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.

Background: Intracranial intraparenchymal schwannomas (IS) are rare tumors that have mainly been described in case reports. Here, we report on a case of a brainstem IS and included a comprehensive literature review. Case Description: A 74-year-old man presented with progressive gait disturbances. CT- and MRI-imaging revealed a contrast-enhancing mass accompanied by a cyst in the dorsolateral pons. Hemangioblastoma was suspected and surgery was advised. During surgery, gross total resection of a non-invasive tumor was performed. Postoperative recovery was uneventful. Based on histopathological examination, the intraparenchymal brainstem tumor was diagnosed as schwannoma. Conclusion: Our extensive review illustrates that ISs are benign tumors that most often present in relatively young patients. Malignant cases have been described but form an extremely rare entity. Preoperative diagnosis based on radiological features is difficult but should be considered when peritumoral edema, calcifications, and cysts are noted. In benign cases, gross total resection of the lesion is curative. To adequately select this treatment and adjust the surgical strategy accordingly, it is important to include IS in the preoperative differential diagnosis when the abovementioned radiological features are present.