The Puzzling Role Of Biophotons In The Brain - Technology Review: Microtubules are the internal scaffolding inside cells, providing structural support but also creating highways along which molecular machines transport freight around the cell. They're extraordinary things. Could it be that they also work like optical fibres?
Maybe. They go on to suggest that the light channelled by microtubules can help to co-ordinate activities in different parts of the brain. It's certainly true that electrical activity in the brain is synchronised over distances that cannot be easily explained. Electrical signals travel too slowly to do this job, so something else must be at work.