Spreading and synchronization of intrinsic signals in visual cortex of macaque monkey evoked by a localized visual stimulus

Spatio-temporal maps of the occipital cortex of macaque monkeys were analyzed using optical imaging of intrinsic signals. The images obtained during localized visual stimulation (IS) were compared with the images obtained on presentation of a blank screen (IB). We first investigated spontaneous variations of the intrinsic signals by analyzing the 100 IBs for each of the three cortical areas. Slow periodical activation was observed in alternation over the cortical areas. Cross-correlation analysis indicated that synchronization of spontaneous activation only took place within each cortical area, but not between them. When a small, drifting grating (2degreesX2degrees) was presented on the fovea. a dark spot appeared in the optical image at the cortical representation of this retinal location. It spread bilaterally along the border between V1 and V2, continuing as a number of parallel dark bands covering a large area of the lateral surface of V1. Cross-correlation analysis showed that during visual stimulation the intrinsic signals over all of the three cortical areas were synchronized, with in-phase activation of V1 and V2 and anti-phase activation of V4 and V1/V2. The significance of these extensive synergistic and antagonistic interactions between different cortical areas is discussed. (C) 2003 Elsevier B.V. All rights reserved.

Topographic plasticity in primary visual cortex is mediated by local corticocortical connections

The placement of monocular laser lesions in the adult cat retina produces a lesion projection zone (LPZ) in primary visual cortex (V1) in which the majority of neurons have a normally located receptive field (RF) for stimulation of the intact eye and an ectopically located RF ( displaced to intact retina at the edge of the lesion) for stimulation of the lesioned eye. Animals that had such lesions for 14 - 85 d were studied under halothane and nitrous oxide anesthesia with conventional neurophysiological recording techniques and stimulation of moving light bars. Previous work suggested that a candidate source of input, which could account for the development of the ectopic RFs, was long-range horizontal connections within V1. The critical contribution of such input was examined by placing a pipette containing the neurotoxin kainic acid at a site in the normal V1 visual representation that overlapped with the ectopic RF recorded at a site within the LPZ. Continuation of well defined responses to stimulation of the intact eye served as a control against direct effects of the kainic acid at the LPZ recording site. In six of seven cases examined, kainic acid deactivation of neurons at the injection site blocked responsiveness to lesioned-eye stimulation at the ectopic RF for the LPZ recording site. We therefore conclude that long-range horizontal projections contribute to the dominant input underlying the capacity for retinal lesion-induced plasticity in V1.

Auditory-visual speech integration by prelinguistic infants: Perception of an emergent consonant in the McGurk effect

The McGurk effect, in which auditory [ba] dubbed onto [go] lip movements is perceived as da or tha, was employed in a real-time task to investigate auditory-visual speech perception in prelingual infants. Experiments 1A and 1B established the validity of real-time dubbing for producing the effect. In Experiment 2, 4(1)/(2)-month-olds were tested in a habituation-test paradigm, in which 2 an auditory-visual stimulus was presented contingent upon visual fixation of a live face. The experimental group was habituated to a McGurk stimulus (auditory [ba] visual [ga]), and the control group to matching auditory-visual [ba]. Each group was then presented with three auditory-only test trials, [ba], [da], and [deltaa] (as in then). Visual-fixation durations in test trials showed that the experimental group treated the emergent percept in the McGurk effect, [da] or [deltaa], as familiar (even though they had not heard these sounds previously) and [ba] as novel. For control group infants [da] and [deltaa] were no more familiar than [ba]. These results are consistent with infants'perception of the McGurk effect, and support the conclusion that prelinguistic infants integrate auditory and visual speech information. (C) 2004 Wiley Periodicals, Inc.

Application of X-ray microtomography to numerical simulations of agglomerate breakage by distinct element method

Computer-aided tomography has been used for many years to provide significant information about the internal properties of an object, particularly in the medical fraternity. By reconstructing one-dimensional (ID) X-ray images, 2D cross-sections and 3D renders can provide a wealth of information about an object's internal structure. An extension of the methodology is reported here to enable the characterization of a model agglomerate structure. It is demonstrated that methods based on X-ray microtomography offer considerable potential in the validation and utilization of distinct element method simulations also examined.

Hybrid knowledge representation in a blackboard KBS for liquid retaining structure design

This paper highlights the importance of design expertise, for designing liquid retaining structures, including subjective judgments and professional experience. Design of liquid retaining structures has special features different from the others. Being more vulnerable to corrosion problem, they have stringent requirements against serviceability limit state of crack. It is the premise of the study to transferring expert knowledge in a computerized blackboard system. Hybrid knowledge representation schemes, including production rules, object-oriented programming, and procedural methods, are employed to express engineering heuristics and standard design knowledge during the development of the knowledge-based system (KBS) for design of liquid retaining structures. This approach renders it possible to take advantages of the characteristics of each method. The system can provide the user with advice on preliminary design, loading specification, optimized configuration selection and detailed design analysis of liquid retaining structure. It would be beneficial to the field of retaining structure design by focusing on the acquisition and organization of expert knowledge through the development of recent artificial intelligence technology. (C) 2003 Elsevier Ltd. All rights reserved.

