Causal ambiguity and partial orders in event structures

Event structure models often have some constraint which ensures that for each\ud system run it is clear what are the causal predecessors of an event (i.e. there is no causal ambiguity). In this contribution we study what happens if we remove\ud such constraints. We define five different partial order semantics that are intentional in the sense that they refer to syntactic aspects of the model. We also define an observational partial order semantics, that derives a partial order from just the event traces. It appears that this corresponds to the so-called early intentional semantics; the other intentional semantics cannot be observationally characterized. We study the equivalences induced by the different partial order definitions, and their interrelations

Competing Sound Sources Reveal Spatial Effects in Cortical Processing

Neurons in the avian auditory forebrain show strong sensitivity to the spatial configuration of two competing sources, even though there is only weak spatial dependence for any single source

Divisive Gain Modulation with Dynamic Stimuli in Integrate-and-Fire Neurons

The modulation of the sensitivity, or gain, of neural responses to input is an important component of neural computation. It has been shown that divisive gain modulation of neural responses can result from a stochastic shunting from balanced (mixed excitation and inhibition) background activity. This gain control scheme was developed and explored with static inputs, where the membrane and spike train statistics were stationary in time. However, input statistics, such as the firing rates of pre-synaptic neurons, are often dynamic, varying on timescales comparable to typical membrane time constants. Using a population density approach for integrate-and-fire neurons with dynamic and temporally rich inputs, we find that the same fluctuation-induced divisive gain modulation is operative for dynamic inputs driving nonequilibrium responses. Moreover, the degree of divisive scaling of the dynamic response is quantitatively the same as the steady-state responses—thus, gain modulation via balanced conductance fluctuations generalizes in a straight-forward way to a dynamic setting

Responses of Tectal Neurons to Contrasting Stimuli: An Electrophysiological Study in the Barn Owl

The saliency of visual objects is based on the center to background contrast. Particularly objects differing in one feature from the background may be perceived as more salient. It is not clear to what extent this so called “pop-out” effect observed in humans and primates governs saliency perception in non-primates as well. In this study we searched for neural-correlates of pop-out perception in neurons located in the optic tectum of the barn owl. We measured the responses of tectal neurons to stimuli appearing within the visual receptive field, embedded in a large array of additional stimuli (the background). Responses were compared between contrasting and uniform conditions. In a contrasting condition the center was different from the background while in the uniform condition it was identical to the background. Most tectal neurons responded better to stimuli in the contrsating condition compared to the uniform condition when the contrast between center and background was the direction of motion but not when it was the orientation of a bar. Tectal neurons also preferred contrasting over uniform stimuli when the center was looming and the background receding but not when the center was receding and the background looming. Therefore, our results do not support the hypothesis that tectal neurons are sensitive to pop-out per-se. The specific sensitivity to the motion contrasting stimulus is consistent with the idea that object motion and not large field motion (e.g., self-induced motion) is coded in the neural responses of tectal neurons

Pewna propozycja uniwersalnego modelu akcji

In the paper a model of action is described that is universal in the sense that it may serve to represent actions of any kind: discrete, continuous, or partially discrete and partially continuous. The model is founded on the assumption that an action is executed in a universe of objects. It describes how the possible executions change the situation of involved objects. It exploits the fact that executions are represented such that fragments of executions are represented such that their closed segments admit only trivial automorphisms. The model has an algebraic strucure and it is a directed complete partial order.Praca zawiera opis pewnego modelu akcji, który jest uniwersalny w tym sensie, że może służyć do reprezentowania akcji dowolnego rodzaju: dyskretnych, ciągłych, lub częściowo dyskretnych i częściowo ciągłych. Model ten opiera się na za lożeniu, że akcja jest wykonywana w pewnym środowisku obiektów. Opisuje jak możliwe wykonania akcji zmieniają sytuacje zaangażowanych obiektów. Wykorzystuje fakt, że fragmenty wykonań akcji są reprezentowane tak, że ich ograniczone segmenty mają jedynie trywialne automorfizmy. Model ma pewną strukturę algebraiczną i częściowy porządek przy którym podzbiory skierowane mają kresy górne

Pewien model akcji i jego własności

In the paper a model of action is described that is universal in the sense that it may serve to represent actions of any kind: discrete, continuous, or partially discrete and partially continuous. The model is founded on the assumption that an action is executed in a universe of objects. It describes how the possible executions change the situation of involved objects. It exploits the fact that executions are represented such that their bounded segments admit only trivial automorphisms. Consequently, the model has an algebraic structure and is a directed complete partial order.Praca zawiera opis pewnego modelu akcji, który jest uniwersalny w tym sensie, że może służyć do reprezentowania akcji dowolnego rodzaju: dyskretnych, ciągłych, lub częściowo dyskretnych i częściowo ciągłych. Model ten opiera się na założeniu, że akcja jest wykonywana w pewnym środowisku obiektów. Opisuje jak możliwe wykonania akcji zmieniają sytuacje zaangażowanych obiektów. Wykorzystuje fakt, że wykonania akcji są reprezentowane tak, że ich ograniczone segmenty mają jedynie trywialne automorfizmy. Dzięki temu model ma pewną strukturę algebraiczną i częściowy porządek przy którym podzbiory skierowane mają kresy górne

On algorithmic simulation

Nie ma dotychczas ostatecznie ukształtowanej teorii symulacji. W pracy w możliwie ścisły sposób temat jest przedstawiony z wykorzystaniem pojęć matematyczych. Podstawowe sa tutaj pojęcia algorytmu i obliczenia.The mathematical formulation of the simulation problem is given

Częściowo uporządkowane dziedziny do reprezentowania działalności

The paper describes structures which can be used to represent activities of broad class. The concept of event structure is generalized to represent activities which may be discrete, continuous, or of mixed nature. Configuration structures of the more general event structures are used to deńe axiomatically configuration domains. Elements of such domains are abstract representants of runs of represented activities. The partial order of elements reects how each run extends to longer runs. It is shown that configuration domains deńe event structures which can be interpreted as interactions of sets of objects.Praca opisuje struktury, których można użyć do reprezentowania szeroko rozumianych działalności. Uogólnia struktury zdarzeń tak, by mogły reprezentować działalności dyskretne, ciągłe i mieszanej natury. Konfiguracje tak uogólnionych struktur zdarzeń zostały użyte do aksjomatycznej definicji dziedzin konfiguracji. Elementy takich dziedzin są abstrakcyjnymi reprezentantami przebiegów reprezentowanych działalności. Pokazano, że dziedziny konfiguracji definiują struktury zdarzeń, które można interpretować jako współdziałania pewnych zbiorów obiektów