The functional effects of modal versus amodal filling-in

Comparisons between modally and amodally completed regions show that perceptual filling-in is not merely the ignoring of absences. Illusory filled-in colour arises for modal completion, but not for amodal completion in comparable displays. We find that attention spreads automatically to modally but not amodally completed regions from their inducers, revealing a functional effect of filled-in colour

Production Constraints and the NAIRU

This paper argues that the production constraints in the basic NAIRU model should be distinguished by type: capital constraints and labour constraints. It notes the failure to incorporate this phenomenon in standard macro models. Using panel data for UK manufacturing over 80 quarters we show that capital constraints became relatively more important during the 1980s as industry failed to match the increase in labour flexibility with rising capital investment

Quantifying cosmic variance

We determine an expression for the cosmic variance of any "normal" galaxy survey based on examination of M* +/- 1 mag galaxies in the SDSS DR7 data cube. We find that cosmic variance will depend on a number of factors principally: total survey volume, survey aspect ratio, and whether the area surveyed is contiguous or comprised of independent sight-lines. As a rule of thumb cosmic variance falls below 10% once a volume of 10^7h_0.7^-3Mpc^3 is surveyed for a single contiguous region with a 1:1 aspect ratio. Cosmic variance will be lower for higher aspect ratios and/or non-contiguous surveys. Extrapolating outside our test region we infer that cosmic variance in the entire SDSS DR7 main survey region is ~7% to z < 0.1. The equation obtained from the SDSS DR7 region can be generalised to estimate the cosmic variance for any density measurement determined from normal galaxies (e.g., luminosity densities, stellar mass densities and cosmic star-formation rates) within the volume range 10^3 to 10^7 h^-3_0.7Mpc^3. We apply our equation to show that 2 sightlines are required to ensure cosmic variance is <10% in any ASKAP galaxy survey (divided into dz ~0.1 intervals, i.e., ~1 Gyr intervals for z <0.5). Likewise 10 MeerKAT sightlines will be required to meet the same conditions. GAMA, VVDS, and zCOSMOS all suffer less than 10% cosmic variance (~3%-8%) in dz intervals of 0.1, 0.25, and 0.5 respectively. Finally we show that cosmic variance is potentially at the 50-70% level, or greater, in the HST Ultra Deep Field depending on assumptions as to the evolution of clustering. 100 or 10 independent sightlines will be required to reduce cosmic variance to a manageable level (<10%) for HST ACS or HST WFC3 surveys respectively (in dz ~ 1 intervals). Cosmic variance is therefore a significant factor in the z>6 HST studies currently underway.Comment: Accepted for publication in MNRA

The cutaneous 'rabbit' illusion affects human primary sensory cortex somatopically

We used functional magnetic resonance imaging (fMRI) to study neural correlates of a robust somatosensory illusion that can dissociate tactile perception from physical stimulation. Repeated rapid stimulation at the wrist, then near the elbow, can create the illusion of touches at intervening locations along the arm, as if a rabbit hopped along it. We examined brain activity in humans using fMRI, with improved spatial resolution, during this version of the classic cutaneous rabbit illusion. As compared with control stimulation at the same skin sites (but in a different order that did not induce the illusion), illusory sequences activated contralateral primary somatosensory cortex, at a somatotopic location corresponding to the filled-in illusory perception on the forearm. Moreover, the amplitude of this somatosensory activation was comparable to that for veridical stimulation including the intervening position on the arm. The illusion additionally activated areas of premotor and prefrontal cortex. These results provide direct evidence that illusory somatosensory percepts can affect primary somatosensory cortex in a manner that corresponds somatotopically to the illusory percept

The Millennium Galaxy Catalogue: Star counts and the Structure of the Galactic Stellar Halo

We derive a star catalogue generated from the images taken as part of the 37.5 sq. deg Millennium Galaxy Catalogue. These data, alone and together with colours gained from the Sloan Digital Sky Survey Early Data Release, allow the analysis of faint star counts (B(MGC) < 20) at high Galactic latitude (41 < b < 63), as a function of Galactic longitude (239 < l < 353). We focus here on the inner stellar halo, providing robust limits on the amplitude of substructure and on the large-scale flattening. In line with previous results, the thick disk, an old, intermediate-metallicity population, is clearly seen in the colour-magnitude diagram. We find that the Galactic stellar halo within ~10 kpc (the bulk of the stellar mass) is significantly flattened, with an axial ratio of (c/a) =0.56 +/- 0.01, again consistent with previous results. Our analysis using counts-in-cells, angular correlation functions and the Lee 2D statistic, confirms tidal debris from the Sagittarius dwarf but finds little evidence for other substructure in the inner halo, at heliocentric distances of < 5 kpc. This new quantification of the smoothness in coordinate space limits the contribution of recent accretion/disruption to the build-up of the bulk of the stellar halo.Comment: Accepted for publication in MNRAS (figs 16 and 17 degraded here

Object-guided Spatial Attention in Touch: Holding the Same Object with Both Hands Delays Attentional Selection

Abstract Previous research has shown that attention to a specific location on a uniform visual object spreads throughout the entire object. Here we demonstrate that, similar to the visual system, spatial attention in touch can be object guided. We measured event-related brain potentials to tactile stimuli arising from objects held by observers' hands, when the hands were placed either near each other or far apart, holding two separate objects, or when they were far apart but holding a common object. Observers covertly oriented their attention to the left, to the right, or to both hands, following bilaterally presented tactile cues indicating likely tactile target location(s). Attentional modulations for tactile stimuli at attended compared to unattended locations were present in the time range of early somatosensory components only when the hands were far apart, but not when they were near. This was found to reflect enhanced somatosensory processing at attended locations rather than suppressed processing at unattended locations. Crucially, holding a common object with both hands delayed attentional selection, similar to when the hands were near. This shows that the proprioceptive distance effect on tactile attentional selection arises when distant event locations can be treated as separate and unconnected sources of tactile stimulation, but not when they form part of the same object. These findings suggest that, similar to visual attention, both space- and object-based attentional mechanisms can operate when we select between tactile events on our body surface.</jats:p