The Amazing Teen Brain

88 Pages·2015·17.65 MB·English

ASTRONOMY TECHNOLOGY MEDICINE
All the Light Our Best Treatments for
There Ever Was Chance for Mars? Cells on Fire
ScientificAmerican.com
JUNE 2015

The
Amazing
Teen Braın
Rapidly changing
wiring leads to
mental agility—
and risky
behavior
© 2015 Scientific American

ON THE COVER
Teenage behavior is all over the map. For years neuro­
scientists (and parents) have been baffled as to why. Exten­
sive MRI studies are revealing that underneath the tri­
umphs and pitfalls of teen life are sweeping changes in the
networking of brain regions. The new knowledge could
help teens avoid mental illness and make smart choices for
June 2015 Volume 312, Number 6
a bright future. Illustration by FOREAL.
56
FEATURES
NEUROSCIENCE ETHOLOGY
32 The Amazing Teen Brain 50 The Networked Animal
Why are adolescents prone to risky behavior and Who knows whom matters, not only in human societies
mental illnesses? And why are their minds so agile but among the animals as well.
and teachable? It’s all in their rapidly changing wiring. By Lee Alan Dugatkin and Matthew Hasenjager
By Jay N. Giedd
TECHNOLOGY
ASTRONOMY 56 Birth of a Rocket
38 All the Light There Ever Was To some, nasa’s Space Launch System is a gigantic piece
Astronomers have started measuring background light of congressional pork. It may also be our best shot at
that dates back to nearly the beginning of time. Now getting humans to Mars. By David H. Freedman
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Forensic scientists are working to trace the identities of
MEDICINE
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Scientists have discovered how cells trigger inflam­ PUBLIC HEALTH
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© 2015 Scientific American

