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Etude psychophysique et modélisation des traitements de bas niveau sous-tendant la vision des contours des objets

Abstract : The mechanisms of contour formation are known to have different functional properties. A study of the integration of space information between coaxial elements of lines was carried out. Two regimes are present, differentiated from a space separation of approximately a quarter of degree of visual angle : short- and long-range distance regimes. The first one was intensively studied, contrary to the second one. By using an experimental approach and by modeling, the functional characteristics of the long-range regime were measured and partly explained by the primary visual cortex of the Man. The experiments made it possible to obtain some psychophysical characteristics. With stimuli of positive polarities, the short-range regime goes from zero to one third of degree, and is sensitive to the intensity of the inducer (Experiment 1). The long-range regime goes from one third of degree to 2,5 degrees, and is not sensitive to the intensity of the inducer (Experiment 1). The long-range regime seems to be in a general way facilitatory for detection of the target (Experiment 2 and 5), whatever the polarity and the intensity of the inducer. On the other hand, differences between opposite and identical polarities of the stimuli are present for this regime. The interaction OFF-to-ON is in a general way much less facilitatory than the other interactions (Experiment 2 and 5).The luminance of the background field on which the stimuli are presented seemed to interfere in the interactions (Experiment 2), but the control study on naive subjects did not show an effect of this parameter (Experiment 5). According to the space separation between the two stimuli, it is possible to obtain an interaction between the two regimes if the inductive stimulus is placed so that the two regimes compete for the detection of the target (Experiment 3). For positive polarities of the stimuli, the long-range regime proved to have a visual plasticity specific to the direction of alignment of the stimuli (Experiment 4): the vertical direction shows an increase in the detection thresholds of the subjects at the beginning of the experiments, and the horizontal direction a reduction in the detection thresholds of the subjects at the beginning of the experiments. Thereafter, we tried to model these experimental results with the LAMINART model. It simulates a part of the functional properties of the neurons of the primary visual cortex (V1). It reproduces, in a global way, the effects due to the polarities, but does not seem to be sensitive to the factor "space separation". The results of this thesis support the idea that the two regimes of integration of the space information of Iso-orientation are mainly influenced by the primary visual cortex of the Man.
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Submitted on : Thursday, January 15, 2004 - 11:52:26 AM
Last modification on : Thursday, April 23, 2020 - 2:26:28 PM
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Tzvetomir Tzvetanov. Etude psychophysique et modélisation des traitements de bas niveau sous-tendant la vision des contours des objets. Neurosciences [q-bio.NC]. Université Louis Pasteur - Strasbourg I, 2003. Français. ⟨tel-00004179⟩

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