Coding of visual object features and feature conjunctions in the human brain

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Induced gamma band responses predict recognition delays during object identification

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Induced gamma-band activity is related to the time point of object identification

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The integration of local chromatic motion signals is sensitive to contrast polarity

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Early and late effects of objecthood and spatial frequency on event-related potentials and gamma band activity

Background: The visual system may process spatial frequency information in a low-to-high, coarse-to-fine sequence. In particular, low and high spatial frequency information may be processed via different pathways during object recognition, with LSF information projected rapidly to frontal areas and HSF processed later in visual ventral areas. In an electroencephalographic study, we examined the time course of information processing for images filtered to contain different ranges of spatial frequencies. Participants viewed either high spatial frequency (HSF), low spatial frequency (LSF), or unfiltered, broadband (BB) images of objects or non-object textures, classifying them as showing either man-made or natural objects, or non-objects. Event-related potentials (ERPs) and evoked and total gamma band activity (eGBA and tGBA) recorded using the electroencephalogram were compared for object and non-object images across the different spatial frequency ranges. Results: The visual P1 showed independent modulations by object and spatial frequency, while for the N1 these factors interacted. The P1 showed more positive amplitudes for objects than non-objects, and more positive amplitudes for BB than for HSF images, which in turn evoked more positive amplitudes than LSF images. The peak-to-peak N1 showed that the N1 was much reduced for BB non-objects relative to all other images, while HSF and LSF non-objects still elicited as negative an N1 as objects. In contrast, eGBA was influenced by spatial frequency and not objecthood, while tGBA showed a stronger response to objects than non-objects. Conclusions: Different pathways are involved in the processing of low and high spatial frequencies during object recognition, as reflected in interactions between objecthood and spatial frequency in the visual N1 component. Total gamma band seems to be related to a late, probably high-level representational process

Ion-Driven Instabilities in the Inner Heliosphere II: Classification and Multi-Dimensional Mapping

Linear theory is a well developed framework for characterizing instabilities in weakly collisional plasmas, such as the solar wind. In the previous instalment of this series, we analyzed ~1.5M proton and alpha particle Velocity Distribution Functions (VDFs) observed by Helios I and II to determine the statistical properties of the standard instability parameters such as the growth rate, frequency, the direction of wave propagation, and the power emitted or absorbed by each component, as well as to characterize their behavior with respect to the distance from the Sun and collisional processing. In this work, we use this comprehensive set of instability calculations to train a Machine Learning algorithm consisting of three interlaced components that: 1) predict if an interval is unstable from observed VDF parameters; 2) predict the instability properties for a given unstable VDF; and 3) classify the type of the unstable mode. We use these methods to map the properties in multi-dimensional phase space to find that the parallel-propagating, proton-core-induced Ion Cyclotron mode dominates the young solar wind, while the oblique Fast Magnetosonic mode regulates the proton beam drift in the collisionally old plasma

PRIMING OF OBJECT CATEGORIZATION WITHIN AND ACROSS LEVELS OF SPECIFICITY

Identification of objects can occur at different levels of specificity. Dependingon task and context, an object can be classified at the superordinate level (as ananimal), at the basic level (a bird) or at the subordinate level (a sparrow). Whatare the interactions between these representational levels and do they rely onthe same sequential processes that lead to successful object identification? Inthis electroencephalogram study, a task-switching paradigm (covert naming orliving/non-living judgment) was used. Images of objects were repeated eitherwithin the same task, or with a switch from a covert naming task to a livingor non-living judgment and vice versa. While covert naming accesses entrylevel(basic or subordinate), living/non-living judgments rely on superordinateclassification. Our beha-vioural results demonstrated clear priming effectswithin both tasks. However, asymmetries were found when task-switching hadoccurred, with facilitation for covert naming but not for categorization. Wealso found lower accuracy and early-starting and persistent enhancements ofevent-related potentials (ERPs) for covert naming, indicating that this task wasmore difficult and involved more intense perceptual and semantic processing.Perceptual priming was marked by consistent reductions of the ERP componentL1 for repeated presentations, both with and without task switching. Additionalrepetition effects were found in early event-related activity between 150-190 ms(N1) when a repeated image had been named at initial presentation. We conclude that differences in N1 indicate task-related changes in the identification processitself. Such enhancements for covert naming again emerge in a later timewindow associated with depth of semantic processing. Meanwhile, L1 reflectsmodulations due to implicit memory of objects. In conclusion, evidence wasfound for representational overlap; changes in ERP markers started early andrevealed cross-task priming at the level of object structure analysis and moreintense perceptual and semantic processing for covert naming

Induced Gamma-band Activity Elicited by Visual Representation of Unattended Objects

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The evolution of home detention based sanctions frameworks in the USA and Australia up to 2013: a comparative case study

Contemporary Home Detention Based Sanctions (HDBS), which utilise electronic monitoring (EM) technology, became first available in the 1980s in the United States of America (USA). While the development and expansion of contemporary HDBS throughout the world has taken place over the last three decades (1982-2013) with varied success, relatively little is known about their comparative rationale, implementation and operation. The employment of comparative historical scholarship in this study of HDBS has allowed the researcher to identify and examine the similarities and differences in the development, operation and outcomes of HDBS over time (last three decades, that is, from 1982 to 2013) and place (the USA and Australia). More broadly, the evolution of the HDBS frameworks in this research has been divided into three ideologically distinguishable phases. The early phase of HDBS in the USA and Australia occurred from 1840s until the 1960s. Following this, the middle phase of HDBS occurred in the USA and Australia from the 1960s to 1970s. It comprised five converging factors. This culminated in a ‘correctional disillusion’ that led to governments’ decisions to introduce the late phase of HDBS, which has been operational over the last three decades (1982-2013). The late phase of HDBS in the USA commenced with the implementation of intermediate sanctions, comprising of HDBS with Radio Frequency (RF) in the 1980s. In the mid-2000s, however, the expansion of sex offender post-release supervision laws and the development of electronically monitored Global Positioning Systems (GPS) technology led to utilisation HDBS for serious sex offenders. The last three decades of evaluative research about HDBS with RF have generally indicated problematic operational outcomes as well as significant ethical and political and stakeholder issues and dilemmas. On the other hand, HDBS with GPS have been operationally successful, although studies assessing some of their ethical and overall political and stakeholder issues and dilemmas have been lacking. The late phase of HDBS with RF in Australia also started in the 1980s. HDBS with GPS entered the correctional arena after 2000 in very similar circumstances to the USA. The last three decades of evaluative research of HDBS with RF have generally found that these sanctions have achieved their anticipated operational results, but have encompassed significant ethical and particularly political and stakeholder issues and dilemmas. Research assessing the operational outcomes, ethical and political and stakeholder issues and dilemmas of HDBS with GPS is still inadequate, and it is imperative that such research is conducted in the future. The predicted future trajectory of HDBS in both the USA and Australia is increased sanction application. The future viability and outcomes of HDBS in both nation states are however dependent on whether policy makers and/or correctional administrators, with the support of governments, improve the operation of HDBS by implementing the lessons learnt based on the evidence of best practice. If the jurisdictions within the USA and Australia implement the specific lessons learnt relevant to their own problematic areas of HDBS’ operation, the application of these sanctions will become more effective

S-cone signals invisible to the motion system can improve motion extraction via grouping by color

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