1,300 research outputs found
Corollary discharge inhibition and audition in the stridulating cricket
The romantic notion of crickets singing on a warm summer's evening is quickly dispelled when one comes ear to ear with a stridulating male. Remarkably, stridulating male crickets are able to hear sounds from the environment despite generating a 100db song (Heiligenberg 1969; Jones and Dambach 1973). This review summarises recent work examining how they achieve this feat of sensory processing. While the responsiveness of the crickets' peripheral auditory system (tympanic membrane, tympanic nerve, state of the acoustic spiracle) is maintained during sound production, central auditory neurons are inhibited by a feedforward corollary discharge signal precisely timed to coincide with the auditory neurons' maximum response to self-generated sound. In this way, the corollary discharge inhibition prevents desensitisation of the crickets' auditory pathway during sound productio
Single synaptic inputs drive high-precision action potentials in parvalbumin expressing GABA-ergic cortical neurons in vivo
A defining feature of cortical layer 2/3 excitatory neurons is their sparse activity, often firing in singlets of action potentials. Local inhibitory neurons are thought to play a major role in regulating sparseness, but which cell types are recruited by single excitatory synaptic inputs is unknown. Using multiple, targeted, in vivo whole-cell recordings, we show that single EPSPs have little effect on the firing rates of excitatory neurons and somatostatin-expressing GABA-ergic inhibitory neurons but evoke precisely timed action potentials in parvalbumin-expressing inhibitory neurons. Despite a EPSP decay time of 7.8âms, the evoked action potentials were almost completely restricted to the EPSP rising phase (~0.5âms). Evoked parvalbumin-expressing neuron action potentials go on to inhibit the local excitatory network, thus providing a pathway for single spike evoked disynaptic inhibition which may enforce sparse and precisely timed cortical signaling
Matching cell type to function in cortical circuits
In this issue of Neuron, Pinto and Dan (2015) performed single-cell calcium imaging in the mouse dorsomedial prefrontal cortex to reveal correlated, cell-type-specific responses in three major GABA-ergic interneuron subtypes during a goal-directed sensory discrimination task
Theory of rigid-plane phonon modes in layered crystals
The lattice dynamics of low-frequency rigid-plane modes in metallic (graphene
multilayers, GML) and in insulating (hexagonal boron-nitride multilayers, BNML)
layered crystals is investigated. The frequencies of shearing and compression
(stretching) modes depend on the layer number {\EuScript N} and are presented
in the form of fan diagrams. The results for GML and BNML are very similar. In
both cases only the interactions (van der Waals and Coulomb) between
nearest-neighbor planes are effective, while the interactions between more
distant planes are screened. A comparison with recent Raman scattering results
on low-frequency shear modes in GML [Tan {\it et al.}, arXiv:1106.1146v1
(2011)] is made. Relations with the low-lying rigid-plane phonon dispersions in
the bulk materials are established. Master curves which connect the fan diagram
frequencies for any given {\EuScript N} are derived. Static and dynamic
thermal correlation functions for rigid-layer shear and compression modes are
calculated. The results might be of use for the interpretation of friction
force experiments on multilayer crystals
Spectral and stratigraphic mapping of hydrated sulfate and phyllosilicate-bearing deposits in northern Sinus Meridiani, Mars
We present detailed stratigraphic and spectral analyses that focus on a region in
northern Sinus Meridiani located between 1°N to 5°N latitude and 3°W to 1°E longitude.
Several stratigraphically distinct units are defined and mapped using morphologic
expression, spectral properties, and superposition relationships. Previously unreported
exposures of hydrated sulfates and Fe/Mg smectites are identified using MRO CRISM and
MEX OMEGA nearâinfrared (1.0 to 2.5 ”m) spectral reflectance observations. Layered
deposits with monohydrated and polyhydrated sulfate spectral signatures that occur in
association with a northeastâsouthwest trending valley are reexamined using highresolution
CRISM, HiRISE, and CTX images. Layers that are spectrally dominated by
monohydrated and polyhydrated sulfates are intercalated. The observed compositional
layering implies that multiple wetting events, brine recharge, or fluctuations in evaporation
rate occurred. We infer that these hydrated sulfateâbearing layers were unconformably
deposited following the extensive erosion of preexisting layered sedimentary rocks and
may postdate the formation of the sulfateâ and hematiteâbearing unit analyzed by the MER
Opportunity rover. Therefore, at least two episodes of deposition separated by an
unconformity occurred. Fe/Mg phyllosilicates are detected in units that predate the sulfateand
hematiteâbearing unit. The presence of Fe/Mg smectite in older units indicates that the
relatively low pH formation conditions inferred for the younger sulfateâ and hematitebearing
unit are not representative of the aqueous geochemical environment that prevailed
during the formation and alteration of earlier materials. Sedimentary deposits indicative of
a complex aqueous history that evolved over time are preserved in Sinus Meridiani, Mars
How Much Do Benzodiazepines Matter for Electroconvulsive Therapy in Patients With Major Depression?
