellar purkinje cells: a lugaro cell to Purkinje cell synapse

We recorded a novel fast GABAergic synaptic current in cerebellar Purkinje cells in rat brain slices using patch-clamp techniques. Because of a relatively low sensitivity to bicuculline, these currents can be recorded under conditions in which basket and stellate cell inputs are blocked. The observations that the novel synaptic currents occur spontaneously only in the presence of serotonin, and the specific limited positions in the slice from which they can be electrically evoked, suggest that the presynaptic cell is the Lugaro cell. Cell-attached recordings confirm that the Lugaro cell is the only interneuron in the cerebellar cortex with firing behavior consistent with the spontaneous activity recorded in Purkinje cells. The input shows a strong presynaptic modulation mediated by GABAA receptors, resulting in a dynamic range from almost 0 to >90% release probability. Modeling GABAA receptor responses to different GABA transients suggests that the relatively low sensitivity of the synaptic currents to bicuculline, compared with the higher affinity GABAA receptor antagonist SR-95531 (2-(3-carboxypropyl)-3-amino-6-(4-methoxyphenyl) pyridazinium), is attributable to an unusually long GABA dwell time and/or high GABA concentration in the synaptic cleft. The significance of this novel input is discussed in relation to other GABAergic synapses impinging on Purkinje cells. We suggest that the release of GABA onto Purkinje cells from Lugaro cells would primarily occur during motor activity under conditions in which the activity of basket and stellate cells might be inhibited

Serotonin drives a novel GABAergic synaptic current recorded in rat cerebellar purkinje cells: a lugaro cell to purkinje cell synapse

We recorded a novel fast GABAergic synaptic current in cerebellar Purkinje cells in rat brain slices using patch-clamp techniques. Because of a relatively low sensitivity to bicuculline, these currents can be recorded under conditions in which basket and stellate cell inputs are blocked. The observations that the novel synaptic currents occur spontaneously only in the presence of serotonin, and the specific limited positions in the slice from which they can be electrically evoked, suggest that the presynaptic cell is the Lugaro cell. Cell-attached recordings confirm that the Lugaro cell is the only interneuron in the cerebellar cortex with firing behavior consistent with the spontaneous activity recorded in Purkinje cells. The input shows a strong presynaptic modulation mediated by GABAA receptors, resulting in a dynamic range from almost 0 to >90% release probability. Modeling GABAA receptor responses to different GABA transients suggests that the relatively low sensitivity of the synaptic currents to bicuculline, compared with the higher affinity GABAA receptor antagonist SR-95531 (2-(3-carboxypropyl)-3-amino-6-(4-methoxyphenyl) pyridazinium), is attributable to an unusually long GABA dwell time and/or high GABA concentration in the synaptic cleft. The significance of this novel input is discussed in relation to other GABAergic synapses impinging on Purkinje cells. We suggest that the release of GABA onto Purkinje cells from Lugaro cells would primarily occur during motor activity under conditions in which the activity of basket and stellate cells might be inhibited

Effective diffusion constant in a two dimensional medium of charged point scatterers

We obtain exact results for the effective diffusion constant of a two dimensional Langevin tracer particle in the force field generated by charged point scatterers with quenched positions. We show that if the point scatterers have a screened Coulomb (Yukawa) potential and are uniformly and independently distributed then the effective diffusion constant obeys the Volgel-Fulcher-Tammann law where it vanishes. Exact results are also obtained for pure Coulomb scatterers frozen in an equilibrium configuration of the same temperature as that of the tracer.Comment: 9 pages IOP LaTex, no figure

The Steady-State Growth Theorem: A Comment on Uzawa (1961)

This brief note revisits the proof of the Steady-State Growth Theorem, first provided by Uzawa (1961). We provide a clear statement of the theorem and a new version of Uzawa's proof that makes the intuition underlying the result more apparent.

