Hey there. I'm Josh Clark and this is BrainStuff,and this is the BrainStuff where I talk to you about seeing stars. So have you ever seen some lights appear inyour field of visioné And you were kind of certain they weren't really thereéAnd insteadof coming closer and eventually landing and kicking off a really weird experience whereyou ended up abducted and probed and then dumped in the woods. that didn't happené And instead these lights went away, they wereprobably phantomsé Well then you, my friend, saw what are called 'phosphenes.'
Phosphenes are lights that aren't really there.They're the result of your visual system being fooled in some shape or fashion. And yourvisual system itself consists of about three main parts. You've got your retina, which are the lightsensitive cells in the back of your eye that pick up photons from the environment. You've got the optic nerve, that takes theelectrochemical signal that your retina translates the photons into, and carries it up to yourbrain. Then you've got the occipital lobe, whichis the first initial sorting center for visual
stimulation. You put all these things together and somethinggoes from, quot;I see a blob of color,quot; to quot;I see pizza!quot; So phosphenes again, these phantom lights can be produced any time any part of your visual system is manipulated. And there'stwo main ways they can be manipulated: mechanical and electrical. Electrical stimulation is basically where,say, you take an electromagnet and run it past your occipital lobe you can producephosphenes. It's also been shown to produce
phosphenes when you take electrodes and implantthem near your optic nerve. You can actually produce phosphenes in people who are blindbecause of a retinal malfunction. That means that the rest of their visual system is working,and if you stimulate it electrically, you can produce these phantom lights. Which ispretty awesome. There's also mechanical stimulation, whichis like when your rub your eyes like Tom or Jerry. You can also produce it when you pressthe side of your eye very gently and slowly toward your nose. It will eventually producephosphenes. You can go ahead and do it just do it gently.
Mechanical stimulation can also be inducedin the occipital lobe itself, specifically if somebody hits you over the back of yourhead with a guitar and your brain slaps around your skull in that area. The neurons, stimulatedsuddenly, are fooled into thinking that they are sensing something, and maybe getting anelectrochemical signal from the optic nerve. You can also see stars from things like sneezing,which is pressure induced, kind of like pressing on your eye. There's also something that hasto do with blood pressure, although it's not quite clear why. Where if you stand up quickly,you feel a little faint and you start to see starsé It's probably from a change in theoxygen available to either your retinal cells,
optic nerve, or your neurons. And there's other ways phosphenes can be producedtoo, like, for example, drugs. Or if you lack any kind of visual stimulation, like you'rea long distance trucker or a pilot flying at night. You can start to hallucinate phosphenes. So should you be worried if you see starséWell, if you've just been pressing your eye or you just sneezed and the stars come andgo pretty quickly, probably not. But if somebody did hit you over the backof the head and you're seeing stars, you should probably go to the ER, because you may havejust suffered a concussion.
Can Bright Light Make You Sneeze
About one third of the people on Earth willtell you that this is a thing. The other twothirds probably think that thefirst third is crazy, but they're too polite to say anything. But if you've ever walked out of dark matineetheater, or driven out of a long tunnel and into the sunlight, and then suddenly SNEEZED,you're probably experiencing one of medical science's leastunderstoodbutthankfullyharmlessphenomena. It's known as photic sneezing or sneezingtriggered by sudden exposure to bright light. And it happens to about 30 to 35 percent ofus.
So take that all you naysayers! It's real!But scientists don't know why. References to lighttriggered sneezing showup in medical literature as far back as Aristotle. But modern researchers started looking intoit more closely, when they realized that a poorly timed photic sneeze could pose a bigproblem for people like surgeons and airplane pilots. So far, the best we can figure is that lighttriggeredsneezing has to do with an interaction between overactive sensory nerves. A study in 2010, for instance, examined tenphotic sneezers, as well as a control group.
After exposing all of the subjects to bright,flashing light, the researchers found that the light triggered a lot more activity inthe visual cortex of the photic sneezers' brains than in the control group. So it couldjust be that sneezers' sensitivity to light is just more excitable than in other people. But the prevailing theory has to do with aspecific, complex nerve bundle called the trigeminal nerve, which is the biggest nervein your head. It is responsible for all of the sensationin your entire face, from the tickle in your nose to the twitch in your eyebrows to thatfeeling of needing Chapstick.
And parts of this nerve also sidle up niceand close to your optic nerves, which transmit the information your brain gets about lightentering your eyes. So the theory is that a sudden flash of brightlight stimulates the optic nerve, which sometimes also transmits an impulse to the nearby branchesof the trigeminal nerve that connect to the nose and mouth. This impulse mimics the tickle of a nasalirritation, which then causes you to sneeze. So while we're not exactly sure about howit works, this scenario might explain why other weird things can trigger sneezing thatalso involve stimulating the trigeminal nerve
like pulling hair, or plucking eyebrows. So if you're a photic sneezer, there's noneed to hide it anymore. Be proud! Thanks for asking, especially to our Subbablesubscribers who keep these answers coming! And if you have a quick question, let us knowon Facebook and Twitter or in the comments below, and don't forget to go to YouTube SciShowand subscribe!.