DETRIMENTAL INFLUENCE OF BRIGHT LIGHT EXPOSURE ON ALERTNESS, PERFORMANCE, AND MOOD IN THE EARLY-MORNING

The aim of this study was to assess the effects of exposure for one ni ght to moderate bright light (BL) on subjective and objective measures of alertness, performance, and mood. Eight subjects were exposed to e ither BL or dim light (DL) during one night. During the previous day, they were exposed to bright light in both experimental conditions. Noc turnal BL suppressed melatonin secretion and increased body temperatur e. The ability to stay awake during the night, as measured by the powe r density in the alpha band, was significantly improved by BL exposure . BL also improved subjective alertness and performance during the fir st part of the night. However, improvements in the last two variables were followed by marked disruption in early morning patterns, with det erioration of mood and motivation.