Jon Hamilton

In order to see the red of a sunset or the green of spring leaves, developing human eyes need to get the right hormone at the right time.

That's the finding of a team of scientists who studied how color vision develops using hundreds of human retinas grown in the lab.

As a specialist in Alzheimer's prevention, Jessica Langbaum knows that exercising her mental muscles can help keep her brain sharp.

But Langbaum, who holds a doctorate in psychiatric epidemiology, has no formal mental fitness program. She doesn't do crossword puzzles or play computer brain games.

"Just sitting down and doing Sudoku isn't probably going to be the one key thing that's going to prevent you from developing Alzheimer's disease," she says.

Experiments with two gambling monkeys have revealed a small area in the brain that plays a big role in risky decisions.

When researchers inactivated this region in the prefrontal cortex, the rhesus monkeys became less inclined to choose a long shot over a sure thing, the team reported Thursday in the journal Current Biology.

Government scientists have presented new evidence that the plastic additive BPA isn't a health threat.

Low doses of the chemical given to hundreds of rats, "did not elicit clear, biologically plausible adverse effects," said K. Barry Delclos, a research pharmacologist at the Food and Drug Administration's National Center for Toxicological Research.

Kids with ADHD are easily distracted. Barn owls are not.

So a team at Johns Hopkins University in Baltimore is studying these highly focused predatory birds in an effort to understand the brain circuits that control attention.

The team's long-term goal is to figure out what goes wrong in the brains of people with attention problems, including attention deficit hyperactivity disorder.

Scientists have taken another step toward understanding what makes the human brain unique.

An international team has identified a kind of brain cell that exists in people but not mice, the team reported Monday in the journal Nature Neuroscience.

Chris Ferrari was just 18 the first time he balanced a rocket launcher on his right shoulder and aimed it at a practice target.

"Your adrenaline's going and you're trying to focus on getting that round to hit, and then you go to squeeze that trigger and, you know."

Boom!

The report is loud enough to burst the eardrums of anyone not wearing military-grade hearing protection. And the blast wave from the weapon is so powerful it feels like a whole-body punch.

There's new evidence that a woman's levels of female sex hormones, including estrogen and progesterone, can influence her risk of Alzheimer's and other forms of dementia.

Women are less likely to develop dementia later in life if they begin to menstruate earlier, go through menopause later, and have more than one child, researchers reported Monday at the Alzheimer's Association International Conference in Chicago.

Every day, Dr. Walter Koroshetz, 65, takes a pill as part of his effort to help keep his brain healthy and sharp.

The pill is his blood pressure medication. And Koroshetz, who directs the National Institute of Neurological Disorders and Stroke, says controlling high blood pressure helps him reduce his risk of dementia.

He also keeps his blood pressure down by exercising and paying attention to his weight and diet. "I'm a believer," he says.