Daily rhythm of vigilance assessed by temporal resolution of the visual system

To assess the daily distribution of temporal resolution in visual detection , binocular double-pulse resolution (DPR) was measured over a 24 h period i n six healthy subjects. DPR showed a significant daily variation with an am plitude for the foveal stimulus of up to 60%. Like in other vigilance-depen dent daily rhythms, optimal performance occurred around midday. The DPR mea surements described here are an excellent method for assessment of vigilanc e and mental alertness (e.g. in pharmacological studies). They show strong time-of-day differences, are highly reliable across successive measurements , and can be fully automated. (C) 2000 Elsevier Science Ltd. All rights res erved.