Contextual modulation of primary visual cortex by auditory signals.

Early visual cortex receives non-feedforward input from lateral and top-down connections (Muckli & Petro 2013 Curr. Opin. Neurobiol. 23, 195-201. (doi:10.1016/j.conb.2013.01.020)), including long-range projections from auditory areas. Early visual cortex can code for high-level auditory information, with neural patterns representing natural sound stimulation (Vetter et al. 2014 Curr. Biol. 24, 1256-1262. (doi:10.1016/j.cub.2014.04.020)). We discuss a number of questions arising from these findings. What is the adaptive function of bimodal representations in visual cortex? What type of information projects from auditory to visual cortex? What are the anatomical constraints of auditory information in V1, for example, periphery versus fovea, superficial versus deep cortical layers? Is there a putative neural mechanism we can infer from human neuroimaging data and recent theoretical accounts of cortex? We also present data showing we can read out high-level auditory information from the activation patterns of early visual cortex even when visual cortex receives simple visual stimulation, suggesting independent channels for visual and auditory signals in V1. We speculate which cellular mechanisms allow V1 to be contextually modulated by auditory input to facilitate perception, cognition and behaviour. Beyond cortical feedback that facilitates perception, we argue that there is also feedback serving counterfactual processing during imagery, dreaming and mind wandering, which is not relevant for immediate perception but for behaviour and cognition over a longer time frame.This article is part of the themed issue 'Auditory and visual scene analysis'.

Long gamma-ray bursts and core-collapse supernovae have different environments.

When massive stars exhaust their fuel, they collapse and often produce the extraordinarily bright explosions known as core-collapse supernovae. On occasion, this stellar collapse also powers an even more brilliant relativistic explosion known as a long-duration gamma-ray burst. One would then expect that these long gamma-ray bursts and core-collapse supernovae should be found in similar galactic environments. Here we show that this expectation is wrong. We find that the gamma-ray bursts are far more concentrated in the very brightest regions of their host galaxies than are the core-collapse supernovae. Furthermore, the host galaxies of the long gamma-ray bursts are significantly fainter and more irregular than the hosts of the core-collapse supernovae. Together these results suggest that long-duration gamma-ray bursts are associated with the most extremely massive stars and may be restricted to galaxies of limited chemical evolution. Our results directly imply that long gamma-ray bursts are relatively rare in galaxies such as our own Milky Way.

Using entropies of reaction to predict changes in protein stability: tyrosine-67-phenylalanine variants of rat cytochrome c and yeast Iso-1 cytochromes c.

Using the voltammetric method of square-wave voltammetry, a direct electrochemical examination was made of the wild type and Tyr67Phe mutant of both rat cytochrome c and yeast iso-1-cytochrome c. In addition to determining the equilibrium reduction potential (E0') for each cytochrome, the entropy of reaction, deltaS0'(Rxn)(deltaS0'(Rxn) = S0'(Red) - S0'(Ox)), for the reduction process was determined via the non-isothermal method. Having determined deltaS0'(Rxn) and E0', deltaH0' was calculated. For rat cytochrome c, it was found that deltaS0'(Rxn) = -43 J mol(-1) K(-1) for the wild type and -53 J mol(-1) K(-1) for the Tyr67Phe variant, with the deltaH0' for both the wild type and variant nearly identical, indicating that the changes in reduction potential and probably stability are due to changes in deltaS0'(Rxn). In contrast the measured deltaS0'(Rxn) for yeast iso-1-cytochrome c demonstrated significant changes in both entropic and enthalpic contributions in going from wild type to mutant cytochrome c. The entropy of reaction provides information regarding the relative degree of solvation, and very likely the degree of compactness, of the oxidized state versus the reduced state of the redox protein. A thermodynamic scheme and stability derivation are presented that show how the entropies of reaction of wild type versus variant cytochromes contribute to and predict changes in stability in going from oxidized to reduced protein. For yeast iso-1-cytochrome c, the thermodynamically predicted change in stability was very close to the experimentally observed value, based on previous differential scanning calorimetric stability measurements. While such data is not available for rat cytochrome c, consideration of the enormously increased local stability of the rat oxidized cytochrome c variant predicts that the reduced rat variant will be even more stable than the already stabilized oxidized variant.

Pulmonary aspiration in mechanically ventilated patients with tracheostomies.

The purpose of this descriptive study was to evaluate feeding aspirations in adult patients receiving long-term mechanical ventilatory support, including the incidence of aspirations, the frequency of silent (clinically inapparent) aspirations, and differences between aspirators and nonaspirators. Aspiration data were determined by review of videofluoroscopic (VF) tapes of modified barium swallow procedures performed on 83 medically stable patients admitted to a chronic ventilator unit. Demographic and clinical variables were obtained from review of subjects' medical records. Forty-two subjects (50 percent) aspirated during VF testing and 37 of 48 (77 percent) aspirations were silent. Subjects who aspirated were significantly older than those who did not aspirate (p = 0.007). Swallowing disorders were common, particularly disturbances of the pharyngeal phase. We conclude that feeding aspiration is seen frequently in patients with tracheostomies receiving prolonged positive pressure mechanical ventilation. Advanced age increases the risk of aspiration in this population. Episodes of aspiration are not consistently accompanied by clinical symptoms of distress to alert the bedside observer to their occurrence.

The accountability of incest offenders.

Child victims of incest further victimization if offenders are not brought to justice. Cultural factors that inhibit the reporting of offenders are discussed. The work of Prescott House, Jefferson County, Alabama, an interview site for child victims of incest, is described. All those concerned with child abuse in a community should collaborate to find and prosecute offenders.