Un calcul des propositions pour les systèmes déductifs contradictoires

Sans résumé     

Effect of stimulus intensity on manual and saccadic reaction time

Reaction time (RT) decreases with stimulus intensity. Hughes and Kesley (1984) demonstrated, however, that the effect of stimulus intensity on simple RT is larger for manual than for saccadic responses. We reexamined this relation under various conditions. The dissociation occurred when the task enabled the generation of exogenous saccades. We found, however, no dissociation if endogenous saccades had to be executed. It is hypothesized that the different effects of intensity result from the simplified neuronal processing of exogenous saccades performed in the direct route from the retina to the superior colliculus.     

On the reducibility of questions

The concepta question is reducible to a non-empty set of questions is defined and examined. The basic results are: (1) each question which is sound relative to some of its presuppositions is reducible to some set of binary (i.e. having exactly two direct answers) questions; (b) each question which has a finite number of direct answers is reducible to some finite set of binary questions; (c) if entailment is compact, then each normal question (i.e. sound relative to its presuppositions) is reducible to some finite set of binary questions.     

Activity of common marmosets (Callithrix jacchus) in limited spaces: hand movement characteristics

The increasing popularity of marmoset monkeys (Callithrix jacchus) in anatomical, behavioral, and electrophysiological studies has called for a detailed analysis of their natural behavior within limited spaces. In the present study, the authors analyzed hand movements during horizontal and vertical progressions in a cylinder. The trajectory of each hand covered the entire cylinder floor during horizontal progressions and the entire cylinder wall during vertical progressions. Different marmosets have different patterns of hand movement. The average maximum angle of hand movements for all marmosets during horizontal and vertical progressions oscillates, although the average over time is constant and similar for both hands, whereas head movements during horizontal progressions become smaller with successive progressions. Another observed difference between rats and monkeys was in the size of head and hand movements at the beginning of each experimental session. During the 1st horizontal progression, all marmosets moved their heads to a greater extent than their hands. This sequential head and hand movement is referred as bistable behavior. The bistable pattern of motor behavior, which was also observed in successive progressions, may be derived from an inherent fear of predators or exploratory interest of a novel environment.     

An Abductive Question-Answer System for the Minimal Logic of Formal Inconsistency $$\mathsf {mbC}$$ mbC

Studia Logica - The aim in this paper is to define an Abductive Question-Answer System for the minimal logic of formal inconsistency $$\mathsf {mbC}$$ . As a proof-theoretical basis we employ the...     

Microstructure and superconductivity of bulk BPSCCO/LPMO composite

Bulk superconducting (SC) ceramics containing BPSCCO and LPMO (Lanthanum/Lead – manganite phase) have been produced. The initial components were prepared by a low-temperature Pechini method. The submicron powders in weight ratio 90/10 Bi_1.6Pb_0.4Sr₂Ca₂Cu₃O_z/La_0.6Pb_0.4MnO₃ (nominal composition) were heat treated at 840°C. The duration of the heat treatment effect (60 and 100?h) of the composite on the transformation of the microstructure was studied. The obtained composites were analyzed by scanning electron microscopy (SEM) and by the method of energy-dispersive X-ray spectroscopy (EDX). They contain several phases. It was established that the SC 2212 phase is predominate in the composite. The phase La_0.6Pb_0.4MnO₃ transforms in solid solution with preliminary composition La_0.5(Sr?+?Ca)_0.5Mn_{1? z} Cu _z O₃, which after full replacement of the La and Mn ions leads to the appearance of phases with nominal composition Sr_{1? x} Ca _x CuO _y . AC and DC magnetization measurements were used to study the SC and magnetic properties of the samples. Both samples are SC with critical temperatures 75 and 77?K, respectively. It was concluded that the SC and magnetic phases stably coexist in the composite sintered at 60?h heat treatment at 840°C.     

Increasing stimulus intensity does not affect sensorimotor synchronization

When people synchronize taps with isochronously presented stimuli, taps usually precede the pacing stimuli [negative mean asynchrony (NMA)]. One explanation of NMA [sensory accumulation model (SAM), Aschersleben in Brain Cogn 48:66–79, 2002] is that more time is needed to generate a central code for kinesthetic-tactile information than for auditory or visual stimuli. The SAM predicts that raising the intensity of the pacing stimuli shortens the time for their sensory accumulation, thereby increasing NMA. This prediction was tested by asking participants to synchronize finger force pulses with target isochronous stimuli with various intensities. In addition, participants performed a simple reaction-time task, for comparison. Higher intensity led to shorter reaction times. However, intensity manipulation did not affect NMA in the synchronization task. This finding is not consistent with the predictions based on the SAM. Discrepancies in sensitivity to stimulus intensity between sensorimotor synchronization and reaction-time tasks point to the involvement of different timing mechanisms in these two tasks.     

Logical rules of visual brain: From anatomy through neurophysiology to cognition

Humans can easily recognize objects as complex as faces even if they have not seen them in such conditions or context before. It seems that perceptually we are insensitive to the exact properties of an object’s parts but the same parts in different configurations or contexts may introduce contradictory effects. From a computational point of view, we are often insensitive to changes of some symbols, but the same symbols may lead to different classification of the same object. In present work we are looking for the anatomical and neurophysiological basis of these perceptual effects. We describe interactions between parts and their configurations in different areas of the visual brain on the basis of a single cell electrophysiological activity in the thalamus, and cortical areas V1 and V4. Our model is based on feedforward (FF) and feedback (FB) interactions between these areas. In the retina and thalamus simple light spots are classified, V1 is the first area extracting edge orientation and V4 is the first area sensitive to simple shapes. The FF pathways combine properties extracted in each area into hypothetical objects. Area V1 presents concepts of orientations, while area V4 presents concepts of a simple shape. The FB pathways are responsible for comparison of the learned concepts with extracted object’s properties – they form predictions. In each area structure related predictions are tested against hypothesis. We formulate a theory in which different visual stimuli are described through their condition attributes: responses in LGN, V1, and V4 neurons are divided into several ranges and are treated as decision attributes. Applying rough set theory [Pawlak, Z. (1991). Rough sets – theoretical aspects of reasoning about data. Boston, London, Dordrecht: Kluwer Academic Publishers] we have divided our stimuli into area dependent equivalent classes. We propose that relationships between decision rules in each area are determined by two different logical rules: “driver logical rule” of FF and “modulator logical rule” of FB pathways. These interactions are proposed to be a neurophysiological basis of the object classification.