Mind & Brain

Every year, like clockwork, DISCOVER digs through reams of newspapers and gigabytes of Web sites to find the 100 most important and interesting science stories of the year. We're unveiling the top stories from 2006 over the next couple of weeks, one subject at a time. Here's the whole list (only subscribers get access to the whole special package immediately).

Also check out the results of our year-in-science poll, in which readers chose Pluto Demoted as the biggest story of the year.

17 Man Recovers From Near-Coma After Two Decades
For 19 years after a car accident, Terry Wallis lingered speechless...

33 Looks Can Kill
Black defendants are more likely to receive the death penalty. It's also how black you look...

43 IQ Linked to Brain Structure
Embryonic stem cells helped rats suffering from Parkinson's-like symptoms...

58 Why We Are Not Chimps
Humans and chimpanzees are about 98 percent alike, yet the human brain is three times bigger and far more complex...

70 Stroke Injury Shows New Way to Kick the Habit
The brain damage caused by certain strokes may eliminate an addiction to nicotine...

72 Source of Empathy Found
Mirror neurons fire when you watch other people act...

For 19 years after a car accident that caused severe brain damage, Terry Wallis lingered speechless in a minimally conscious state, a limbo only a few steps up from a coma. Then one day in 2003, he stunned his mother by calling her "Mom" and, over the next few days, regaining the ability to talk. Nicholas Schiff, a neurologist at Weill Medical College in New York City, was amazed when he examined Wallis's brain eight months later.

Courtesy of the Journal of Clinical Investigation

In July Schiff and his colleagues reported that Wallis's brain was badly atrophied—but it had not been idle. Using a technique called diffusion tensor imaging, which can spot neural connections, the researchers saw what appeared to be massive tracts of new axon growth. Wallis's brain had been rewiring itself.

During the year after he regained his speech, Wallis continued to improve, recovering some use of his limbs. A second scan made 18 months after the first one found that his brain was still changing. The first exam had seemed to show thick areas of new connections in the rear cortex of his brain, a region linked to awareness. A year and a half later, those areas looked more normal, and the cerebellum, which controls motor function, showed major changes, consistent with his recent physical improvement.

Schiff's ongoing studies of Wallis and his astounding recovery may transform our understanding of the brain's ability to heal itself. Neurologist Steven Laureys of the University of Liège in Belgium, who has studied similar cases, says, "This is very welcome, because there's so little we know about these late recoveries."

Kathleen McGowan

What does it mean to be conscious? Try getting into the brain of a cockroach to find out.

Courtesy of the Michigan State Police Department

Study after study has shown that black defendants are more likely than white ones to receive the death penalty. But according to a paper published in Psychological Science in May, it's not just whether you're black that matters in capital sentencing; it's also how black you look.

After gathering photos of defendants eligible for the death penalty, all convicted in Philadelphia between 1979 and 1999, Stanford University psychologist Jennifer Eberhardt and her team asked students to rate how "stereotypically black" each person looked. The subjects knew only that they were seeing pictures of black men, not criminals. The researchers then compared the "blackness" ratings with the convicts' sentences.

Eberhardt found that 57.5 percent of defendants rated as stereotypically black (with traits including darker skin and a broader nose) had received the death penalty, compared with only 24.4 percent of those judged less stereotypically black. These percentages held only when the victim was white. Eberhardt speculates that black-on-white cases cause jurors to think about the crime as a conflict between races, not individuals. As a result, race becomes an extra factor in their decision making.

Marina Krakovsky

As odd as it may sound, African Americans also have statistically more trouble quitting smoking than other races. Find out why.

Scientists have long sought a connection between intelligence and some structure in the brain. In March they finally found a significant correlation, one seen only during childhood development.

The brain's cortex, where complex reasoning occurs, can begin to thicken with the approach of adolescence, then thin again toward its end. The pattern correlates with a child's IQ scores, says psychiatrist Jay Giedd of the National Institute of Mental Health. In smarter children, the cortex grew more quickly and thinned more quickly over the course of the study. In kids of average intelligence, certain parts of the cortex showed steady thinning right from the start.

How much of this is inherited? "The impact of the brain interacting with the environment during this time of plasticity is the key," Giedd says. "It's very hard to sort out all the family influences and varying educational opportunities."

Nicholas Bakalar

Why did evolutionary pressure make our cortexes so wrinkly? Unravel the mystery by reading Shanti Menon's piece.