title: Human Brain Reacts to Transcranial Extraocular Light.
abstract: Transcranial extraocular light affects the brains of birds and modulates their seasonal changes in physiology and behavior. However, whether the human brain is sensitive to extraocular light is unknown. To test whether extraocular light has any effect on human brain functioning, we measured brain electrophysiology of 18 young healthy subjects using event-related potentials while they performed a visual attention task embedded with emotional distractors. Extraocular light delivered via ear canals abolished normal emotional modulation of attention related brain responses. With no extraocular light delivered, emotional distractors reduced centro-parietal P300 amplitude compared to neutral distractors. This phenomenon disappeared with extraocular light delivery. Extraocular light delivered through the ear canals was shown to penetrate at the base of the scull of a cadaver. Thus, we have shown that extraocular light impacts human brain functioning calling for further research on the mechanisms of action of light on the human brain.
authors.affiliation: Behavioral Neurology Research Unit, Tampere University Hospital, Tampere, Finland.
authors.forename: Lihua
authors.initials: L
authors.lastname: Sun
authors.affiliation: Behavioral Neurology Research Unit, Tampere University Hospital, Tampere, Finland.
authors.forename: Jari
authors.initials: J
authors.lastname: Peräkylä
authors.affiliation: Behavioral Neurology Research Unit, Tampere University Hospital, Tampere, Finland.
authors.forename: Anselmi
authors.initials: A
authors.lastname: Kovalainen
authors.affiliation: John Magaddino Neuroscience Laboratory, Saint Mary's College of California, Moraga, California, United States of America.
authors.forename: Keith H
authors.initials: KH
authors.lastname: Ogawa
authors.affiliation: Department of Forensic Medicine, School of Medicine, Tampere University, Tampere University Hospital and Fimlab Laboratories, Tampere, Finland.
authors.forename: Pekka J
authors.initials: PJ
authors.lastname: Karhunen
authors.affiliation: Behavioral Neurology Research Unit, Tampere University Hospital, Tampere, Finland.|Department of Neuroscience and Rehabilitation, Tampere University Hospital, Tampere, Finland.
authors.forename: Kaisa M
authors.initials: KM
authors.lastname: Hartikainen
mesh_terms: D000328:Adult; D001288:Attention / Q000502:physiology; D001921:Brain / Q000502:physiology*; D004424:Ear Canal / Q000502:physiology; D004569:Electroencephalography; D005071:Evoked Potentials; D005260:Female; D006801:Humans; D008027:Light; D008297:Male; D033281:Nontherapeutic Human Experimentation; D013702:Temporal Lobe