Sujet(s)
Sujet âgé/statistiques et données numériques , Conduite automobile/statistiques et données numériques , Accidents de la route/législation et jurisprudence , Accidents de la route/prévention et contrôle , Accidents de la route/statistiques et données numériques , Adaptation psychologique , Répartition par âge , Facteurs âges , Sujet âgé/psychologie , Conduite automobile/législation et jurisprudence , Conduite automobile/psychologie , Europe/épidémiologie , France/épidémiologie , Humains , Changement socialRÉSUMÉ
A circadian rhythm for visual sensitivity has been intensively assessed in animals. This rhythm may be due to the existence of a circadian clock in the mammalian eye, which could account for fluctuating sensitivity to light over the day in certain species. However, very few studies have been devoted to the human visual system. The present experiment was designed to assess a possible rhythm of visual sensitivity using a psychophysical method over the whole 24h period. Twelve subjects underwent visual detection threshold measures in a protocol that allowed one point every 2h. The results show that the visual detection threshold changes over the 24h period, with high thresholds in the morning, a progressive decrease over the day and the early night, and an increase during the last part of the night. These data suggest that a circadian rhythm influences visual sensitivity to mesopic luminance in humans.
Sujet(s)
Rythme circadien/physiologie , Vision/physiologie , Adulte , Femelle , Humains , Mâle , Stimulation lumineuse , Photopériode , PsychophysiqueRÉSUMÉ
The present experiment was designed to assess daily fluctuations of visual discriminability, a function reflecting the resolution power of the visual sensitivity by measure of a differential threshold. Sixteen subjects underwent a visual discrimination threshold task (using the constant method) in a protocol allowing one point every 2h over the 24h period. The results show that the visual discrimination threshold is low in the morning and increases progressively over the day, reaching a first peak at 22:00. During the night, the same pattern occurs, with low threshold levels at the beginning of the night and high levels at the end. This profile is quite different from that of detection threshold variations, suggesting that the two visual functions are under the control of different underlying mechanisms. Two interpretations could account for this discrepancy. The first relates to different oscillators in the eye for detection and discrimination. The second refers to a possible linkage of visual discriminability with the sleep-wake cycle since threshold measures were systematically low (i.e., high resolution power) after long sleep periods.