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Contextual suppression and protection in schizophrenic patients

Résumé

INTRODUCTION: Contextual processing is often strongly deteriorated in schizophrenic patients as found, for example, in higher cognitive as well as lower visual paradigms. In visual detection tasks, impoverished contextual facilitation was attributed to aberrant excitatory neural circuits. On the other hand, we found contextual suppression, possibly related to neural inhibition, to be fast and intact in a visual backward masking task. Here, we combine a suppressive with a "protective" paradigm to further our understanding of the contextual deficiencies of schizophrenic patients in visual information processing. METHODS: Twenty three schizophrenic patients and 18 healthy controls were asked to discriminate the offset direction of a vernier target, which was followed by one of a variety of masks for several stimulus onset asynchronies (SOAs). RESULTS: As in previous studies, patients needed clearly longer SOAs than controls. However, when longer SOAs were taken into account, increases as well as decreases in backward mask strength had comparable effects in patients and controls. CONCLUSIONS: From these results, we suggest that complex spatial processing is fast and intact in schizophrenic patients.

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Concepts associés (32)
Système visuel humain
Le est l'ensemble des organes participant à la perception visuelle humaine, de la rétine au système sensori-moteur. Son rôle est de percevoir et d'interpréter deux images en deux dimensions en une image en trois dimensions. Il est principalement constitué de l'œil (et plus particulièrement la rétine), des nerfs optiques, du chiasma optique, du tractus optique, du corps genouillé latéral, des radiations optiques et du cortex visuel. En première approximation, l'œil peut être assimilé à un appareil photographique.
Visual processing
Visual processing is a term that is used to refer to the brain's ability to use and interpret visual information from the world around us. The process of converting light energy into a meaningful image is a complex process that is facilitated by numerous brain structures and higher level cognitive processes. On an anatomical level, light energy first enters the eye through the cornea, where the light is bent. After passing through the cornea, light passes through the pupil and then lens of the eye, where it is bent to a greater degree and focused upon the retina.
Vue
thumb|250px|Ommatidies de krill antarctique, composant un œil primitif adapté à une vision sous-marine. thumb|250px|Yeux de triops, primitifs et non mobiles. thumb|250px|Yeux multiples d'une araignée sauteuse (famille des Salticidae, composée d'araignées chassant à l'affut, mode de chasse nécessitant une très bonne vision). thumb|250px|Œil de la libellule Platycnemis pennipes, offrant un champ de vision très large, adapté à un comportement de prédation.
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