Sneezing at the sun

From the consequential to the less so...

About a quarter of humanity will sneeze after being in the dark and then being exposed to the sun. Why we do this has yet to be understood, and, really, hasn't had much investigation, for understandable reasons. In this week's PLOS One, investigators from Switzerland tried to figure this out. In a simple experiment, they took ten known 'photic sneezers' and matched them by age and sex with non-photic sneezers. They then showed them a checkerboard display or a bright photic stimulus, and measured their electroencephalogram patterns.

Their findings? Photic sneezers, when exposed to a bright stimulus, had increased excitability of the visual cortex, not in the brainstem or lower centers of the brain, meaning that higher brain controls are responsible for this, not reflexive controls. Why some people photic sneeze and others don't and what this means in terms of neural pathways, remains unclear. Most importantly of all, however, I just learned that there is a proposed ACHOO acronym, meaning Autosomal Cholinergic Helio-Ophtalmologic Outburst, signifying the powers of acryonyms to confuse people even more.

Nicolas Langer*, Gian Beeli, Lutz Jäncke (2010). When the Sun Prickles Your Nose: An EEG Study Identifying Neural Bases of Photic Sneezing PLOS One