Pleasant surprises tickle the brain

— -- With the descent of March Madness upon the basketball world, fans can once again anticipate the joy of an underdog triumph. It's one of life's rare joys, the astounding upset. From finding a nice parking space to winning the lottery, it seems everyone enjoys a pleasant surprise.

And why not? Your brain, it turns out, is deep-wired for enjoyment of unexpected rewards, finds a new study. Led by neuroscientist Kareem Zaghloul of the University of Pennsylvania, the study suggests that if you want a lesson to stick, an unexpected reward is what the brain is craving.

"The brain's sensitivity to unexpected outcomes plays a fundamental role in an organism's ability to adapt and learn new behaviors," write the study authors in the March 13 Science journal.

Monkey studies suggest these "unexpected outcomes" give a jolt to a particular part of the brain called the substantia nigra, twin darkly-colored bands of tissue that play a role in learning, addiction and voluntary motion. The dark color comes from being packed with "dopaminergic" brain cells, or neurons, sensitive to the brain chemical dopamine.

"The response of these neurons to rewards has not been directly measured in humans," write the study authors, doubtless due the difficulty in convincing volunteers (and hospital review boards) to have their brains wired open for science.

However, Zaghloul and colleagues had one set of patients who just might serve. The substantia nigra is the part of the brain affected by Parkinson's syndrome, which kills off dopaminergic neurons there, leading to tremors and a kind of paralysis.

So, the researchers asked six men and four women undergoing deep brain stimulation for Parkinson's to also take a learning test during the procedure to try and measure the response of their neurons to rewards.

In deep brain stimulation, surgeons implant an electrical "pacemaker" that sends electrical signals to parts of the brain, which has proven helpful in moderating Parkinson's symptoms. It's a serious surgery, approved for Parkinson's by the Food and Drug Administration in 2002, with side effects ranging from personality changes to bleeding in the brain.