This time of year is a rough one is the Southeast. It’s a time of angiosperm related hyprocrisy. It’s so pretty outside that it cries out for Easter egg hunts, picnics, and other outside activities.
(it really does look like this)
Unfortunately, once the weather is warm for a few days, it looks like this.
(Sci’s car this morning, only it was worse than that. RUN FOR YOUR LIVES.)
As you might be able to imagine, this sort of thing means that the sneezing rate in the south has a remarkable uptick in the spring (though there’s no data on this, and compared to fall and summer allergies and winter colds, Sci might indeed just be spouting off lies right now).
But did you know that there are some people who will sneeze on a bright, sunny day, regardless of the pollen count? Did you know WHY?!
Langer et al. “When the Sun Prickles Your Nose: An EEG Study Identifying Neural Bases of Photic Sneezing” PLoS ONE, 2010.
And the best part of this study, what do you CALL the “photic sneeze reflex”?
ACHOO (Autosomal Cholinergic Helio-Ophtalmologic Outburst) syndrome. Some grad students who came up with this were probably giggling hysterically over their beers for this one.
(Sci would like to note that she sneezed no less than about 5 times during this write-up, though probably not due to sunlight)
According to the authors of this study, exposure to bright light, like sunlight, causes spontaneous sneezing in 24% of individuals! That’s a lot. Sci’s not really sure if this is a good sampling, though her’s isn’t much better, as she just asked around the lab about found a ratio closer to 1/6. But anyway.
The authors of this study wanted to determine what brain areas might be responsible for this effect. Sneezing is a reflex consisting of a big inhalation and a forced exhalation, and the locus for it in the brain may be along the spinal trigeminal nucleus, though that’s only been found in cats, not humans (also, it occurs to Sci that she really SHOULD write a post on the cranial nerves, because they are SO AWESOME. Someday). The reflex is triggered (we think) by somatosensory input coming from the nose saying that something is up in there.
So why on earth would your NOSE tickle when you’re exposed to sunlight?
To start to find this out, the authors of this study took a bunch of people with ACHOO syndrome (hehehehehe), and a bunch of controls. They put them in a chamber, and hooked them up to an electroencephalogram (EEG) to look at brain activity. Then they showed them a checkered box, followed rapidly by a burst of light, and checked out the brain activity. They used the EEG and a questionnaire to measure brain activity, and how much your nose tickled when you were exposed to bright sunlight.
This makes for some cool images.
What you can see up in the top section of the figure is the neural activation of the subjects around the light stimulus. You can see that there are several places where the sneezers’ brain activity was increased. And in the bottom of the figure you can see where. The sneezers show higher brain activity (in red) in the occipital lobe, which is an area of the brain which processes visual information.
They also looked at the prickle that the subjects felt in their noses when they were exposed to bright light. And that effect was even stronger.
You can see the red line above showing the photo sneezers had much higher nose-tickle response to bright light, and showed stronger activity in the somatosensory cortex, an area that processes sensory information. So it appears that people with ACHOO Syndrome have higher sensory responses to both the tickle sensation and to the visual stimulus of the bright light.
Unfortunately, they weren’t able to come up with a connection between the two areas and a sneeze reflex center (we’re not that good yet), but it’s certainly a first step, and the hypothesis is that the insula, may link the areas, though other pathways could exist as well (the insula is totally everyone’s favorite brain area right now, ain’t it?).
Now you might think: but how did they separate it out from the actual SNEEZE?! Sci wonders that, too, though it appears the neural stuff they got was fast enough that it wasn’t a problem, where was the SNEEZE?! What were the areas lighting up then? I’m sure there are a lot of them, but it’d still be a cool picture to see.
Langer N, Beeli G, & Jäncke L (2010). When the sun prickles your nose: an EEG study identifying neural bases of photic sneezing. PloS one, 5 (2) PMID: 20169159