To determine whether nonvisual (vestibular and somatosensory) information participates in low-level orientation processing, subjects in different postural conditions (upright, supine, and sitting immobilized) searched for a target distinguishable from distractors by difference in orientation (A. Treisman's, 1985, "pop-out" paradigm). Searches for vertical and horizontal targets were dramatically modified as a function of the postural position, indicating that the processing of orientation in early vision is not only retinal but integrates information from the sensory graviceptors. This visuovestibular phenomenon is interpreted in the conceptual framework of D. H. Foster and P. A. Ward's (1991a) model based on local orthogonal orientation filters and T. A. Stoffregen and G. E. Riccio's (1988) dynamics of balance theory.

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The present study investigates the eects of moda®nil (300 mg/24 h) versus a placebo on the performance of a visual search task during 60 h of sleep deprivation. Moda®nil was administrated in doses of 100 mg three times per day during sleep deprivation. Six healthy volunteers participated in a double-blind experiment including two experimental sessions of 7 days each. The experiment used the visual search paradigm for an`O' target among`Q' distractors and the reverse. The speed and accuracy in detecting the target were measured by RTs slopes (i.e. search rates) and the number of errors (i.e. error rates), respectively. Many authors attribute rapid search rates obtained for Q' targets (low RTs slopes) to parallel/automatic processes and slow search rates obtained for`O' targets (high RTs slope) to serial/attentional processes. The results revealed an asymmetrical search pattern for the detection of`Q' versus`O' targets across the sleep deprivation period (i.e. parallel versus serial search, respectively). Rapid search rates for`Q' targets remained unchanged between placebo and moda®nil conditions during sleep deprivation. However, slow search rates for`O' targets increased linearly in placebo condition, but remained at the same level as the control-test in moda®nil condition. Error rates and search rates also increased. For`O' and`Q' targets, the number of errors increased in the placebo condition, but remained stable in the moda®nil condition. In summary, we can conclude that the administration of moda®nil (300 mg/24 h) during sleep deprivation prevents the slowing of serial processes (attentional shifts) and the increasing of errors. #

This study investigated the effects of hypoxia on parallel/preattentional and serial/attentional processes in early vision, and the use of a positive-end-expiratory-pressure (PEEP) to prevent the impairment in performance. Twenty-one subjects were submitted to an 8-h hypoxia exposure in a hypobaric chamber (4500 m, 589 hPa, 22 degrees C), both with and without a 5-cm H2O PEEP. Subjects carried out a visual search task consisting of detecting a target among distractors in normoxia, in acute and in prolonged hypoxia. Conjointly their sensitivity to acute mountain sickness (AMS) was scored through the Lake Louise AMS scoring system. Results showed that prolonged hypoxia slowed serial/attentional processing whereas parallel/preattentional processes were not impaired either by acute or by prolonged hypoxia. PEEP prevented serial/attentional processes from slowing and those effects were more clearly observed in the AMS sensitive subjects with respect to the AMS insensitive subjects. These results suggest that the slowing induced by prolonged hypoxia is specific to an early visual process that pilots the scanning of an attentional spotlight throughout the visual field.

The present study investigates the eects of moda®nil (300 mg/24 h) versus a placebo on the performance of a visual search task during 60 h of sleep deprivation. Moda®nil was administrated in doses of 100 mg three times per day during sleep deprivation. Six healthy volunteers participated in a double-blind experiment including two experimental sessions of 7 days each. The experiment used the visual search paradigm for an`O' target among`Q' distractors and the reverse. The speed and accuracy in detecting the target were measured by RTs slopes (i.e. search rates) and the number of errors (i.e. error rates), respectively. Many authors attribute rapid search rates obtained for Q' targets (low RTs slopes) to parallel/automatic processes and slow search rates obtained for`O' targets (high RTs slope) to serial/attentional processes. The results revealed an asymmetrical search pattern for the detection of`Q' versus`O' targets across the sleep deprivation period (i.e. parallel versus serial search, respectively). Rapid search rates for`Q' targets remained unchanged between placebo and moda®nil conditions during sleep deprivation. However, slow search rates for`O' targets increased linearly in placebo condition, but remained at the same level as the control-test in moda®nil condition. Error rates and search rates also increased. For`O' and`Q' targets, the number of errors increased in the placebo condition, but remained stable in the moda®nil condition. In summary, we can conclude that the administration of moda®nil (300 mg/24 h) during sleep deprivation prevents the slowing of serial processes (attentional shifts) and the increasing of errors. #