Circuits for local and global signal integration in primary visual cortex

Journal ArticleContrast-dependent changes in spatial summation and contextual modulation of primary visual cortex (V1) neuron responses to stimulation of their receptive field reveal long-distance integration of visual signals within V1, well beyond the classical receptive field (cRF) of single neurons. To identify the cortical circuits mediating these long-distance computations, we have used a combination of anatomical and physiological recording methods to determine the spatial scale and retinotopic logic of intra-areal V1 horizontal connections and inter-areal feedback connections to V1. We have then compared the spatial scales of these connectional systems to the spatial dimensions of the cRF, spatial summation field (SF), and modulatory surround field of macaque V1 neurons. We find that monosynaptic horizontal connections within area V1 are of an appropriate spatial scale to mediate interactions within the SF of V1 neurons and to underlie contrast-dependent changes in SF size. Contrary to common beliefs, these connections cannot fully account for the dimensions of the surround field. The spatial scale of feedback circuits from extrastriate cortex to V1 is, instead, commensurate with the full spatial range of center-surround interactions. Thus these connections could represent an anatomical substrate for contextual modulation and global-to-local integration of visual signals. Feedback projections connect corresponding and equal-sized regions of the visual field in striate and extrastriate cortices and cover anisotropic parts of visual space, unlike V1 horizontal connections that are isotropic in the macaque. V1 isotropic connectivity demonstrates that anisotropic horizontal connections are not necessary to generate orientation selectivity. Anisotropic feedback connections may play a role in contour completion

Standoff Detection via Single-Beam Spectral Notch Filtered Pulses

We demonstrate single-beam coherent anti-Stokes Raman spectroscopy (CARS), for detecting and identifying traces of solids, including minute amounts of explosives, from a standoff distance (>50 m) using intense femtosecond pulses. Until now, single-beam CARS methods relied on pulse-shapers in order to obtain vibrational spectra. Here we present a simple and easy-to-implement detection scheme, using a commercially available notch filter, that does not require the use of a pulse-shaper.Comment: 3 pages, 3 figure

What is the optimal number of researchers for social science research?

Many studies have found that co-authored research is more highly cited than single author research. This finding is policy relevant as it indicates that encouraging co-authored research will tend to maximise citation impact. Nevertheless, whilst the citation impact of research increase as the number of authors increases in the sciences, the extent to which this occurs in the social sciences is unknown. In response, this study investigates the average citation level of articles with one to four authors published in 1995, 1998, 2001, 2004 and 2007 in 19 social science disciplines. The results suggest that whilst having at least two authors gives a substantial citation impact advantage in all social science disciplines, additional authors are beneficial in some disciplines but not in others.University of Wolverhampto

Developing a model of disability that focuses on the actions of disabled people

Disabled people, writers on disability and disability activists stress the importance of disabled people being included in all aspects of society. I argue that a major omission from this inclusiveness, is that no current model of disability focuses on the impact of the actions of disabled people on disability. Disabled people are not passive bystanders, powerless to reduce the restrictions of disability. On the contrary, we are central to actively limiting its constraints. I develop a model of disability, called ‘active’, which focuses on the effects on disability of the individual and collective actions of disabled people. I describe published findings which indicate that engaging in self-help, using support groups and deploying assistive technology can all reduce the limitations of disability. Recent increases in the number of disability support groups and developments in assistive technology have substantially augmented the potential for disabled people to combat the effects of disability

A First Principles Theory of Nuclear Magnetic Resonance J-Coupling in solid-state systems

A method to calculate NMR J-coupling constants from first principles in extended systems is presented. It is based on density functional theory and is formulated within a planewave-pseudopotential framework. The all-electron properties are recovered using the projector augmented wave approach. The method is validated by comparison with existing quantum chemical calculations of solution-state systems and with experimental data. The approach has been applied to verify measured J-coupling in a silicophosphate structure, Si5O(PO4)6Comment: 9 page

Arbitrary precision composite pulses for NMR quantum computing

We discuss the implementation of arbitrary precision composite pulses developed using the methods of Brown et al. [Phys. Rev. A 70 (2004) 052318]. We give explicit results for pulse sequences designed to tackle both the simple case of pulse length errors and for the more complex case of off-resonance errors. The results are developed in the context of NMR quantum computation, but could be applied more widely.Comment: 16 pages elsart, no figures. In press at Journal of Magnetic resonanc

