www.sc iammind.com

Integrating Newbies

A common neurotransmitter that conveys signals among brain cells reverses its normal function to accommodate new neurons in the brain.

Since the remarkable 1998 discovery that people can grow new neurons well into old age, researchers have wanted to know how the newbies integrate themselves gracefully into existing neural networks without causing interference. Studies in embryonic rodents and monkeys suggested that the neurotransmitter GABA, which normally inhibits neurons from fi ring, may instead be stimulating young neurons to fi re.

Sparked by this clue, a group at Johns Hopkins University turned to a part of the hippocampus called the dentate gyrus. In a common strategy for visualizing new neurons, they introduced a retrovirus into mice that makes dividing neurons fl uoresce green. They then measured the responsiveness of these cells to different neurotransmitters.

Initially the new neurons were sensitive to GABA that had diffused into the space between cells. After a week the new cells connected to established neurons, which transmitted GABA in pulses. In another week the cells formed connections to receive glutamate, the major stimulatory neurotransmitter in adult neurons. The results indicate that despite differences between embryos and adults, “newly formed neurons must follow this sequence,” says Yehezkel Ben-Ari, director of the Mediterranean Institute of Neurobiology in France, who is not connected to the Johns Hopkins work.

Apparently, an excess of chloride ions inside the young cells is responsible for their excitation by GABA. Chloride-defi cient neurons that the scientists engineered showed a two-week delay in developing connections and eventually died. Johns Hopkins neuroscientist Hongjun Song says the team hopes to test whether applying GABA to stem cells at the right time and dose could help repair central nervous system injuries. —JR Minkel

Discipline Pays

Any teacher can tell you that smarts alone do not a good student make. But psy-chologists had never rigorously studied the connection between self-discipline and aca-demic success, says former teacher Angela L. Duckworth, now a psychology graduate student at the University of Pennsylvania. Duckworth and her adviser, Martin E. P. Seligman, gave 300 eighth graders, their teachers and their parents a questionnaire about the students’ ability to control impulses and fol-low rules. They also gave the chil-dren another questionnaire and behavioral test to assess their willingness to delay gratifi cation. The reported self-discipline pre-dicted fi nal grades, school atten-dance and work habits better than IQ did. Moreover, the stronger

the discipline, the better the outcomes.The results could encourage young

students to toe the line. Still, the research method may not be practical for routinely evaluating children, Duckworth says. “The effort that’s involved in a study like this is kind of humongous.” —JR Minkel

■ Fish is brain food. Although many dietary wives’ tales have no basis in science, this one apparently holds up. Recent studies show that six-month-old babies whose mothers ate more fi sh during their second trimester of pregnancy score higher on cognitive tests, and senior citizens who eat fi sh at least once a week do better on memory and mental acuity exams than peers who do not.

■ The widower effect is strikingly real, according to a massive study released in February by Harvard Medical School and the University of Pennsylvania. For nine years, researchers followed more than 518,000 couples older than 65. The death of a wife in the previous 30 days increased a husband’s risk of death by 53 percent, and the death of a husband increased a wife’s risk of death by 61 percent. Additionally, the hospitalization of one partner elevated health risks for the other partner for nearly two years.

■ Bartenders, as well as drinkers at home, unintentionally pour 20 to 30 percent more liquor into short, wide glasses than tall, slender ones when making a mixed drink. Economics profes-sor Brian Wansink of Cornell University ex-plains that people per-ceive tall glasses as hold-ing more than short ones of the same volume—an optical illusion. They also focus on the level of the liquid, insuffi ciently compensating for its diameter and thus the total volume.

—————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————FLASHF

RO

M “

GA

BA

RE

GU

LA

TE

S S

YN

AP

TIC

IN

TE

GR

AT

ION

OF

NE

WLY

GE

NE

RA

TE

D N

EU

RO

NS

IN

TH

E A

DU

LT B

RA

IN,”

BY

SH

AO

YU

GE

ET A

L.,

IN

NA

TU

RE

, V

OL

. 4

39

; F

EB

RU

AR

Y 2

, 2

00

6,

RE

PR

INT

ED

BY

PE

RM

ISS

ION

FR

OM

MA

CM

ILL

AN

PU

BL

ISH

ER

S L

TD

. (t

op

); D

AV

ID W

OO

LL

EY

Ge

tty

Ima

ge

s (b

ott

om

)

New neurons do not integrate (far left) until stimulated by GABA (remaining images).