BACKGROUND: Electroconvulsive therapy (ECT) is one of the most effective treatments for major depressive disorder (MDD), especially in cases of treatment-resistant MDD. Because of their pharmacological profiles, benzodiazepines (BZDs) are suspected to decrease the efficacy of ECT. This study investigated the effect of BZDs on ECT-induced clinical outcomes and ECT course parameters in patients with MDD.
METHOD: The impact of BZDs on severity of depression (Montgomery-Asberg Depression Rating Scale scores) and on ECT course parameters (seizure threshold, clinical and electroencephalographic seizure duration) was investigated in 70 patients with MDD who received an ECT course using dose-titration method (22 received concomitant BZDs).
RESULTS: Lower remission rates (52.0%) and smaller decreases in Montgomery-Asberg Depression Rating Scale scores were observed in the non-BZD group than in the BZD group (81.2%, P = 0.02). There were no significant differences between the 2 groups regarding seizure duration and seizure threshold.
LIMITATIONS: This was a retrospective study. Impact of BZDs on anxiety and cognition was not assessed.
CONCLUSIONS: Benzodiazepines increased the clinical efficacy of ECT when delivered using dose-titration method and bitemporal stimulation. Further studied are needed to understand the interaction between BZDs and ECT on clinical outcomes
Modal mineralogy of planetary surfaces from visible and near-infrared spectral data
Real planetary surfaces are composed of several to many different minerals and ices. Deconvolving a reflectance spectrum to material abundance in an unambiguous way is difficult, because the spectra are complex nonlinear functions of grain size, abundance, and material opacity. Multiple scattering models can provide approximate solutions to the radiative transfer in a particulate medium. The paper examines the different approaches which deal with the theory of radiative transfer on atmosphereless bodies. We present the relative merits of two scattering theories based on the equivalent slab model: the extensively used Hapke theory [1] and the Shkuratov theory [2]. The performances of the two models for determining mineral abundance in multicomponent mixtures are also evaluated using laboratory data. Finally, one application on real planetary surfaces will be shown
Recovery of surface reflectance spectra and evaluation of the optical depth of aerosols in the near-IR using a Monte-Carlo approach: Application to the OMEGA observations of high latitude regions of Mars
We present a model of radiative transfer through atmospheric particles based
on Monte Carlo methods. This model can be used to analyze and remove the
contribution of aerosols in remote sensing observations. We have developed a
method to quantify the contribution of atmospheric dust in near-IR spectra of
the Martian surface obtained by the OMEGA imaging spectrometer on board Mars
Express. Using observations in the nadir pointing mode with significant
differences in solar incidence angles, we can infer the optical depth of
atmospheric dust, and we can retrieve the surface reflectance spectra free of
aerosol contribution. Martian airborne dust properties are discussed and
constrained from previous studies and OMEGA data. We have tested our method on
a region at 90{\deg}E and 77{\deg}N extensively covered by OMEGA, where
significant variations of the albedo of ice patches in the visible have been
reported. The consistency between reflectance spectra of ice-covered and
ice-free regions recovered at different incidence angles validates our
approach. The optical depth of aerosols varies by a factor 3 in this region
during the summer of Martian year 27. The observed brightening of ice patches
does not result from frost deposition but from a decrease in the dust
contamination of surface ice and (to a lower extent) from a decrease in the
optical thickness of atmospheric dust. Our Monte Carlo-based model can be
applied to recover the spectral reflectance characteristics of the surface from
OMEGA spectral imaging data when the optical thickness of aerosols can be
evaluated. It could prove useful for processing image cubes from the Compact
Reconnaissance Imaging Spectrometer for Mars (CRISM) on board the Mars
Reconnaissance Orbiter (MRO)
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