Summary
This blinded EEG study in 18 healthy subjects found that light delivered to the ear canal (extraocular/transcranial light) altered brain electrical activity, specifically modifying how emotional stimuli modulated attentional P300 responses in centroparietal regions. While the mechanism remains unknown, the findings suggest non-visual photoreceptive proteins (opsins) in brain tissue may mediate direct light effects on human cognition and emotion, with potential future implications for non-invasive light-based therapies.
Key Findings
- Significant interaction (repeated-measures ANOVA) between emotional stimulus type (neutral vs. threatening) and extraocular light condition (on vs. off) on P300 amplitude in centroparietal brain regions
- Without extraocular light, threatening stimuli reduced P300 amplitude compared to neutral stimuli; with extraocular light applied to the ear canal, this emotional modulation of P300 was abolished
- Cadaver experiment confirmed that light delivered to the ear canal penetrates the base of the skull, supporting the plausibility of transcranial light reaching brain tissue
- Study involved n=18 healthy subjects in a blinded crossover design
Categories
The Science of Light: Investigates extraocular (transcranial) light pathways and their effects on brain electrical activity, with discussion of non-visual opsins as potential mechanisms.
Mood & Mental Wellness: Extraocular light modulated the emotional processing of attentional brain responses (P300 amplitude), suggesting potential implications for emotional regulation.
Author(s)
A Kovalainen
Publication Year
2018
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