Visual Discrimination, Serial Reversal, and Extinction Learning in the

Duchenne muscular dystrophy (DMD) is the most common form of muscular dystrophy and the most common neuromuscular disorder. In addition to neuromuscular consequences, some individuals with DMD experience global intellectual dysfunction and executive dysfunction of unknown mechanistic origin. The cognitive profile of the mdx mouse, the most commonly used mouse model of DMD, has been incompletely characterized and has never been assessed using the touchscreen operant conditioning paradigm. The touchscreen paradigm allows the use of protocols that are virtually identical to those used in human cognitive testing and may, therefore, provide the most translational paradigm for quantifying mouse cognitive function. In the present study, we used the touchscreen paradigm to assess the effects of the mdx mutation on visual discrimination learning, serial reversal learning, and extinction learning. To enable measuring task-dependent learning and memory processes while holding demands on sensory-driven information processing constant, we developed equally salient visual stimuli and used them on all experimental stages. Acquisition of the initial pairwise visual discrimination was facilitated in mdx mice relative to wildtype littermates; this effect was not explained by genotypic differences in impulsivity, motivation, or motor deficits. The mdx mutation had no effect on serial reversal or extinction learning. Together, findings from this study and previous studies suggest that mdx effects on cognitive function are task-specific and may be influenced by discrimination type (spatial, visual), reward type (food, escape from a non-preferred environment), sex, and genetic background

Stimulus Complexity and Mouse Strain Drive Escalation of Operant Sensation Seeking Within and Across Sessions in C57BL/6J and DBA/2J Mice.

Sensation seeking is a heritable trait that is genetically correlated with substance use; the shared genetic mechanisms underlying these traits are largely unknown. The relationship of sensation seeking and substance use has practical importance because discovering genes that drive sensation seeking can reveal genes driving substance use, and quantification of sensation seeking in mice is higher throughput and less technically challenging than quantification of volitional drug use. In order to fully understand the genetic mechanisms driving sensation seeking, it is critical to first understand the nongenetic factors driving sensation seeking. In the present study, we used the operant sensation seeking paradigm to assess the effects of stimulus complexity on sensation seeking in C57BL/6J and DBA/2J mice. These strains are the founders of the BXD recombinant inbred mouse panel which enables the discovery of genes driving phenotypic variation. This study led to four principal conclusions. First, all sensory stimuli used in the study, regardless of complexity or number of stimulus modalities, served as reinforcers for C57BL/6J and DBA/2J mice. Second, for both C57BL/6J and DBA/2J mice, sensation seeking for a high complexity sensory stimulus was significantly greater than sensation seeking for a low complexity sensory stimulus. Third, for both C57BL/6J and DBA/2J mice, sensation seeking escalated significantly within-session when a multimodal sensory stimulus of medium or high complexity was used but not when a unimodal sensory stimulus of low complexity was used. Finally, both the magnitude of sensation seeking and the magnitude of within-session escalation of sensation seeking were significantly greater in mice from the DBA/2J strain relative to mice from the C57BL/6J strain. Collectively, these findings indicate that stimulus complexity and genetic background drive escalation of operant sensation seeking within and across sessions, and that the BXD recombinant inbred mouse panel can be used to discover the genetic mechanisms underlying these phenomena

Sub-wavelength imaging at infrared frequencies using an array of metallic nanorods

We demonstrate that an array of metallic nanorods enables sub-wavelength (near-field) imaging at infrared frequencies. Using an homogenization approach, it is theoretically proved that under certain conditions the incoming radiation can be transmitted by the array of nanorods over a significant distance with fairly low attenuation. The propagation mechanism does not involve a resonance of material parameters and thus the resolution is not strongly affected by material losses and has wide bandwidth. The sub-wavelength imaging with $\lambda/10$ resolution by silver rods at 30 THz is demonstrated numerically using full-wave electromagnetic simulator.Comment: 12 pages, 16 figures, submitted to PR

Optical Hall Effect in the Integer Quantum Hall Regime

Optical Hall conductivity $\sigma_{xy}(\omega)$ is measured from the Faraday rotation for a GaAs/AlGaAs heterojunction quantum Hall system in the terahertz frequency regime. The Faraday rotation angle ($\sim$ fine structure constant $\sim$ mrad) is found to significantly deviate from the Drude-like behavior to exhibit a plateau-like structure around the Landau-level filling $\nu=2$. The result, which fits with the behavior expected from the carrier localization effect in the ac regime, indicates that the plateau structure, although not quantized, still exists in the terahertz regime.Comment: 4 pages, 4 figure

Generation and Evolution of Spin Entanglement in NRQED

A complete analysis on the generation of spin entanglement from NRQED is presented. The results of entanglement are obtained with relativistic correction to the leading order of (v/c)^2. It is shown that to this order the degree of entanglement of a singlet state does not change under time evolution whereas the triplet state can change.Comment: 8 pages, 1 figure, to appear in Phys. Rev.

Exciton-LO-phonon dynamics in InAs/GaAs quantum dots: Effects of zone-edge phonon damping

The dynamics of an exciton-LO-phonon system after an ultrafast optical excitation in an InAs/GaAs quantum dot is studied theoretically. Influence of anharmonic phonon damping and its interplay with the phonon dispersion is analyzed. The signatures of the zone-edge decay process in the absorption spectrum and time evolution are highlighted, providing a possible way of experimental investigation on phonon anharmonicity effects.Comment: 10 pages, 2 figure

Discovery of a Role for Rab3b in Habituation and Cocaine Induced Locomotor Activation in Mice Using Heterogeneous Functional Genomic Analysis

Substance use disorders are prevalent and present a tremendous societal cost but the mechanisms underlying addiction behavior are poorly understood and few biological treatments exist. One strategy to identify novel molecular mechanisms of addiction is through functional genomic experimentation. However, results from individual experiments are often noisy. To address this problem, the convergent analysis of multiple genomic experiments can discern signal from these studies. In the present study, we examine genetic loci that modulate the locomotor response to cocaine identified in the recombinant inbred (BXD RI) genetic reference population. We then applied the GeneWeaver software system for heterogeneous functional genomic analysis to integrate and aggregate multiple studies of addiction genomics, resulting in the identification o

Frequency-Dependent Squeezing for Advanced LIGO

The first detection of gravitational waves by the Laser Interferometer Gravitational-wave Observatory (LIGO) in 2015 launched the era of gravitational wave astronomy. The quest for gravitational wave signals from objects that are fainter or farther away impels technological advances to realize ever more sensitive detectors. Since 2019, one advanced technique, the injection of squeezed states of light is being used to improve the shot noise limit to the sensitivity of the Advanced LIGO detectors, at frequencies above $\sim 50$ Hz. Below this frequency, quantum back action, in the form of radiation pressure induced motion of the mirrors, degrades the sensitivity. To simultaneously reduce shot noise at high frequencies and quantum radiation pressure noise at low frequencies requires a quantum noise filter cavity with low optical losses to rotate the squeezed quadrature as a function of frequency. We report on the observation of frequency-dependent squeezed quadrature rotation with rotation frequency of 30Hz, using a 16m long filter cavity. A novel control scheme is developed for this frequency-dependent squeezed vacuum source, and the results presented here demonstrate that a low-loss filter cavity can achieve the squeezed quadrature rotation necessary for the next planned upgrade to Advanced LIGO, known as "A+."Comment: 6 pages, 2 figures, to be published in Phys. Rev. Let