From the Editor
Mariette DiChristina is editor
in chief of Scientific American.
Follow her on Twitter @mdichristina
Promises and Perils
L
istening to my 14-year-old daughter explain her those that handle so-called executive function, which mature in a
writing assignment the other night, I was surprised person’s 20s. Giedd also describes how an earlier onset of puber-
to learn we both had similar homework. I was about ty in recent decades has ext ended this angst-ridden period.
to start this letter to introduce the current issue and The protracted maturation, however, beneficially creates
its cover story, “The Amazing Teen Brain,” by psychi- prolonged plasticity—enabling teenagers’ enviable leaps of cog-
atrist Jay N. Giedd. Her essay was goi ng to analyze the nition and ada ptability, for example, to today’s
reasons behind the rash behavior of the famous data-enriched world. Both traits have served
star-crossed young lovers in Shakespeare’s Ro- our species well in the past. Now, as science
meo and Juliet. As she explained, “Teenagers’ provides a better understanding of this
brains are not fully developed yet, so they powerfully influential developmental win-
have a problem with impulse control.” As dow, society—from parents to policy lead-
she dispassionately talked about the brains ers to youngsters themselves—can work
of people her own age, I was struck anew together to support teens on their jour-
by how grown-up teens can seem. ney. For the full story, turn to page 32.
At the same time, as we are reminded Rather than soaring into the future,
painfully and too frequently not only by the Space Launch System, a successor to
fictional plays but also by real-world the shuttle, has been called a “rocket to
headlines, adolescents are uniquely vul- no where”—a congressional jobs pro-
nerable to risky behavior, leading to mis- gram with little hope of actually flying
haps or to recruitment to violent ends as to space. But in “Birth of a Rocket,”
soldiers or even terrorists. A key question around the recent tri- starting on page 56, journalist David H. Freedman takes a look
al of Dzhokhar Tsarnaev, who was 19 at the time of the Boston at how the system, which is on time and on budget for a 2018
Marathon bombing, for instance, was the degree to which he flight, could actually bec ome the vehicle of choice to reach
was under the influence of his 26-year-old brother, Tamerlan. Mars in about 25 years. Given the sufficient political will—no
At root is a developmental mismatch be tween the mental net- small hurdle—the teens of today could see humans step onto
works that manage emotion, which shift rapidly at puberty, and another planet.
BOARD OF ADVISERS
Leslie C. Aiello Kaigham J. Gabriel Lawrence M. Krauss Martin A. Nowak Terry Sejnowski
President, Wenner-Gren Foundation President and Chief Executive Officer, Director, Origins Initiative, Director, Program for Evolutionary Professor and Laboratory Head
for Anthropological Research Charles Stark Draper Laboratory Arizona State University Dynamics, and Professor of Biology and of Computational Neurobiology Laboratory,
of Mathematics, Harvard University Salk Institute for Biological Studies
Roger Bingham Harold “Skip” Garner Morten L. Kringelbach
Co-Founder and Director, Director, Medical Informatics and Robert E. Palazzo Michael Shermer
The Science Network Systems Division, and Professor, Virginia Director, Hedonia: TrygFonden Dean, University of Alabama at Publisher, S keptic m agazine
Bioinformatics Institute, Virginia Tech Research Group, University of Oxford Birmingham College of Arts and Sciences
Arthur Caplan and University of Aarhus Michael Snyder
Director, Division of Medical Ethics, Michael S. Gazzaniga Carolyn Porco Professor of Genetics, Stanford
Department of Population Health, Director, Sage Center for the Study of Mind, Steven Kyle Leader, Cassini Imaging Science University School of Medicine
NYU Langone Medical Center University of California, Santa Barbara Professor of Applied Economics and TSepaamce, aSncdie Dnciree Icntsotri,t uCtIeCLOPS, Michael E. Webber
David J. Gross Management, Cornell University Co-director, Clean Energy Incubator,
Vinton Cerf
Professor of Physics and Permanent Vilayanur S. Ramachandran and Associate Professor,
Chief Internet Evangelist, Google Member, Kavli Institute for Theoretical Robert S. Langer Director, Center for Brain and Cognition, Department of Mechanical Engineering,
George M. Church Physics,University of California, Santa David H. Koch Institute Professor, University of California, San Diego University of Texas at Austin
Director, Center for Computational Barbara (Nobel Prize in Physics, 2004) Department of Chemical Lisa Randall Steven Weinberg
Genetics, Harvard Medical School Lene Vestergaard Hau Engineering, M.I.T. Professor of Physics, Harvard University Director, Theory Research Group,
Rita Colwell Mallinckrodt Professor of Lawrence Lessig Martin Rees Department of Physics,
Distinguished University Professor, PHhayrsviacrsd a Undn iovfe Arspitpylied Physics, Professor, Harvard Law School Astronomer Royal and Professor (UNnoivbeerl sPitryiz oef iTne Pxhays saict sA, u19st7i9n)
University of Maryland College Park of Cosmology and Astrophysics,
and Johns Hopkins Bloomberg School Danny Hillis John P. Moore Institute of Astronomy, University George M. Whitesides
of Public Health Co-chairman, Applied Minds, LLC Professor of Microbiology and of Cambridge Professor of Chemistry and
Richard Dawkins Daniel M. Kammen Immunology, Weill Medical John Reganold Chemical Biology, Harvard University
Founder and Board Chairman, Class of 1935 Distinguished Professor College of Cornell University Regents Professor of Soil Science Nathan Wolfe
of Energy, Energy and Resources Group, and Agroecology, Washington Director, Global Viral Forecasting Initiative
Richard Dawkins Foundation M. Granger Morgan
and Director, Renewable and Appropriate State University
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4 Scientific American, June 2015 Illustration by Nick Higgins
© 2015 Scientific American

