Two years ago, I blogged about "earworms" -- songs you can't get out of your head. Apparently there are a lot of people out there suffering from this, because that posting is still on the first page of Google results for "earworms". But today I read about a study that helps explain why songs can become so firmly implanted.

A couple of researchers from Dartmouth University put some people in fMRI tubes, and scanned their brains while they listened to songs that were both familiar and unfamiliar; as you might imagine, there was all sorts of activity in the auditory cortexes. Then, the scientists would hit the "mute" button for a second or two. When the song was familiar, the subjects' auditory cortexes kept on firing -- as if the subjects were still hearing the songs. (In fact, when they were later asked about the experience, they reported still "hearing" the music even when it was briefly muted.) But when the song was unfamiliar? The subjects' brains didn't have that same level of activity, as the BBC reports. That seems to suggest that our brains get highly trained by a catchy, memorable song -- which is why it can feel like we can't get it out of our heads.

Interestingly, lyrics also made a difference. As Dartmouth officials reported in a press release:

The researchers also found that lyrics impact the different auditory brain regions that are recruited when musical memories are reconstructed. If the music went quiet during an instrumental song, like during the theme from the Pink Panther, individuals activated many different parts of the auditory cortex, going farther back in the processing stream, to fill in the blanks. When remembering songs with words, however, people simply relied on the more advanced parts of the auditory processing stream.

"It makes us think that lyrics might be the focus of the memory," says Kraemer.

(Thanks to Kottke.org for this one!)