Subthalamic responses to motor cortex stimulation:Selective targeting of the subthalamic motor area

Introduction: Over the last decades, it has been shown consistently that deep brain stimulation (DBS) of the subthalamic nucleus (STN) alleviates motor symptoms in Parkinson (PD) patients. However, in a substantial number of patients the beneficial effects of STN DBS are overshadowed by cognitive and/or limbic alterations. These side effects of STN DBS are thought to be caused by stimulation of the associative and limbic pathways that run through the STN. We hypothesize that an optimal effect of STN DBS on the motor symptoms without inducing cognitive and limbic side effects can be achieved by selective stimulation of the STN motor region by improved targeting. To achieve this goal, we made use of the cortico-subthalamic projection. We hypothesize that in PD patients motor cortex stimulation (MCS) evokes a specific response in the dorsolateral part of the STN, supposedly the STN motor area, that can be seen in both single unit activity and local field potentials (LFP). Material and Methods: Here we describe the results of one PD patient in which we performed MCS during the intra-operative STN microrecordings. In total, we measured single unit activity of eight neurons at various locations in the STN and LFP’s at the same locations. Data were analyzed using Matlab. All recordings were high pass filtered, the stimulus artifact was removed by time shifting, peristimulus time histograms were constructed from which significant excitatory and inhibitory responses were determined using the change point analysis. Results: The STN neurons had an average spontaneous firing rate of 64.6±36.3 Hz. Within the STN responses to MCS were seen, while outside the borders of the STN no responses were found. Responses differed between ventro-dorsal regions in the anterior-posterior and medio-lateral plane. In the anterior and lateral electrode at dorsal levels of the STN a significant early excitation (~10-50ms) and subsequent inhibition (50-110ms) were seen. The lateral electrode also showed a late excitation (~115-170ms). The responses we found were partially similar to reports in animal studies, but we did not observe the typical triphasic response. Conclusion: We found responses in the STN during MCS, which were significantly different in the dorsally recorded neurons in the lateral and anterior trajectory compared to the neurons recorded in other regions of the STN. In the near future MCS could be a novel tool to determine the motor area of the STN to optimize targeting for DBS in PD patients, thereby preventing cognitive and limbic side effect

Феномен мастурбации: негативное или позитивное явление?

Рассмотрены разные взгляды на роль мастурбации в становлении сексуальности человека. Представлены результаты собственных исследований автора, проведенных с целью установить значение этого феномена для формирования сексуального поведения и сексуального здоровья.Various opinions about the role of masturbation in human sexuality development are discussed. The findings of the original research performed to evaluate the significance of this phenomenon in formation of sexual behavior and sexual health are reported

Magnetotunneling Between Two-dimensional Electron Gases in InAs-AlSb-GaSb Heterostructures

We have observed that the tunneling magnetoconductance between two-dimensional (2D) electron gases formed at nominally identical InAs-AlSb interfaces most often exhibits two sets of Shubnikov-de Haas oscillations with almost the same frequency. This result is explained quantitatively with a model of the conductance in which the 2D gases have different densities and can tunnel between Landau levels with different quantum indices. When the epitaxial growth conditions of the interfaces are optimized, the zero-bias magnetoconductance shows a single set of oscillations, thus proving that the asymmetry between the two electron gases can be eliminated.Comment: RevTeX format including 4 figures; submit for publicatio

Andreev Reflection in Strong Magnetic Fields

We have studied the interplay of Andreev reflection and cyclotron motion of quasiparticles at a superconductor-normal-metal interface with a strong magnetic field applied parallel to the interface. Bound states are formed due to the confinement introduced both by the external magnetic field and the superconducting gap. These bound states are a coherent superposition of electron and hole edge excitations similar to those realized in finite quantum-Hall samples. We find the energy spectrum for these Andreev edge states and calculate transport properties.Comment: 5 pages, 3 figures, RevTex, revised to include more detailed discussion of currents and transpor

Ballistic spin-polarized transport and Rashba spin precession in semiconductor nanowires

We present numerical calculations of the ballistic spin-transport properties of quasi-one-dimensional wires in the presence of the spin-orbit (Rashba) interaction. A tight-binding analog of the Rashba Hamiltonian which models the Rashba effect is used. By varying the robustness of the Rashba coupling and the width of the wire, weak and strong coupling regimes are identified. Perfect electron spin-modulation is found for the former regime, regardless of the incident Fermi energy and mode number. In the latter however, the spin-conductance has a strong energy dependence due to a nontrivial subband intermixing induced by the strong Rashba coupling. This would imply a strong suppression of the spin-modulation at higher temperatures and source-drain voltages. The results may be of relevance for the implementation of quasi-one-dimensional spin transistor devices.Comment: 19 pages (incl. 9 figures). To be published in PR

PosMed (Positional Medline): prioritizing genes with an artificial neural network comprising medical documents to accelerate positional cloning

PosMed (http://omicspace.riken.jp/) prioritizes candidate genes for positional cloning by employing our original database search engine GRASE, which uses an inferential process similar to an artificial neural network comprising documental neurons (or ‘documentrons’) that represent each document contained in databases such as MEDLINE and OMIM. Given a user-specified query, PosMed initially performs a full-text search of each documentron in the first-layer artificial neurons and then calculates the statistical significance of the connections between the hit documentrons and the second-layer artificial neurons representing each gene. When a chromosomal interval(s) is specified, PosMed explores the second-layer and third-layer artificial neurons representing genes within the chromosomal interval by evaluating the combined significance of the connections from the hit documentrons to the genes. PosMed is, therefore, a powerful tool that immediately ranks the candidate genes by connecting phenotypic keywords to the genes through connections representing not only gene–gene interactions but also other biological interactions (e.g. metabolite–gene, mutant mouse–gene, drug–gene, disease–gene and protein–protein interactions) and ortholog data. By utilizing orthologous connections, PosMed facilitates the ranking of human genes based on evidence found in other model species such as mouse. Currently, PosMed, an artificial superbrain that has learned a vast amount of biological knowledge ranging from genomes to phenomes (or ‘omic space’), supports the prioritization of positional candidate genes in humans, mouse, rat and Arabidopsis thaliana

