Abstract
Vigilance usually deteriorates over prolonged driving at non-optimal times of day. Exposure to blue-enriched light has shown to enhance arousal, leading to behavioral benefits in some cognitive tasks. However, the cognitive effects of long-wavelength light have been less studied and its effects on driving performance remained to be addressed. We tested the effects of a blue-enriched white light (BWL) and a long-wavelength orange light (OL) vs. a control condition of dim light on subjective, physiological and behavioral measures at 21:45 h. Neurobehavioral tests included the Karolinska Sleepiness Scale and subjective mood scale, recording of distal-proximal temperature gradient (DPG, as index of physiological arousal), accuracy in simulated driving and reaction time in the auditory psychomotor vigilance task. The results showed that BWL decreased the DPG (reflecting enhanced arousal), while it did not improve reaction time or driving performance. Instead, blue light produced larger driving errors than OL, while performance in OL was stable along time on task. These data suggest that physiological arousal induced by light does not necessarily imply cognitive improvement. Indeed, excessive arousal might deteriorate accuracy in complex tasks requiring precision, such as driving.
Highlights
Vigilance, or tonic alertness, is a preparatory state to optimally attend and respond to the environment (Posner and Petersen, 1990; Oken et al, 2006)
There were no differences in the distribution of caffeine intake (χ22 = 0.525; p = 0.77; 50% in blue-enriched white, 38% in orange and 36% in dim light (DL)) or tobacco use (χ22 = 1.85; p = 0.40; 8% in blue-enriched white, 15% in orange and 0% in DL) across groups during the day of the experimental session
Since exposure to light enhances alertness, our study explored the influence of light on prolonged simulated driving at night
Summary
Tonic alertness, is a preparatory state to optimally attend and respond to the environment (Posner and Petersen, 1990; Oken et al, 2006). Vigilance maintenance during driving is highly demanding and frequently results in both mental fatigue and sleepiness. Epidemiological research (Folkard, 1997; Di Milia et al, 2011) confirms that traffic accidents are most frequent at certain times, reaching their maximum around 3–5 a.m. when the levels of body temperature and vigilance are minimal. These results point out the relevance of circadian rhythms on human performance and safety
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