Sharing | EEG in Indoor Lighting Environments

With the advancement of science, technology and living standards, there is an increasing demand for high quality indoor environments in buildings. Given that visual information accounts for more than 90% of daily external information intake, lighting plays a crucial role as a key component of visual information. Prolonged exposure to substandard lighting conditions can lead to visual fatigue, headaches, lack of concentration, increased rate of operational errors, and so on. Current research focuses on lighting parameters, including spectrum, illuminance, relevant color temperature and lighting settings, and the standards for these parameters only provide basic values to meet the needs of the activity without sufficient consideration of the comfort and health needs of the user, which may be related to the failure of the lighting assessment to effectively reflect the impact of the indoor light environment on the individual's psychological response. Lighting environment evaluations mainly include subjective questionnaires, interviews and behavioral tests. However, most of these data suffer from problems such as time lag. Advances in physiological measurement techniques have enabled the collection of immediate data on how the light environment affects individual psychophysiological responses.

Light is converted into electrical signals by photoreceptors in the retina, which are then transmitted through optic nerve fibers to the brain and ultimately to the cerebral cortex. However, EEG technology can record electrophysiological activity in the cerebral cortex. This paper provides an overview of the use of EEG technology in indoor lighting environments over the past 20 years and aims to highlight the progress made in the field, as well as future directions for research and applications in the field.

When stimulated by the light environment, ion channels (Na+ and K+) on cell membranes become active. Neurons strive to achieve a dynamic equilibrium between the resting state when they are at rest and the excited state, resulting in rhythmic fluctuations of neuronal populations in the brain, and these rhythmic fluctuations provide an objective and effective method for studying the light environment. EEG signals are acquired by placing electrodes on the subject's scalp according to the International 10-20 system. More electrodes can be selected to improve the accuracy of the data, but some studies have selected only some of the electrodes to improve the comfort of the subjects and the efficiency of the experiment. In conclusion, in principle the electrodes should be evenly distributed on the scalp.

EEG signals are acquired as waveforms of amplified potentials, and different event-related potentials (ERPs) are distinguished on the basis of the shape and temporal characteristics of the waveforms, and the amplitude and latency of specific ERPs can be used in the analysis of light environment studies. Amplitude correlates with the strength of the brain response triggered by the light stimulus, while latency correlates with the speed of the brain's processing of the light stimulus. Studies have shown that the interaction of external stimuli with the brain's nervous system in a time series can be obtained from EEG. Thus, EEG can provide insights into how the illumination environment affects an individual's psychological , physiological responses and behavioral changes.

The chapter focuses on summarizing and synthesizing the role of EEG in assessing indoor light environments, and its highlights the validity of EEG in assessing indoor light environment conditions, particularly with regard to how spectrum, illuminance, color temperature, and lighting patterns affect brain activity.

For light environment research, there are three main subcategories, one of which focuses on the effects of indoor light environments on alertness. Alertness is the nervous system's response to changes in the external environment and is closely related to neural activity and chemical release in the brain. The second focuses on the use of EEG to assess the effects of indoor lighting on the performance of cognitive activities. When the brain receives stimuli from the light environment, the brain sends out commands, and during cognitive processes the brain reallocates attentional resources, thus affecting cognitive performance. The third is based on the strong correlation between EEG signals and subjective perception to study the effect of indoor lighting environment on comfort.

Although many theoretical studies have revealed the effects of EEG signals on individuals in indoor light environments, there have been few real-world applications. Studies have shown that there are individual differences in how light environments affect comfort and behavior. In order to improve comfort and energy efficiency, it is necessary to build personalized indoor light loop control systems in the future.