Letters
[email protected]
“ It would be wise liances” would be historically unlikely.
The most likely scenario would involve
for us to give up
waves of immigrating anatomically mod-
the notion that ern humans taking over land and causing
death by plunder and disease, as Europe-
we are a benevolent
ans discovering the New World did. And it
and sharing species.” would be naive to think that our Neander-
tal DNA was the result of consensual dalli-
robert e. marx u niversity of miami
miller school of medicine ances when rape went hand in hand with
the pillage of every other civilization.
It would be wise for us to give up the
atable than population controls, which notion that we are, or our ancestors before
are objectionable on many levels. us were, a benevolent and sharing species.
Robert E. Marx
BLACK HOLE BIZARRENESS University of Miami
I agree with Adam Brown’s crazy but fun Miller School of Medicine
article—“Can We Mine a Black Hole?”—
that it is physically impossible to rapidly NEANDERTAL SPELLING
February 2015 mine black holes for energy. There are The cover of the issue and Wong’s article
many other “catches” that he does not refer to “Neandertals.” So is the spelling
mention, however. One is that the more for “Neanderthal” now without an “h”?
PRIORITIZING POPULATION massive a black hole is, the colder it is, and Steve Larios
In “A Puzzle for the Planet,” Michael E. a black hole with a mass greater than via e-mail
Webber discusses the need to integrate about one tenth of that of Earth will have a
three key factors (energy, water and food) temperature lower than that of the cosmic THE EDITORS REPLY: G erman linguistic
to make it possible to meet the needs of a microwave background (CMB), which is reforms in the early 1900s changed the
growing population. A critical point is that about 2.73 kelvins. Any black hole with spelling of the name of the Neander Valley
we have to stabilize that population in the greater mass will therefore gain energy from “Neander Thal” to “Neander Tal”
first place. As long as it continues to grow, from the CMB and get more massive (and (the “h” was silent). Today the common
all other efforts are merely stopgaps. hence, oddly, colder). Only lighter, smaller name of these extinct humans can be
Avi Ornstein black holes radiate, getting lighter and hot- spelled with or without the “h.” Scientific
New Britain, Conn. ter as they do so, until they explode in a American has long favored “Neandertal.”
sudden burst of particles. So find a micron-
WEBBER REPLIES: P opulation growth is size black hole but do not go close to it!  MEMRISTOR NETWORKS
indeed important, but it turns out that eco- Michael Albrow In “Just Add Memory,” Massimiliano Di
nomic growth is a bigger deal: demand for Fermi National Accelerator Laboratory Ventra and Yuriy V. Pershin talk about
food, energy and water are growing faster how a network of memristors—comput-
than population because people tend to de- BROWN REPLIES: T he CMB is indeed ing components that change electrical re-
mand more meat and electricity (both of much hotter than a solar-mass black hole, sistance in response to the amount of
which are water-intensive) as they are ele- but it won’t be for long. Because the universe current and retain that change—can
vated out of poverty. The average Chinese is expanding, the temperature of the CMB is solve a maze problem in one step. They
citizen, for instance, consumes about a falling; thanks to dark energy, it is falling fail to mention that to appropriately
fourth of the energy of a typical U.S. citi- exponentially, halving every 10 billion “wire” the memristors in the maze, so
zen, and as the former becomes richer, that years or so, and will soon (relatively speak- that an input is connected to an output,
gap narrows. (Meanwhile urbanization, ing!) be much colder than any black hole. each square of it would need to be visited
which reduces birth rates, is increasing.) and a memristor placed where needed.
Therefore, making sure that people OUR MURDEROUS ANCESTORS Doing so may require more of the maze to
have the energy, water and food they need Kate Wong’s suppositions about what be visited than a random drunkard’s walk
for a free and prosperous life, without all brought about Neandertals’ extinction solution or the classic right-hand-to-the-
the environmental and security challeng- in “Neandertal Minds” are contrary to wall solution.
es that plague our old approaches, is the the known history of anatomically mod- Dave Brumley
most effective place to start. Plus, the poli- ern Homo sapiens ( that is, us). Her as- San Diego
cy levers (investing in new technologies, sertions that Neandertals were just out-
reinventing markets and pushing for a competed and that the 1.5 to 2.1 percent THE AUTHORS REPLY: T o create a maze,
culture of conservation) for solving this Neandertal DNA within people outside the only thing you need to know is the
nexus are more straightforward and pal- of Africa is the result of occasional “dal- maze topology—namely the position of the
6 Scientific American, June 2015
© 2015 Scientific American

Letters
LETTERS TO THE EDITOR
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