So I spent today playing with human brains. The first time you hold someone’s loves, hopes and fears between your hands is really quite a numinous moment. It is just amazing to reflect that a person’s entire memory, their desires and hates, their quirks and oddities, are all written as a pattern of neural connections onto that orange-sized chunk of porridgy stuff. It makes me remember why I’m here, that in spite of how heavy and difficult the work load is, I really am in the privileged position of learning how our biology, our brains, our behavior, really works.
Just thought I’d like to share…
Batteries power the clock in your living room. Sunlight powers the one in your brain—or at least keeps it accurate. That jet lag you feel when you step off a plane after an epic trip is caused by a brain clock, or circadian rhythm, out of sync with the world. Therefore, the best thing you can do after such a trip? Is go out into the sunlight, and stay in it long enough for the sun and the brain clock to synchronize.
Sunlight is absorbed by special cells in the eye called intrinsically photosensitive retinal ganglion cells (ipRGCs). These cells do not need the rods and cones in the eye responsible for vision. Instead, they contain the pigment melanopsin that absorbs the sunlight directly. The ipRGCs then project to the superchiasmatic nucleus (SCN), which contains the “clock cells.” Levels of PER and CRY proteins in these cells increase and decrease on a regular time schedule, marking the 24 hours of the day (more or less), and tell the brain what time it is. [If you want more detail on that, let me know. It’s pretty amazing].
At least, that’s the classic model.
But what’s this? New research is saying that we don’t need the ipRGCs for our circadian rhythms either. The rods and cones of the retina can do a fine job setting the brain clock without these special melanopsin-containing cells. Surprisingly, The retina seems to have a rhythm of its own! In fact, if you take a retina, put it in a petri dish, and then sync it to light, you can sync the clock of SCN cells by just plopping them into the same petri dish! No projections necessary!
Somehow, the retina is sending out signals that can synchronize the SCN. What it is sending out? Hormones? Neurotransmitters? Magic powers? No one knows.
For now, though, it might be best to just keep syncing with sunlight. >_<