Dynamical Casimir effect for a massless scalar field between two concentric spherical shells

In this work we consider the dynamical Casimir effect for a massless scalar field -- under Dirichlet boundary conditions -- between two concentric spherical shells. We obtain a general expression for the average number of particle creation, for an arbitrary law of radial motion of the spherical shells, using two distinct methods: by computing the density operator of the system and by calculating the Bogoliubov coefficients. We apply our general expression to breathing modes: when only one of the shells oscillates and when both shells oscillate in or out of phase. We also analyze the number of particle production and compare it with the results for the case of plane geometry.Comment: Final version. To apear in Physical Review

Toward a multiscale modeling framework for understanding serotonergic function

Despite its importance in regulating emotion and mental wellbeing, the complex structure and function of the serotonergic system present formidable challenges toward understanding its mechanisms. In this paper, we review studies investigating the interactions between serotonergic and related brain systems and their behavior at multiple scales, with a focus on biologically-based computational modeling. We first discuss serotonergic intracellular signaling and neuronal excitability, followed by neuronal circuit and systems levels. At each level of organization, we will discuss the experimental work accompanied by related computational modeling work. We then suggest that a multiscale modeling approach that integrates the various levels of neurobiological organization could potentially transform the way we understand the complex functions associated with serotonin

Conditional corticotropin-releasing hormone overexpression in the mouse forebrain enhances rapid eye movement sleep

Impaired sleep and enhanced stress hormone secretion are the hallmarks of stress-related disorders, including major depression. The central neuropeptide, corticotropin-releasing hormone (CRH), is a key hormone that regulates humoral and behavioral adaptation to stress. Its prolonged hypersecretion is believed to play a key role in the development and course of depressive symptoms, and is associated with sleep impairment. To investigate the specific effects of central CRH overexpression on sleep, we used conditional mouse mutants that overexpress CRH in the entire central nervous system (CRH-COE-Nes) or only in the forebrain, including limbic structures (CRH-COE-Cam). Compared with wild-type or control mice during baseline, both homozygous CRH-COE-Nes and -Cam mice showed constantly increased rapid eye movement (REM) sleep, whereas slightly suppressed non-REM sleep was detected only in CRH-COE-Nes mice during the light period. In response to 6-h sleep deprivation, elevated levels of REM sleep also became evident in heterozygous CRH-COE-Nes and -Cam mice during recovery, which was reversed by treatment with a CRH receptor type 1 (CRHR1) antagonist in heterozygous and homozygous CRH-COE-Nes mice. The peripheral stress hormone levels were not elevated at baseline, and even after sleep deprivation they were indistinguishable across genotypes. As the stress axis was not altered, sleep changes, in particular enhanced REM sleep, occurring in these models are most likely induced by the forebrain CRH through the activation of CRHR1. CRH hypersecretion in the forebrain seems to drive REM sleep, supporting the notion that enhanced REM sleep may serve as biomarker for clinical conditions associated with enhanced CRH secretion

Reconstruction of the field excitatory post-synaptic potentials in the dentate gyrus from amperometric biosensor signal

Introduction: Local field potentials (LFP) information can be obtained from amperometric neurochemical recordings. However, conversion from the amperometric high frequency components (HFC) to conventional LFP is a challenging task since the electrode impedance is difficult to determine and the electrical properties of microelectrodes change with the frequency. Objective: To find and test a feasible and reproducible method to reconstruct field excitatory post-synaptic potentials (fEPSPs) in the dentate gyrus of the hippocampal formation from amperometric HFC. Materials and methods: The electrode properties were modelled as an equivalent circuit consisting of 3 resistances and 2 capacitances. A single voltage pulse allowed estimation of the resistances and capacitances values. After determination of the electrode impedance, FFT and Inverse FFT were used to convert the amperometric signal to LFPs. Platinum electrodes and biosensors responses for different voltage pulses at different holding potentials were tested in saline or in PBS. Reconstructions of the evoked potentials elicited in the dentate gyrus of rats (n=3) and mice (n=2) by stimulation of the perforant pathway were compared to electrophysiological recordings obtained subsequently in the same preparations. Long term potentiation (LTP) was induced in rats by high frequency stimulation of the perforant pathway and demonstrated by the reconstructed fEPSPs. Results: The estimated values of the resistances and capacitances of the equivalent circuit for different platinum electrodes and biosensors were found to be quite independent on the amplitude of the voltages steps (0.5-2 mV) and DC values (0-500 mV). Our method allowed perfect overlapping between reconstructed fEPSPs and true voltage recordings. Reconstructed fEPSPs showed typical inversion of the responses on the depth profile. Analysis of the slope of the rising phase of the fEPSPs showed potentiation of the synaptic efficacy in rats after high frequency stimulation. Conclusions: Our results showed that for specific electrophysiological purposes a relatively simple electrode model can work satisfactorily , allowing the reconstruction of the fEPSPs in the dentate gyrus in order to demonstrate LTP during acquisition of neurochemical recordings