Flexible cortical gamma-band correlations suggest neural principles of visual processing

We summarize recent studies of our group from the primary visual cortex V1 of behaving monkeys referring to the hypothesis of spatial feature binding by γ-synchronization (30-90 Hz). In agreement with this hypothesis the data demonstrates decoupling of γ-activities among neural groups representing figure and ground. As γ-synchronization in V1 is restricted to cortical ranges of few millimeters, feature binding may equivalently be restricted in visual space. Closer inspection shows that the restriction in synchrony is due to far-reaching travelling γ-waves with changing phase coupling. Based on this observation we extend the initial binding-by-synchronization hypothesis and suggest object continuity to be coded by phase continuity. It is further argued that the spatial phase changes of the V1 γ-waves in general will also limit lateral phase coupling to higher levels of processing. Instead of phase-locked γ-coupling, corticocortical cooperation among γ-processes may be mediated by mutual amplitude modulations that are more reliable than phase synchrony over larger distances. The relevance of this concept of corticocortical binding is demonstrated with subdural recordings from human subjects performing cognitive tasks. The experimental results are discussed on the basis of network models with spiking neurons.     

Neural Mechanisms of Visual Feature Binding Investigated with Microelectrodes and Models

A single object generally activates neurones in many visual cortical areas corresponding to a distributed representation of its features. Itis still under debate how the distributed representation of an objectis bound intoa coherent whole and how unrelated features are separated. Synchronization of neural signals has been proposed to code spatial feature binding, supported by the discovery of synchronized assemblies in visual cortex. Synchronizations are either fast oscillatory (30–90 Hz) cortically generated events, or non-rhythmical stimulus-locked responses, depending on the visual stimulation. The cortical range over which synchronizations occur, transformed to visual space, is generally several times larger than the classical receptive fields (CRF) of neurones in lower visual cortex areas. However, the cortical regions synchronized by fastoscillations do notspan the representational range of larger objects but only parts of it. To relate such restricted segments to perceptual processes the concept of the association field (AF) of local neural assemblies was introduced in accordance with CRFs of single neurones. Here an AF is composed of the aggregate of CRFs of an assembly engaged in a common synchronized state. Itis argued thatspatial continuity of an object is coded by a continuum of overlapping AFs, that is, by overlapping regions of phase coupled neurones. Hence, object continuity would be represented by phase continuity. Besides feature binding, feature separation is necessary for scene segmentation. Separation may be coded by functional decoupling causing uncorrelated activities or by mutual inhibition leading to alternating activations in assemblies of separate representations. A third temporal coding aspect is temporal segmentation by the shortactivation-inhibition cycles of fast oscillations orshorttransientstimulus-locked responses, which may preventperceptual “smearing” by interrupting the flow of visual information into precisely defined frames. The presentpaperalso aims atrelating signals of stimulus dependentsynchronization and desynchronization with basic neural mechanisms and circuits. Finally, the synchronization hypothesis is critically discussed with respect to contradictory psychophysical work and supportive new recording results, including evidence for perception-related synchronizations.     

It's not what you are,it's what you know: experience,beliefs, and the detection of deception in employment interviews

This study investigated the ability of more or less experienced employment interviewers and laypersons to detect deception in employment interviews. Although correct beliefs about indicators of deception led to higher deception detection accuracy, more experienced employment interviewers did not show more accurate beliefs about indicators of deception and did not perform better at detecting deception than less experienced interviewers and laypersons. Furthermore, more experienced interviewers showed a less‐pronounced tendency of judging messages as true irrespective of their actual truthfulness (truth bias) than less experienced interviewers and laypersons. It is suggested that experience in employment interviewing does not automatically lead to higher deception detection abilities in employment interviews, but that correcting people's beliefs about indicators of deception can do so.     

Set representations of orders and a structural equivalent of saturation

Set representations are useful in the theory of knowledge spaces. A set representation of an order is an isomorphic mapping of its base set into the power set of some set ordered by set inclusion. Such a representation is basic if the union of the representing sets of the predecessors of an element contains strictly less elements than the representing set of this element, and it is parsimonious if the difference is exactly one element. This paper investigates the properties of the minimal number of elements which must be used in a parsimonious representation. This value is studied for several order operations. Moreover, orders which allow essentially only one parsimonious set representation are structurally characterized. These orders are called saturated. Finally, the way to apply these results to knowledge spaces are outlined.     

Development of a device to measure human sound localization

Measurements of human sound discrimination and localization are important for basic empirical and clinical applications. After a short survey of other methods such as evoked potentials, the development of a new device to measure human sound localization is described and its use illustrated with some examples. Built from a polyacrylic hemisphere or--in a later version--from an orbicular aluminum frame, the apparatus uses multiple speakers to emit auditory stimuli. The patient sits in the middle of the perimeter and has to press a button when a sound is perceived. In addition, the participant has to identify the correct speaker as the source of the sound. With this method it is possible to map the auditory field.     

Asymmetrical scepticism towards criminal evidence: The role of goal‐ and belief‐consistency

Previous demonstrations of asymmetrical scepticism (i.e., that investigators perceive evidence inconsistent [vs. consistent] with the focal hypothesis of a case as less reliable) have failed to account for the underlying mechanism. This study examined whether inconsistent evidence is discredited due to its inconsistency with a prior belief or because it conflicts with the goal to reach closure in a case. Police trainees (N = 107) were presented with a homicide case and judged the reliability of incriminating or exonerating evidence while entertaining a ‘guilty’ or ‘innocent’ hypothesis concerning a suspect. Asymmetrical scepticism was observed in the guilty condition, but not in the innocent condition, partially supporting the goal‐consistency explanation. Implications for the organization of criminal investigations are discussed. Copyright © 2010 John Wiley & Sons, Ltd.     

The delay of gratification test for adults: Validating a behavioral measure of self-motivation in a sample of older people

Most previous delay of gratification tests were developed for children and are inappropriate for application in adults. The authors therefore developed the Delay of Gratification Test for Adults (DoG-A), which includes four types of reward that are meaningful to adults, namely snacks, real money, hypothetical money, and magazines. Four subscores and two composite scores can be calculated. This study is the first to evaluate the DoG-A and to investigate its association with external variables. A community sample of 147 cognitively healthy participants aged between 60 and 94 years completed a questionnaire and cognitive tests measuring delay discounting, self-regulation, motivational self-concept, personality, wellbeing, and cognitive function. The intercorrelations of the subscales were low to medium and the internal consistency of the composite scores was moderate (?? = .4), indicating relative domain independence of the four reward types. The nomological net established by investigating the relations of the DoG-A with other constructs proved to be fairly meaningful. The correlations of all subscales with the delay discounting rate were significant and moderate. The Snacks subscale showed the most consistent pattern of results in terms of moderate positive correlations with self-reported motivation regulation, optimism, dutifulness, and deliberation. The Snacks subscale also correlated with various measures of wellbeing. A regression analysis showed that DoG Snacks remained a significant predictor of wellbeing when self-reported self-regulation and other variables were controlled. These findings indicate that the DoG-A yields an interpretable behavioral measure of self-motivation and offers a developmentally adequate extension of the delay of gratification paradigm for use with adults.     

A Proof-theoretic View of Necessity

We give a reading of binary necessity statements of the form “ϕ is necessary for ψ” in terms of proofs. This reading is based on the idea of interpreting such statements as “Every proof of ψ uses ϕ”.