Testing a dynamic field account of interactions between spatial attention and spatial working memory

Studies examining the relationship between spatial attention and spatial working memory (SWM) have shown that discrimination responses are faster for targets appearing at locations that are being maintained in SWM, and that location memory is impaired when attention is withdrawn during the delay. These observations support the proposal that sustained attention is required for successful retention in SWM: if attention is withdrawn, memory representations are likely to fail, increasing errors. In the present study, this proposal is reexamined in light of a neural process model of SWM. On the basis of the model’s functioning, we propose an alternative explanation for the observed decline in SWM performance when a secondary task is performed during retention: SWM representations drift systematically toward the location of targets appearing during the delay. To test this explanation, participants completed a color-discrimination task during the delay interval of a spatial recall task. In the critical shifting attention condition, the color stimulus could appear either toward or away from the memorized location relative to a midline reference axis. We hypothesized that if shifting attention during the delay leads to the failure of SWM representations, there should be an increase in the variance of recall errors but no change in directional error, regardless of the direction of the shift. Conversely, if shifting attention induces drift of SWM representations—as predicted by the model—there should be systematic changes in the pattern of spatial recall errors depending on the direction of the shift. Results were consistent with the latter possibility—recall errors were biased toward the location of discrimination targets appearing during the delay

A competitive integration model of exogenous and endogenous eye movements

We present a model of the eye movement system in which the programming of an eye movement is the result of the competitive integration of information in the superior colliculi (SC). This brain area receives input from occipital cortex, the frontal eye fields, and the dorsolateral prefrontal cortex, on the basis of which it computes the location of the next saccadic target. Two critical assumptions in the model are that cortical inputs are not only excitatory, but can also inhibit saccades to specific locations, and that the SC continue to influence the trajectory of a saccade while it is being executed. With these assumptions, we account for many neurophysiological and behavioral findings from eye movement research. Interactions within the saccade map are shown to account for effects of distractors on saccadic reaction time (SRT) and saccade trajectory, including the global effect and oculomotor capture. In addition, the model accounts for express saccades, the gap effect, saccadic reaction times for antisaccades, and recorded responses from neurons in the SC and frontal eye fields in these tasks. © The Author(s) 2010

Image Representation in Hypercolumnar Structure by means of Associative Memory

We propose a pattern recognition system based on an architecture close to the one found in human visual cortex which is called Hypercolumns. We use this discrete parametric representation in connection with a sparsley coding associative memory. In principle the application of such a representation appears to be very well suited for data reduction and pattern recognition processes and is part of a neural instruction set [2]. 1 Introduction Besides using properties of single cells and simple neural nets the nervous system exploits structural principles for visual information processing. These principles can be viewed at as having emerged in an optimal way from evolutionary adaption to a certain kind of information processing. The most well known examples of such structural as well as processing principles are layered cell structure, Retinotopic Maps, Feature Maps, Associative Memory or Active Vision. In dealing with these principles we are concerned with a neural instruction set [2] whi..

Flexibility through a Neural Architecture for Visual Orientation in a Natural Environment

We propose a framework to model visual information processing, behavioral control on the base of two-dimensional activity distributions with local interactions. These layers are used to represent parameters of visual data and behavioral variables. Interactions within and among such representations defined as systems of linear or nonlinear differential equations support basic operations of neural information processing. The approach is exemplified through three different models in the domains of visual representation and recognition, saccadic control and navigation in complex environments

Bestandsaufnahmen von Ruestungsaltlastverdachtsstandorten in der Bundesrepublik Deutschland. Bd. 3 Kampfstofflexikon

SIGLEAvailable from TIB Hannover: RN 8422(1996,27),2 / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekBundesministerium fuer Umwelt, Naturschutz und Reaktorsicherheit, Bonn (Germany)DEGerman

Contour Segmentation with Recurrent Neural Networks of Pulse-Coding Neurons

. The performance of technical and biological vision systems crucially relies on powerful processing capabilities. Robust object recognition must be based on representations of segmented object candidates which are kept stable and sparse despite the highly variable nature of the environment. Here, we propose a network of pulse-coding neurons based on biological principles which establishs such representations using contour information. The system solves the task of grouping and figureground segregation by creating flexible temporal correlations among contour extracting units. In contrast to similar previous approaches, we explicitly address the problem of processing grey value images. In our multi-layer architecture, the extracted contour features are edges, line endings and vertices which interact by introducing facilatory and inhibitory couplings among feature extracting neurons. As the result of the network dynamics, individual mutually occluding objects become defined by temporally..

Review of suspected warfare-related environmental damage in the Federal Republic of Germany. Vol. 3 Chemical agents dictionary

The collection of data comprises 53 individual substances as well as 6 isomere mixtures of important chemical agents used or produced in the course of the two world wars. (orig.)SIGLEAvailable from TIB Hannover: RN 8422(1996,32),2 / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekBundesministerium fuer Umwelt, Naturschutz und Reaktorsicherheit, Bonn (Germany)DEGerman

Branchentypische Inventarisierung von Bodenkontaminationen auf Ruestungsaltlastenstandorten. Bd. 2

A summary is given on the German pyrotechnic factories before World War II, on the produced kind, composition and amount by pyrotechnical articles (colored signal items, marker bombs, smoke signals, obscurants, tracers, anti-pathfinders) and on the applied production processes. Corresponding informations together with a discussion of environmental effects and potential contaminated sites are compiled for chemical warfare items (phosgene, lost-mustard gas, chlorinated formates, arsenical compounds) and for the production, storage, dismantlement, recycling and waste disposal of ammunitions and explosives with special regard to army training areas. (WEN)Available from TIB Hannover: RN 8422(1994,43,2) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEBundesministerium fuer Umwelt, Naturschutz und Reaktorsicherheit, Bonn (Germany)DEGerman