Effect of intensity of short-wavelength light on electroencephalogram and subjective alertness

Abstract

Short-wavelength light is known to have an effect on human alertness in the night-time. However, there are very few studies that focus on the effect of intensity of light on alertness. This study evaluates the acute alerting ability of short-wavelength light of three different intensities (40 lux, 80 lux and 160 lux). Eight subjects participated in a 60-minute exposure protocol for four evenings, during which electroencephalogram (EEG) as well as subjective sleepiness data were collected. EEG power in the beta range was significantly higher after subjects were exposed to 160 lux light than after they were exposed to 40 lux, 80 lux light or remained in darkness. Also, the alpha theta power was significantly lower under 160 lux light then in darkness. These results show that the effect of intensity on alertness is not linear and further work should be done to investigate the threshold intensity that is required to produce an alerting effect.

Effect of long-wavelength light on electroencephalogram and subjective alertness

“…21,22 These are also indirect evidences that melatonin suppression is not necessary for us to observe an alerting effect of light. Secondly, in previous study, 16 only 160 lx blue light significantly increased alertness. 40 lx and 80 lx blue lights seemed to have an effect, though it is not statistically significant.…”

“…Experiment protocol of this study is kept consistent with the previous study. 16 Each participant completed two sessions over two nights, starting at around the same time (8 p.m.). Participants were fitted with EEG electrodes prior to the start of the exposure.…”

“…Figure 6 shows the results of normalised power for six lighting conditions in three frequency ranges studied (where * indicates statistical significance). Note that the results of dim, 40 lx, 80 lx and 160 lx Blue light from the previous study 16 are added in Figure 6 to give a better comparison. The results showed that EEG beta power is significantly higher after exposure to 160 lx Blue light than remaining in Dim light (p50.05).…”

“…15 In a previous study, we have investigated the alerting effect of short-wavelength light at three light levels (40 lx, 80 lx and 160 lx) in the evening. 16 Results showed that 160 lx light significantly increased alertness, as evaluated by EEG and self-rating questionnaire (Karolinska Sleepiness Scale, KSS). This study aims to expand on the previous work by investigating the impact of long-wavelength on the measures of EEG power and KSS.…”

Aroused and Impulsive Effects of Colour Stimuli on Lateral and Logical Abilities

“…It is suggested that the effective use of colours in the design of classrooms do have significant impacts on students’ perceptual performances. Interestingly, some studies carried out explored the intensity lighting impacts have on people’s electroencephalogram (EEG) power [ 15 , 16 ]. Results have demonstrated the stimulus of short and long wavelength light on people’s alpha, theta, and beta power, suggesting that coloured light can promote acute alertness and improve performance on tasks requiring sustained attention.…”