brain hampster 

the hamster that runs on the wheel in your brain making thought possible

I can't think anymore, I think my brain hampster died!

brain hampster by lotuspanda March 15, 2008

Hamster Wheel Brain 

When your brain runs about some issue over and over again and won't stop, just like a hamster running in its exercise wheel. It keeps running, but doesn't get anywhere.

I'm having such hamster wheel brain about whether or not to take this job offer.

Hamster Wheel Brain by dward May 30, 2004

hamster-wheel brain

an instance of one's mind going over and over an issue or problem without finding a solution

I had a major case hamster-wheel brain today. I could not get organized and could not stop thinking about it.

hamster-wheel brain by The Return of Light Joker January 14, 2008