In the Wall Street Journal, the latest in the “do cell phones cause cancer/do bad things for your brain?” debate. What happened was interesting, but not exactly conclusive:

They conducted scans after subjects had cellphones held to their left and right sides for 50 minutes on two different days. The first day neither cellphone was turned on. The second day the right phone was activated but muted so the participants wouldn’t hear any noise. Because the participants didn’t know which phone was active, their expectations couldn’t skew the results.

The researchers found that some brain regions near the antenna became significantly more active when a cellphone was turned on and held to the ear, even though the participants didn’t speak or listen to a conversation, compared with when the phones weren’t activated.

The short version: cell phones, pressed against your head, do affect brain activity. Whether or not that’s a good, bad, or irrelevant thing, is still unknown.