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.

In the study, the researchers gave the patients a simple computer game to play and followed brain cell readings from microelectrodes inserted as part of the surgery. The computer game presented the patients with a red and blue deck of cards and told them that one deck paid out more money than the other. Their task in the five-minute game was to figure out which one was the winning deck. If the draw of a card yielded a reward, a stack of gold coins was displayed along with an audible ring of a cash register.

People may lie about what excites them, but neurons don't, the researchers conclude. Steady wins and losses from the card decks didn't draw any spike in brain activity, but sudden spates of big wins did. Similarly, "spike counts were also significantly greater in response to unexpected gains than to unexpected losses," the team found. The unexpected wins drew the brain's attention, with players quickly zeroing in on the high pay-off deck of cards.

"Our findings suggest that neurons in the human (substantia nigra) play a central role in reward-based learning," the researchers conclude. The joy of unexpected victory, it seems, may be a bunch of tiny cells staging a July 4th display in the middle of your head, in other words.

So don't blame the players from No-Name State or Anonymous Tech for pulling off more than one upset in a tournament game this March. Winning may be addictive, after all, with an unexpected reward delivering a powerful learning jolt to the brain.