DISENTANGLING DAYLIGHT AND ELECTRIC LIGHTING EFFECTS ON PREFRONTAL ACTIVITY AND AUTONOMIC FUNCTION: METHODOLOGICAL CONSIDERATIONS FOR ECOLOGICALLY VALID NEUROPHYSIOLOGICAL RESEARCH

Research on the non-visual effects of light has demonstrated modulation of cognitive, physiological, and autonomic processes. However, most of the existing evidence originates from laboratory studies relying on simplified and highly controlled stimuli, which substantially differ from the complex and dynamic exposure patterns encountered in everyday environments. Investigating how daylong light exposure influences cognitive function and autonomic response therefore requires experimental paradigms that preserve neurophysiological specificity while accommodating real-world variability.

A multi-day experimental protocol was designed to assess prefrontal cortical activity and autonomic function under daylit and electrically lit office-like environments. Participants were exposed to specific lighting conditions during two consecutive days of continuous exposure for 11 hours. Functional near-infrared spectroscopy was used to quantify prefrontal hemodynamics during scheduled cognitive tasks and resting-state periods embedded within a typical office-work schedule. Lighting conditions enabled controlled investigation of spectral composition, temporal dynamics and spatial light distribution under otherwise comparable exposure conditions.

In parallel, autonomic and physiological biomarkers – including heart rate, heart rate variability, electrodermal activity, and core body temperature – were continuously recorded using wearable sensors over extended periods encompassing baseline, experiment and post-experiment days. This longitudinal monitoring allows characterisation of cognitive and autonomic state and intra-individual variability extending beyond the semi-controlled environment.

This contribution focuses on methodological considerations related to the integration of fNIRS with long-term wearable-based autonomic monitoring in ecologically valid settings, including feasibility, signal stability across days, and challenges associated with multimodal synchronisation and interpretation. The proposed framework supports future investigation of light-brain-body interactions beyond the confines of the laboratory.