The representation of majorities and minorities in the British press: A content analytic approach

A content analysis examined the way majorities and minorities are represented in the British press. An analysis of the headlines of five British newspapers, over a period of five years, revealed that the words 'majority' and 'minority' appeared 658 times. Majority headlines were most frequent (66%), more likely to emphasize the numerical size of the majority, to link majority status with political groups, to be described with positive evaluations, and to cover political issues. By contrast, minority headlines were less frequent (34%), more likely to link minority status with ethnic groups and to other social issues, and less likely to be described with positive evaluations. The implications of examining how real-life majorities and minorities are represented for our understanding of experimental research are discussed. Copyright (C) 2004 John Wiley Sons, Ltd.

Disrupted cortical proprioceptive representation evokes symptoms of peculiarity, foreignness and swelling, but not pain

Objectives. It has been proposed that disruption of the internal proprioceptive representation, via incongruent sensory input, may underpin pathological pain states, but experimental evidence relies on conflicting visual input, which is not clinically relevant. We aimed to determine the symptomatic effect of incongruent proprioceptive input, imparted by vibration of the wrist tendons, which evokes the illusion of perpetual wrist flexion and disrupts cortical proprioceptive representation. Methods. Twenty-nine healthy and naive volunteers reported symptoms during five conditions: control, active and passive wrist flexion, extensor carpi radialis tendon vibration to evoke illusion of perpetual wrist flexion, and ulnar styloid (sham) vibration. No advice was given about possible illusions. Results. Twenty-one subjects reported the illusion of perpetual wrist flexion during tendon vibration. There was no effect of condition or of whether or not subjects reported an illusion on discomfort/pain (P > 0.28). Peculiarity, swelling and foreignness were greater during tendon vibration than during the other conditions, and greater during tendon vibration in those who reported an illusion of wrist flexion than in those who did not (P < 0.05 for all). Symptoms were reported by at least two subjects in each condition and four subjects reported systemic symptoms (e.g. nausea). Conclusions. In healthy volunteers, incongruent proprioceptive input does not cause discomfort or pain but does evoke feelings of peculiarity, swelling and foreignness in the limb.

Effectiveness of document representation for classification

Conventionally, document classification researches focus on improving the learning capabilities of classifiers. Nevertheless, according to our observation, the effectiveness of classification is limited by the suitability of document representation. Intuitively, the more features that are used in representation, the more comprehensive that documents are represented. However, if a representation contains too many irrelevant features, the classifier would suffer from not only the curse of high dimensionality, but also overfitting. To address this problem of suitableness of document representations, we present a classifier-independent approach to measure the effectiveness of document representations. Our approach utilises a labelled document corpus to estimate the distribution of documents in the feature space. By looking through documents in this way, we can clearly identify the contributions made by different features toward the document classification. Some experiments have been performed to show how the effectiveness is evaluated. Our approach can be used as a tool to assist feature selection, dimensionality reduction and document classification.

Levinasian ethics and the representation of the other in international and cross-cultural management

In this paper, we seek to further the discussion, problematization and critique of west/east identity relations in ICM studies by considering the ethics of the relationship – an issue never far beneath the surface in discussions of Orientalism. In particular we seek to both examine and question the ethics of representation in relation to a critique of what has come to be known as international and cross-cultural management (ICM). To pursue such a discussion, we draw specifically on the ethical elaborations of Emmanuel Levinas as well as his chief interlocutors Jacques Derrida and Zygmunt Bauman. The value of this discussion, we propose, is that Levinas offers a philosophy that holds as its central concept the relationship between the self and Other as the primary ethical and pre-ontological relation. Levinas’ philosophy provides a means of extending the post-colonial critique of ICM, and ICM provides a context in which the Levinasian ethics can be brought to bear on a significant issue on contemporary business and management.

3D protein structure matching by patch signatures

For determining functionality dependencies between two proteins, both represented as 3D structures, it is an essential condition that they have one or more matching structural regions called patches. As 3D structures for proteins are large, complex and constantly evolving, it is computationally expensive and very time-consuming to identify possible locations and sizes of patches for a given protein against a large protein database. In this paper, we address a vector space based representation for protein structures, where a patch is formed by the vectors within the region. Based on our previews work, a compact representation of the patch named patch signature is applied here. A similarity measure of two patches is then derived based on their signatures. To achieve fast patch matching in large protein databases, a match-and-expand strategy is proposed. Given a query patch, a set of small k-sized matching patches, called candidate patches, is generated in match stage. The candidate patches are further filtered by enlarging k in expand stage. Our extensive experimental results demonstrate encouraging performances with respect to this biologically critical but previously computationally prohibitive problem.