Effects of Temporal Light Modulation on Cognitive Performance,Eye Movements, and Brain Function

ABSTRACT

Temporal light modulation (TLM) describes variations in light output from a light source or lighting system and can be a characteristic of their normal operation. TLM at 100 or 120 Hz can disrupt eye movements and reduce visual performance compared to 40 kHz, but little is known of the effects between those frequencies. Such evidence could provide the basis for lighting product and application standards to support the development of energy-efficient lighting systems. This repeated-measures experiment compared the effects of three stimuli (no TLM [DC], 100 Hz, and 500 Hz [both rectangular-wave, 100% modulation depth, 50% duty cycle]) on state anxiety, eye movements (blinks, saccades, fixations, and pupil size), cognitive performance (Stroop task and sentence reading speed), and visual event-related potentials (ERPs). Post-processing of EEG data included dipole source analysis and estimates of source dipole strength. TLM at 100 Hz was associated with larger pupil sizes and greater ERP dipole strength during 100 Hz exposure than no TLM, particularly in the right hemisphere. Cognitive interference was lower for 500 Hz TLM than 100 Hz. State anxiety was unaffected. The addition of TLM to the light source signal increased arousal and altered brain activity; at the highest frequency tested here this reduced cognitive interference. Arousal theory and stochastic facilitation can provide possible explanations.

KEYWORDS:

• Temporal light modulation
• flicker
• brain activity
• cognitive performance
• eye movements

Acknowledgments

Portions of these data formed the M.Sc. thesis of P. Van Roon. The authors thank SR Research (William Schmidt and Marcus Johnson) and Arkalumen, Inc. (Sean Murray) for their in-kind contributions. At NRC, we thank Chantal Arsenault, Sandra Mancini, Ashley Nixon, and Paul Taylor-Sussex for their assistance, and Guy Newsham, Trevor Nightingale, and Alexandra Thompson for their support. At Carleton University, we thank Jila Zakizadeh for assistance.

Disclosure statement

The National Research Council of Canada receives funds from Canadian and foreign government departments and agencies and from private industry that may be affected by the research reported in this paper. Jennifer Veitch serves on committees and boards of the IES, the International Commission on Illumination, and the International Standards Organization, which write recommendations, standards, and guidance related to the topic of this work.

Additional information

Funding

This investigation formed part of National Research Council of Canada projects 44-B3249 (Solid-state lighting for the office of the future) and A1-002833 (Solid-state lighting: Enhancing Energy Efficiency and Ensuring Market Acceptance), and is an output of the NRC High Performance Buildings program. Financial support for this activity was provided by the Clean Energy Fund and EcoEnergy Innovation Initiative (managed by Natural Resources Canada), OSRAM SYLVANIA Inc., the Jim H. McClung Lighting Research Foundation, Natural Resources Canada – Office of Energy Efficiency, the Independent Electricity System Operator Conservation Fund (Province of Ontario), the National Research Council of Canada, and Carleton University.