In this article we report some findings about visual imagery in patients with stable homonymous hemianopia compared to healthy control subjects. These findings were obtained by analyzing the gaze control through recording of eye movements in different phases of viewing and imagery. We used six different visual stimuli for the consecutive viewing and imagery phases. With infrared oculography, we recorded eye movements during this presentation phase and in three subsequent imagery phases in absence of the stimulus. Analyzing the basic parameters of the gaze sequences (known as "scanpaths"), we discovered distinct characteristics of the "viewing scanpaths" and the "imagery scanpaths" in both groups, which suggests a reduced extent of the image within the cognitive representation. We applied different similarity measures (string/vector string editing, Markov analysis). We found a "progressive consistency of imagery," shown through raising similarity values for the comparison of the late imagery scanpaths. This result suggests a strong top-down component in picture exploration: In both groups, healthy subjects and hemianopic patients, a mental model of the viewed picture must evolve very soon and substantially determine the eye movements. As our hemianopic patients showed analogous results to the normal subjects, we conclude that these patients are well adjusted to their deficit and, despite their perceptual defect, have a preserved cognitive representation, which follows the same top-down vision strategies in the process of visual imagery.

E. B. Dynkin undA. A. Juschkewitsch, Sätze und Aufgaben über Markoffsche Prozesse. Übers. a. d. Russ. (Heidelberger Taschenbücher, Band 51). XII + 220 S. m. 56 Abb. Berlin/Heidelberg/New York 1969. Springer-Verlag. Preis brosch. DM 14,80 .

Visual Imagery in Hemianopic Patients

Keywords: zero or one law ; system of non-overlapping circles on the plane Note: Professor Pach's number: [026] Reference DCG-ARTICLE-1984-001 Record created on 2008-11-14, modified on 2017-05-12

/pdf/discrete-convex-functions-and-proof-of-the-six-circle-18xwp5s9hc.pdf

Discrete convex functions and proof of the six circle conjecture of Fejes Toth

Die Monte Carlo Methode wurde zur Losung verschiedener verwickelter Probleme der numerischen Mathematik entwickelt. Sie hat sich in vielfaltigen Anwendungsbereichen als machtvolles Instrument zur Bewaltigung komplexer Berechnungsaufgaben bewahrt. Als Beispiele konnen die Unternehmensforschung [14, 17, 27, 33]1), die Nuklear-Physik [4], die Nachrichten- und Regelungstechnik [16, 24, 29], das Verkehrswesen (vgl. die Beitrage in diesem Band) und viele weitere Bereiche aufgefuhrt werden.

Die Monte Carlo Methode

The stochastic dynamics toward the final attractor in exponential distributed time-delay non-linear models is presented, then the passage time statistic is studied analytically in the small noise approximation. The problem is worked out by going to the associated two-dimensional system. The mean first passage time \(\left\langle t_{e}\right\rangle \) from the unstable state for this non-Markovian type of system has been worked out using two different approaches: firstly, by a rigorous adiabatic Markovian approximation (in the small mean delay-time \(\epsilon =\lambda ^{-1}\)); secondly, by introducing the stochastic path perturbation approach to get a non-adiabatic theory for any \(\lambda \). This first passage time distribution can be written in terms of the important parameters of the models. We have compared both approaches and we have found excellent agreement between them in the adiabatic limit. In addition, using our non-adiabatic approach we predict a crossover and a novel behavior for the relaxation scaling-time as a function of the delay parameter which for \(\lambda \ll 1\) goes as \(\left\langle t_{e}\right\rangle \sim 1/\sqrt{\lambda }\).

Passage Time Statistics in Exponential Distributed Time-Delay Models: Noisy Asymptotic Dynamics

We report on the experimental observation and characterization of the bifurcation diagram, dynamical properties and fluctuations of spatially modulated kinks in a shallow one-dimensional fluidized granular layer subjected to a periodic air flow. We show the appearance of these solutions as the layer undergoes a parametric instability. Due to the inherent fluctuations of the granular layer, the kink profile exhibits an effective wavelength, termed the precursor, which modulates spatially the homogeneous states and drastically modifies the kink dynamics. We characterize the average and fluctuating properties of this solution. The long-term evolution of these kinks is dominated by a hopping dynamics, related directly to the underlying spatial structure and inherent fluctuation. The properties of this motion can be described by a Brownian particle in a symmetric periodic potential. Both the noise intensity of the Brownian fluctuations and the amplitude and periodicity of the potential arise from the underlying precursor structure.

E. B. Dynkin undA. A. Juschkewitsch, Sätze und Aufgaben über Markoffsche Prozesse. Übers. a. d. Russ. (Heidelberger Taschenbücher, Band 51). XII + 220 S. m. 56 Abb. Berlin/Heidelberg/New York 1969. Springer-Verlag. Preis brosch. DM 14,80 .

Citations

Visual Imagery in Hemianopic Patients

Discrete convex functions and proof of the six circle conjecture of Fejes Toth

Die Monte Carlo Methode

Passage Time Statistics in Exponential Distributed Time-Delay Models: Noisy Asymptotic Dynamics

Dynamics of spatially modulated kinks in shallow granular layers

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Sätze und Aufgaben über Markoffsche Prozesse

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