RESUMEN
The aim of this experiment was to test the influence of target context on adaptation to scale perturbations introduced by a video display. Participants performed pointing movements without direct vision of their moving hand, although they could see their movements on a video display. Their perceived movements could be reduced, enlarged. or displayed at their actual size. Three target contexts were compared: dark surround, illuminated frame, and familiar object. Movements were executed with or without vision of hand displacement. Results showed that target context enhanced an allocentric coding of the movement, which improved movement execution. However, the effect of target context changed whether or not the displacement of the hand was available. Overall, the results suggest that target context allowed the extraction of dynamic information about movements, which is used to program and control movements. This suggests that target context could be used efficiently to improve spatial accuracy and speed in teleoperation learning. Potential applications include the reduction of difficulties encountered during teleoperation learning through the introduction of visual context.
Asunto(s)
Terminales de Computador , Cinestesia , Percepción de Movimiento , Orientación , Desempeño Psicomotor , Adolescente , Adulto , Femenino , Humanos , Masculino , Propiocepción , Psicofísica , Privación SensorialRESUMEN
This study concerns the adaptation of motor system when the production of movement was visually controlled through a video display. The subjects had to perform a pointing movement in two visual-feedback conditions: they could see the displacement of their hand or only the final location of the hand on the videoscreen. By changing the zoom of the camera, the amplitude of the movement perceived on the screen was increased, decreased or held equal to the actual movement. Results showed that the movement adapted quickly to the apparent distance changes. In the full visual-feedback condition, the adaptation was smaller in magnitude than in the partial visual-feedback condition. Even though the actual movement was always the same, the subjects thought they carried out different movements. Therefore, the subjects did not use kinematic information provided by the kinaesthetic system but essentially visual information furnished by the video-screen. Taken together, these results show that adaptation to scale changes does not allow the achievement of the perception of a single working space but seems rather specific to each scale.
Asunto(s)
Adaptación Fisiológica , Terminales de Computador , Movimiento , Visión Ocular/fisiología , Adulto , Retroalimentación , Femenino , Humanos , Entrevistas como Asunto , Masculino , Persona de Mediana Edad , PercepciónRESUMEN
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.
Asunto(s)
Mal de Altura/fisiopatología , Atención/fisiología , Hipoxia/fisiopatología , Procesos Mentales/fisiología , Respiración con Presión Positiva , Adulto , Mal de Altura/complicaciones , Humanos , Hipoxia/complicaciones , Masculino , Sensibilidad y EspecificidadRESUMEN
BACKGROUND: Exposure to high altitudes requires acclimation or acclimatization, to prevent the negative effects of severe hypoxia. Among several methods, short acclimation with intermittent exposure to severe hypoxia in a hypobaric chamber triggers efficient physiological pre-adaptation mechanisms (11-13). However, we have little knowledge about the cognitive repercussions of such an acclimation protocol. METHODS: Four mountaineers were tested daily in the course of a short acclimation protocol (5 d). After their SaO2 (arterial oxyhemoglogin saturation) were recorded, they carried out a choice reaction time task (Manikin test) twice every day; first at ground level (250 m, control sessions), second at the highest altitude of the day (D1 = 5000 m, D2 = 5500 m, D3 = 6000 m, D4 = 6500 m, D5 = 7000 m). RESULTS: High altitude SaO2 level decreased during the first 3 d, then stabilized around 72-73%. Despite a slight and transient increase at the highest altitude relative to the ground level in D4, the error rate remained low throughout the protocol. Further, response time to the Manikin task did not show significant changes among the days during the acute stage of hypoxia relative to ground level up to 7000 m. CONCLUSIONS: On the whole, it seems that a short acclimation protocol based on intermittent exposure to simulated high altitudes triggered adaptive processes without major impairment in a choice reaction time task during the acute stages of severe hypoxia.