Abstract
Exposure to artificial coloured light is unavoidable in our modern life, but we are only just beginning to understand the impact of coloured light on human physiology. The aim of the present study was to determine effects of coloured light exposure on human systemic and brain physiology using systemic physiology augmented functional near-infrared spectroscopy (SPA-fNIRS). We measured changes in haemoglobin concentrations and tissue oxygen saturation in the left and right prefrontal cortices (L-PFC, R-PFC) by fNIRS, and also recorded skin conductance (SC), partial pressure of end-tidal CO2 (PETCO2), and heart-rate variability variables. 17 healthy adults (median age: 29 years, range: 25–65 years, 6 women) were exposed to blue, red, green, or yellow light for 10 minutes. Pre-light and post-light conditions were in darkness. In the L-PFC the yellow evoked a brain activation. SC and PETCO2 did not change during any of the coloured light exposures, but SC increased and PETCO2 decreased for all colours (except green) in the post-light period. Changes in L-PFC haemoglobin concentration were also observed during the post-light period but have to be interpreted with care, because heart rate and SC increased while PETCO2 decreased. The detected effects are potentially of high relevance for choosing room lighting and may possibly be applied therapeutically.
Highlights
We are increasingly exposed to various sources of coloured light, such as advertisements and different kinds of video screens
We selected neuronal physiology by means of functional near-infrared spectroscopy (fNIRS), as well as systemic physiology, represented by skin conductance, end tidal CO2, pressure of end-tidal CO2 (PETCO2), which correlates with PaCO247, several variables of the heart-rate variability (HRV), and the heart rate (HR)
Skin conductance increased for all colour conditions, during green light exposure the increase was less pronounced and not significant after false discovery rate (FDR) correction[48]
Summary
We are increasingly exposed to various sources of coloured light, such as advertisements and different kinds of video screens. The aim of this study was to assess possibly unknown effects of coloured light exposure on adult human subjects’ neuronal and systemic physiology. We selected neuronal physiology by means of fNIRS, as well as systemic physiology, represented by skin conductance, end tidal CO2, PETCO2, which correlates with PaCO247, several variables of the HRV, and the HR. This is the first study employing systemic physiology augmented functional near-infrared spectroscopy (SPA-fNIRS) to assess the effect of coloured light exposure on human physiology. We hypothesized that the different colours blue, green, red, and yellow would affect the outcome variables differently
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