Time-of-day-dependent Effects of Monochromatic Light Exposure on Human Cognitive Function

Abstract

Light elicits non-visual effects on a wide range of biological functions and behavior. These effects are mediated by a melanopsin-based photoreceptor system that is very sensitive to blue light (440-480 nm) relative to the three-cone visual photopic system. The aim of the current study was to assess the time-of-day-dependent effects of two different wavelength monochromatic lights at 458 nm and 550 nm on human cognitive function. We conducted an experiment in the daytime and nighttime on different days. Twelve subjects were selected, none of whom was either morning-type or eveningtype, as assessed by a translated version of the morningness/ eveningness questionnaire. The cognitive function was measured by event-related potential (ERP) using an oddball task, and arousal level was measured by the Alpha Attenuation Test (AAT). We found that 458 nm light exposure caused a significantly larger P300 amplitude than occurred with 550 nm light. There was a significant interaction among wavelength, time of day, and electrode site. Exposure to 458 nm light induced a larger P300 amplitude at nighttime than in the daytime at the Fz electrode site. The Alpha Attenuation Coefficient (AAC) at nighttime was higher than in the daytime. Our results suggest that short wavelength monochromatic light can affect the circadian rhythms of cognitive functions, and indicate that these effects are mediated by a melanopsin-based photoreceptor system. This study has extended previous findings in terms of time of day, and higher cognitive function by using an endogenous ERP component, P300.

Association between the melanopsin gene polymorphism OPN4*Ile394Thr and sleep/wake timing in Japanese university students

“…Melanopsin, a photopigment contained in a small subset of retinal ganglion cells, plays an important role in non-image forming (NIF) responses, including circadian photoentrainment [1], melatonin suppression [2], pupillary light reflex [3,4], sleep behavior [5,6] and alertness [7,8], by transmitting photic irradiance information to the brain. Parallel studies using genetic ablation of melanopsin ( Opn4 ) in mice [1,9], using a silent-substitution method in humans [4], and using blind subjects [10,11] have demonstrated that the contribution of melanopsin to NIF responses is as important as, or even more important than, that of the classical photoreceptors (rods and cones).…”

Melanopsin, photosensitive ganglion cells, and seasonal affective disorder

“…These data lead to the hypothesis that a melanopsin-mediated effect on alertness may explain the role of melanopsin in SAD (Schmidt et al, 2011). Human studies have found that light causes an acute increase in cognitive performance and alertness (e.g., Badia et al, 1991; French et al, 1990), especially short wavelength light (An et al, 2009; Cajochen et al, 2005; Lockley et al, 2006; Phipps-Nelson et al, 2003; Revell et al, 2010; Zaidi et al, 2007; Figueiro et al, 2007). Based on spectral sensitivity, however, self-reported alertness ratings are driven by a combination of photoreceptors whose contributions may vary across the day (An et al, 2009; Revell et al, 2010).…”

“…Human studies have found that light causes an acute increase in cognitive performance and alertness (e.g., Badia et al, 1991; French et al, 1990), especially short wavelength light (An et al, 2009; Cajochen et al, 2005; Lockley et al, 2006; Phipps-Nelson et al, 2003; Revell et al, 2010; Zaidi et al, 2007; Figueiro et al, 2007). Based on spectral sensitivity, however, self-reported alertness ratings are driven by a combination of photoreceptors whose contributions may vary across the day (An et al, 2009; Revell et al, 2010). Although light may increase alertness by suppressing melatonin when it is released, other as yet unidentified process stimulating the ascending arousal system and cortex are likely during the day when melatonin is low (Lockley and Gooley, 2006).…”

Melanopsin Gene Variations Interact With Season to Predict Sleep Onset and Chronotype

“…Previous research suggests that melanopsin has a role in human circadian entrainment and alertness (An et al, 2009; Cajochen et al, 2005; Lockleyet al, 2003, 2006; Revell et al, 2010; Zaidi et al, 2007). Melanopsin is hypothesized to play a role in circadian influences on alertness, as well as acute, light-induced sleep and alertness responses through three mechanisms: (i) circadian entrainment of sleep propensity, (ii) homeostatic sleep regulation, and (iii) acute effects of light on alertness.…”