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Science notes / Neuroscience

Inside a pigeon's brain

Homing pigeons, the earliest form of email, can find places thousands of miles away because of nerve cells in their brain stems that react to magnetic sensors that may be located elsewhere around their head, a study finds.

Scientists have long known that the birds navigate using the earth's magnetic field. The latest research, reported last week in the journal Science, has uncovered subtle mechanics in the brain that allow pigeons to find their way home even when the sky's directional markers are hidden by clouds.

Pigeons were released in a black room with an artificial magnetic field that was manipulated by scientists, who used electrodes to determine which neurons were firing. They found that different neurons in the brain stem became active, depending on the direction of the magnetic field. That's what helps the birds determine latitude, half the information needed to navigate, said J. David Dickman, at the Baylor College of Medicine in Houston.

"They've been used for centuries to carry news home," said Dickman, a study author. Pigeons brought from Central Park in New York to Texas would find their way back home. "It might take them a while, but they'd get there," he said.

It's still not clear how pigeons determine longitude, though the experiments show the birds have limited access to cardinal directions, according to Dickman. There may be intensity gradients to the earth's magnetic fields, he said.

-- Bloomberg News


Cracking under pressure

Everything starts out fine. And then, without warning, the dreck hits the fan and you're smoking cigarettes while eating a whole tub of ice cream, even though you know better. In "This Is Your Brain in Meltdown," in the April edition of Scientific American, three researchers explain the biological reactions that cause people to crack under pressure.

Until recently, scientists thought that when the going got tough, the hypothalamus -- an evolutionarily ancient structure at the base of the brain -- released a wave of hormones that sped up your heart rate, increased blood pressure and scrambled your thoughts. New research suggests this isn't the whole story. Stress actually has a lot to do with the prefrontal cortex, a more recently evolved area of the brain that controls our higher cognitive abilities.

During the onset of stressful events (important exams, approaching tigers, etc.) the prefrontal cortex shuts down, allowing the older components of our minds -- such as the amygdala, which helps regulate emotional activity -- to take the helm. In other words, our lizard brain gets to be in charge. Thus, our ability to perform complex actions is hindered, and it becomes tougher to control such impulses as the urge to down that whole tub of Ben & Jerry's.

-- Washington Post