Human Brain Reacts to Transcranial Extraocular Light

Area of Science:

• Neuroscience
• Sensory Perception
• Chronobiology

Background:

• Birds' brains are affected by transcranial extraocular light, influencing seasonal physiology and behavior.
• The sensitivity of the human brain to extraocular light remains largely unexplored.

Purpose of the Study:

• To investigate the effect of extraocular light on human brain functioning.
• To determine if light delivered via the ear canals can modulate cognitive and emotional processing.

Main Methods:

• Electrophysiology using event-related potentials (ERPs) was measured in 18 healthy young adults.
• Participants performed a visual attention task with emotional and neutral distractors.
• Extraocular light was delivered through the ear canals in experimental conditions.

Main Results:

• Extraocular light delivery abolished the typical emotional modulation of attention-related brain responses.
• Without extraocular light, emotional distractors significantly reduced centro-parietal P300 amplitude compared to neutral distractors.
• Light penetration to the base of the skull via ear canals was confirmed in a cadaver study.

Conclusions:

• Extraocular light significantly impacts human brain functioning, specifically attention and emotional processing.
• The ear canals may serve as a pathway for light to influence the human brain.
• Further research is warranted to elucidate the mechanisms underlying extraocular light's effects on the brain.