Dynamical transition for a particle in a squared Gaussian potential

We study the problem of a Brownian particle diffusing in finite dimensions in a potential given by $\psi= \phi^2/2$ where $\phi$ is Gaussian random field. Exact results for the diffusion constant in the high temperature phase are given in one and two dimensions and it is shown to vanish in a power-law fashion at the dynamical transition temperature. Our results are confronted with numerical simulations where the Gaussian field is constructed, in a standard way, as a sum over random Fourier modes. We show that when the number of Fourier modes is finite the low temperature diffusion constant becomes non-zero and has an Arrhenius form. Thus we have a simple model with a fully understood finite size scaling theory for the dynamical transition. In addition we analyse the nature of the anomalous diffusion in the low temperature regime and show that the anomalous exponent agrees with that predicted by a trap model.Comment: 18 pages, 4 figures .eps, JPA styl

Renormalization of Drift and Diffusivity in Random Gradient Flows

We investigate the relationship between the effective diffusivity and effective drift of a particle moving in a random medium. The velocity of the particle combines a white noise diffusion process with a local drift term that depends linearly on the gradient of a gaussian random field with homogeneous statistics. The theoretical analysis is confirmed by numerical simulation. For the purely isotropic case the simulation, which measures the effective drift directly in a constant gradient background field, confirms the result previously obtained theoretically, that the effective diffusivity and effective drift are renormalized by the same factor from their local values. For this isotropic case we provide an intuitive explanation, based on a {\it spatial} average of local drift, for the renormalization of the effective drift parameter relative to its local value. We also investigate situations in which the isotropy is broken by the tensorial relationship of the local drift to the gradient of the random field. We find that the numerical simulation confirms a relatively simple renormalization group calculation for the effective diffusivity and drift tensors.Comment: Latex 16 pages, 5 figures ep

Crystallization and preliminary X-ray analysis of a D-alanyl-D-alanine ligase (EcDdlB) from Escherichia coli

A recombinant form of Escherichia coli DdlB (EcDdlB) has been prepared and cocrystallized with ADP and D-alanyl-D-alanine to represent the ternary complex of EcDdlB. Furthermore, EcDdlB has been cocrystallized under the same conditions with the ligands ATP and D-alanyl-D-alanine, representing the product-inhibited complex. The crystals belonged to space group P212121, with unit-cell parameters a = 53.0, b = 97.6, c = 109.5 Å and a = 51.2, b = 97.8, c = 110.1 Å, respectively, and both contained two molecules in the asymmetric unit. Complete data sets were collected to 1.5 and 1.4 Å resolution, respectively, from single crystals under cryogenic conditions using synchrotron radiation

Distributed Deep Learning for Question Answering

This paper is an empirical study of the distributed deep learning for question answering subtasks: answer selection and question classification. Comparison studies of SGD, MSGD, ADADELTA, ADAGRAD, ADAM/ADAMAX, RMSPROP, DOWNPOUR and EASGD/EAMSGD algorithms have been presented. Experimental results show that the distributed framework based on the message passing interface can accelerate the convergence speed at a sublinear scale. This paper demonstrates the importance of distributed training. For example, with 48 workers, a 24x speedup is achievable for the answer selection task and running time is decreased from 138.2 hours to 5.81 hours, which will increase the productivity significantly.Comment: This paper will appear in the Proceeding of The 25th ACM International Conference on Information and Knowledge Management (CIKM 2016), Indianapolis, US

Continuum Derrida Approach to Drift and Diffusivity in Random Media

By means of rather general arguments, based on an approach due to Derrida that makes use of samples of finite size, we analyse the effective diffusivity and drift tensors in certain types of random medium in which the motion of the particles is controlled by molecular diffusion and a local flow field with known statistical properties. The power of the Derrida method is that it uses the equilibrium probability distribution, that exists for each {\em finite} sample, to compute asymptotic behaviour at large times in the {\em infinite} medium. In certain cases, where this equilibrium situation is associated with a vanishing microcurrent, our results demonstrate the equality of the renormalization processes for the effective drift and diffusivity tensors. This establishes, for those cases, a Ward identity previously verified only to two-loop order in perturbation theory in certain models. The technique can be applied also to media in which the diffusivity exhibits spatial fluctuations. We derive a simple relationship between the effective diffusivity in this case and that for an associated gradient drift problem that provides an interesting constraint on previously conjectured results.Comment: 18 pages, Latex, DAMTP-96-8