1,026 research outputs found
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
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
The Cortical States of Wakefulness
Cortical neurons process information on a background of spontaneous, ongoing activity with distinct spatiotemporal profiles defining different cortical states. During wakefulness, cortical states alter constantly in relation to behavioral context, attentional level or general motor activity. In this review article, we will discuss our current understanding of cortical states in awake rodents, how they are controlled, their impact on sensory processing, and highlight areas for future research. A common observation in awake rodents is the rapid change in spontaneous cortical activity from high-amplitude, low-frequency (LF) fluctuations, when animals are quiet, to faster and smaller fluctuations when animals are active. This transition is typically thought of as a change in global brain state but recent work has shown variation in cortical states across regions, indicating the presence of a fine spatial scale control system. In sensory areas, the cortical state change is mediated by at least two convergent inputs, one from the thalamus and the other from cholinergic inputs in the basal forebrain. Cortical states have a major impact on the balance of activity between specific subtypes of neurons, on the synchronization between nearby neurons, as well as the functional coupling between distant cortical areas. This reorganization of the activity of cortical networks strongly affects sensory processing. Thus cortical states provide a dynamic control system for the moment-by-moment regulation of cortical processing
TREATMENT OF SHIZOPHRENIC PATIENTS AND rTMS
Introduction: Schizophrenia (SCH) is a heterogeneous syndrome characterized by positive and negative symptoms. Despite
appropriate medication, about 1/4 of patients suffer for refractory positive and/or negative symptoms, which are associated with
functional handicap, increase of duration and of the number of hospitalizations. Numerous studies have suggested that the
pathophysiology of auditory hallucinations (AH) is related to a hyper activity of the left temporoparietal cortex (TPC). On the other
hand, negative symptoms are associated with a prefrontal hypoactivity and the efficiency of pharmacological treatments is frequently
partial. Repetitive transcranial magnetic stimulation (rTMS) is a non-invasive brain stimulation tool with excellent tolerability and
safety. Given its hypothesized mechanisms of action and the clinical beneficial effects obtained in several types of pathology (Aleman
et al. 2007), the efficacy of rTMS has been investigated for drug-resistant SCH symptoms.
Objective: Our objective is to expose the knowledge concerning the rTMS use in the treatment of these symptoms and to purpose
a critical analysis of these data.
Method: a systematic review of the literature has been conducted using NIH Pubmed. The following search terms were used:
TMS - rTMS - Schizophrenia - negative symptoms - hallucinations.
Results: Concerning the treatment of AH, 16 publications and 4 meta analyses were selected. For the negative symptoms, we
retained 16 studies and 3 meta analyses. The most extensively investigated application for rTMS in SCH is the use of low-frequency
stimulation to the left TPC with the aim to improve AH symptomatology. When compared to sham, this type of acute course of rTMS
has been proven to induce a substantial and significant reduction in AH. But this effect does not seem long-lasting and maintenance
protocols must be developed. Concerning negative symptoms, the results are less solid but we find some works which demonstrate an
improvement of these symptoms while various stimulation parameters were used. Recently, new parameters of stimulation in
particular the theta burst stimulation have permitted us to obtain larger effects with longer duration. The interest of these new
parameters will be discussed here.
Conclusion: Overall, rTMS studies have demonstrated some promise in the treatment of SCH. However, more research is
required to enhance rTMS efficacy and increase its beneficial effect duration and to test new therapeutic strategies in this topic
Multiple Two-Photon Targeted Whole-Cell Patch-Clamp Recordings From Monosynaptically Connected Neurons in vivo
Although we know a great deal about monosynaptic connectivity, transmission and integration in the mammalian nervous system from in vitro studies, very little is known in vivo. This is partly because it is technically difficult to evoke action potentials and simultaneously record small amplitude subthreshold responses in closely (<150 ÎŒm) located pairs of neurons. To address this, we have developed in vivo two-photon targeted multiple (2â4) whole-cell patch clamp recordings of nearby neurons in superficial cortical layers 1â3. Here, we describe a step-by-step guide to this approach in the anesthetized mouse primary somatosensory cortex, including: the design of the setup, surgery, preparation of pipettes, targeting and acquisition of multiple whole-cell recordings, as well as in vivo and post hoc histology. The procedure takes ~4 h from start of surgery to end of recording and allows examinations both into the electrophysiological features of unitary excitatory and inhibitory monosynaptic inputs during different brain states as well as the synaptic mechanisms of correlated neuronal activity
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
Scattering compensation by focus scanning holographic aberration probing (F-SHARP)
A long-standing goal in biomedical imaging, the control of light inside turbid media, requires knowledge of how the phase and amplitude of an illuminating wavefront are transformed as the electric field propagates inside a scattering sample onto a target plane. So far, it has proved challenging to non-invasively characterize the scattered optical wavefront inside a disordered medium. Here, we present a non-invasive scattering compensation method, termed F-SHARP, which allows us to measure the scattered electric-field point spread function (E-field PSF) in three dimensions. Knowledge of the phase and amplitude of the E-field PSF makes it possible to optically cancel sample turbulence. We demonstrate the imaging capabilities of this technique on a variety of samples and notably through vertebrate brains and across thinned skull in vivo
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