Elucidating effects of short wavelength light on the body using biological signals

This study aimed to clarify the influence on the body caused by the light stimulation of short wavelength light being transmitted to the hypothalamus in the brain through the retinal hypothalamic tract. And the brain waves of the prefrontal cortex reflecting the function of the hypothalamus and melatonin secretion are compared at the time of receiving short wavelength light and at the time of blocking short wavelength light. Short wavelength light refers to light of blue component with a wavelength of 380-495 nm. This component is often contained in the light from the screen of the electronic device and the light of the LED lighting. In recent years, the opportunity for exposure to short wavelength light has increased due to the increase in usage time of electronic devices and the spread of LED lighting. However, it is said that short wavelength light affects the control of the biological rhythm of the day. This is because the absorption band of photoreceptors involved in the biological clock is equal to the wavelength band of short wavelength light. The nighttime light response of this photoreceptor has been confirmed to suppress the secretion of the sleepiness hormone melatonin and the accompanying decrease in sleepiness, but the light response during time zones other than nighttime and the effect on the brain other than sleepiness due to it is unknown. We compared brain wave and the amount of melatonin secretion in the case of receiving light from tablet terminal which contains a lot of short wavelength light components directly and receiving light through glasses which shields short wavelength light. And We elucidated the effects of short wavelength light on the body by detecting differences. As a result of electroencephalogram analysis, it was revealed that the power spectrum of \boldsymbol{\beta} and \boldsymbol{\beta}/\boldsymbol{\alpha} bands in the morning and \boldsymbol{\delta} band in the night decreased by the reception of short wavelength light. In addition, the results of melatonin secretion suggested that the short wavelength light suppressed melatonin production, so that morning light reception reduced stress and night light reception decreased sleepiness.