Automated Biochemical, Morphological, and Organizational Assessment of Precancerous Changes from Endogenous Two-Photon Fluorescence Images

Multi-photon fluorescence microscopy techniques allow for non-invasive interrogation of live samples in their native environment. These methods are particularly appealing for identifying pre-cancers because they are sensitive to the early changes that occur on the microscopic scale and can provide additional information not available using conventional screening techniques.In this study, we developed novel automated approaches, which can be employed for the real-time analysis of two-photon fluorescence images, to non-invasively discriminate between normal and pre-cancerous/HPV-immortalized engineered tissues by concurrently assessing metabolic activity, morphology, organization, and keratin localization. Specifically, we found that the metabolic activity was significantly enhanced and more uniform throughout the depths of the HPV-immortalized epithelia, based on our extraction of the NADH and FAD fluorescence contributions. Furthermore, we were able to separate the keratin contribution from metabolic enzymes to improve the redox estimates and to use the keratin localization as a means to discriminate between tissue types. To assess morphology and organization, Fourier-based, power spectral density (PSD) approaches were employed. The nuclear size distribution throughout the epithelial depths was quantified by evaluating the variance of the corresponding spatial frequencies, which was found to be greater in the normal tissue compared to the HPV-immortalized tissues. The PSD was also used to calculate the Hurst parameter to identify the level of organization in the tissues, assuming a fractal model for the fluorescence intensity fluctuations within a field. We found the range of organization was greater in the normal tissue and closely related to the level of differentiation.A wealth of complementary morphological, biochemical and organizational tissue parameters can be extracted from high resolution images that are acquired based entirely on endogenous sources of contrast. They are promising diagnostic parameters for the non-invasive identification of early cancerous changes and could improve significantly diagnosis and treatment for numerous patients

Irradiation-Mediated Rescue of T Cell–Specific V(D)j Recombination and Thymocyte Differentiation in Severe Combined Immunodeficient Mice by Bone Marrow Cells

In SCID (severe combined immunodeficient) mice, proper assembly of immunoglobulin and T cell receptor (TCR) genes is blocked by defective V(D)J recombination so that B and T lymphocyte differentiation is arrested at an early precursor stage. Treating the mice with gamma irradiation rescues V(D)J rearrangement at multiple TCR loci, promotes limited thymocyte differentiation, and induces thymic lymphomas. These effects are not observed in the B cell lineage. Current models postulate that irradiation affects intrathymic T cell precursors. Surprisingly, we found that transfer of irradiated SCID bone marrow cells to unirradiated host animals rescues both TCR rearrangements and thymocyte differentiation. These data indicate that irradiation affects precursor cells at an earlier stage of differentiation than was previously thought and suggest new models for the mechanism of irradiation rescue

Retweeting Covid-19 disability issues: Risks, support and outrage

© 2020 The Authors. Published by El Profesional de la Información. This is an open access article available under a Creative Commons licence. The published version can be accessed at the following link on the publisher’s website: https://doi.org/10.3145/epi.2020.mar.16The Covid-19 pandemic has greatly uneven impacts on sectors of society. People with disabilities are particularly vulnerable to it and so it is important to understand both the disability perspective and the role of social media. This information may help to reduce the risk from the disease. In response, this article uses thematic analysis to investigate 59 disability-related tweets from March 10 to April 4, 2020 that were retweeted at least 500 times, with a quarter of a million retweets altogether. This approach generates quick insights into widely resonating disability-related issues. The results suggest the value of Twitter for disseminating information about the risk, offers or requests for support, the ability of many people with disabilities to adjust to the changes well, and information about individuals with the disease. In addition, there was outrage at suggestions that the disease was less serious because young people without disabilities were relatively low risk, and that people with disabilities might be denied equal access to medical treatment. As one tweet pointed out, people in less vulnerable categories should not be told on Twitter or elsewhere that the disease is less relevant to them because their actions can impact others through social spreading.Published onlin