Interaction-Induced Enhancement of Spin-Orbit Coupling in Two-Dimensional Electronic System

We study theoretically the renormalization of the spin-orbit coupling constant of two-dimensional electrons by electron-electron interactions. We demonstrate that, similarly to the $g$ factor, the renormalization corresponds to the enhancement, although the magnitude of the enhancement is weaker than that for the $g$ factor. For high electron concentrations (small interaction parameter $r_s$) the enhancement factor is evaluated analytically within the static random phase approximation. For large $r_s\sim 10$ we use an approximate expression for effective electron-electron interaction, which takes into account the local field factor, and calculate the enhancement numerically. We also study the interplay between the interaction-enhanced Zeeman splitting and interaction-enhanced spin-orbit coupling.Comment: 18 pages, 2 figures, REVTe

Long-term cardiometabolic disease risk in women with PCOS:a systematic review and meta-analysis

BACKGROUND: Polycystic ovary syndrome (PCOS) is associated with cardiometabolic disease, but recent systematic reviews and meta-analyses of longitudinal studies that quantify these associations are lacking. OBJECTIVE AND RATIONALE: Is PCOS a risk factor for cardiometabolic disease? SEARCH METHODS: We searched from inception to September 2019 in MEDLINE and EMBASE using controlled terms (e.g. MESH) and text words for PCOS and cardiometabolic outcomes, including cardiovascular disease (CVD), stroke, myocardial infarction, hypertension (HT), type 2 diabetes (T2D), metabolic syndrome and dyslipidaemia. Cohort studies and case-control studies comparing the prevalence of T2D, HT, fatal or non-fatal CVD and/or lipid concentrations of total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C) and triglycerides (TGs) between women with and without PCOS of ≥18 years of age were eligible for this systematic review and meta-analysis. Studies were eligible regardless of the degree to which they adjusted for confounders including obesity. Articles had to be written in English, German or Dutch. Intervention studies, animal studies, conference abstracts, studies with a follow-up duration less than 3 years and studies with less than 10 PCOS cases were excluded. Study selection, quality assessment (Newcastle-Ottawa Scale) and data extraction were performed by two independent researchers. OUTCOMES: Of the 5971 identified records, 23 cohort studies were included in the current systematic review. Women with PCOS had increased risks of HT (risk ratio (RR): 1.75, 95% CI 1.42 to 2.15), T2D (RR: 3.00, 95% CI 2.56 to 3.51), a higher serum concentration of TC (mean difference (MD): 7.14 95% CI 1.58 to 12.70 mg/dl), a lower serum concentration of HDL-C (MD: -2.45 95% CI -4.51 to -0.38 mg/dl) and increased risks of non-fatal cerebrovascular disease events (RR: 1.41, 95% CI 1.02 to 1.94) compared to women without PCOS. No differences were found for LDL-C (MD: 3.32 95% CI -4.11 to 10.75 mg/dl), TG (MD 18.53 95% CI -0.58 to 37.64 mg/dl) or coronary disease events (RR: 1.78, 95% CI 0.99 to 3.23). No meta-analyses could be performed for fatal CVD events due to the paucity of mortality data. WIDER IMPLICATIONS: Women with PCOS are at increased risk of cardiometabolic disease. This review quantifies this risk, which is important for clinicians to inform patients and to take into account in the cardiovascular risk assessment of women with PCOS. Future clinical trials are needed to assess the ability of cardiometabolic screening and management in women with PCOS to reduce future CVD morbidity

Dissipation effects in spin-Hall transport of electrons and holes

We investigate the spin-Hall effect of both electrons and holes in semiconductors using the Kubo formula in the correct zero-frequency limit taking into account the finite momentum relaxation time of carriers in real semiconductors. This approach allows to analyze the range of validity of recent theoretical findings. In particular, the spin-Hall conductivity vanishes for vanishing spin-orbit coupling if the correct zero-frequency limit is performed.Comment: 5 pages, no figures, version to appear in Phys. Rev.

Anisotropic transport in the two-dimensional electron gas in the presence of spin-orbit coupling

In a two-dimensional electron gas as realized by a semiconductor quantum well, the presence of spin-orbit coupling of both the Rashba and Dresselhaus type leads to anisotropic dispersion relations and Fermi contours. We study the effect of this anisotropy on the electrical conductivity in the presence of fixed impurity scatterers. The conductivity also shows in general an anisotropy which can be tuned by varying the Rashba coefficient. This effect provides a method of detecting and investigating spin-orbit coupling by measuring spin-unpolarized electrical currents in the diffusive regime. Our approach is based on an exact solution of the two-dimensional Boltzmann equation and provides also a natural framework for investigating other transport effects including the anomalous Hall effect.Comment: 10 pages, 1 figure included. Discussion of experimental impact enlarged; error in calculation of conductivity contribution corrected (cf. Eq. (A14)), no changes in qualitative results and physical consequence