Scientific American Special Edition 2023 Spring.pdf

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SPECIAL COLLECTOR’S EDITION
The Brain
How this amazing organ defines our reality
and helps us sense, think and act
I N S I DE
How teen
brains work
Why we sleep
Our individual
consciousnesses
Long COVID:
neurological disorder
Babies can do math
SPRING 2023
Dreams can
foreshadow disease
© 2023 Scientific American
ESTABLISHED 1845
The Brain
is published by the staff of
Scientific American, with
project management by:
Editor in Chief:
Laura Helmuth
Managing Editor:
Jeanna Bryner
Chief Newsletter Editor:
Andrea Gawrylewski
Creative Director:
Michael Mrak
Issue Designer:
Lawrence R. Gendron
Senior Graphics Editor:
Jen Christiansen
Associate Graphics Editor:
Amanda Montañez
Photography Editor:
Monica Bradley
Issue Photo Researcher:
Beatrix Mahd Soltani
Copy Director:
Maria-Christina Keller
Senior Copy Editors:
Angelique Rondeau, Aaron Shattuck
Associate Copy Editor:
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Managing Production Editor:
Richard Hunt
Prepress and Quality Manager:
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Executive Assistant Supervisor:
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Senior Editorial Coordinator:
Brianne Kane
The Final Frontier
Is Right Here
The human brain is a powerhouse.
The Milky Way galaxy has hundreds of billions of stars—
just a
fraction
of the 100 trillion connections in our brains that enable us to sense, think and
act. Our minds are the result of countless neuronal firings that happen every millisecond.
Across animals, brain size is usually tightly correlated with body size—the encephalization
quotient, as it’s called. Elephants score a 1 or 2 on this measure, long-finned pilot whales 2 to
3. Humans? We score between 7 and 8. Among the gains from this outsize brain is the work of
neuroscientists, philosophers and
even poets. Read this collection for
a look at the most astounding re-
cent brain discoveries.
Consciousness is perhaps hu-
mans’ most complex aspect. Our
perception of the world builds our
individual realities—and no two
are alike (
page 12
). The ventrome-
dial prefrontal cortex may produce
a fundamental model of the self
and knit together versions of us
from past and present—even pro-
jecting into the future (
page 30
).
New discoveries for detecting con-
sciousness in comatose people illu-
minate the remarkable persistence
Branching and tangled neuronal cells fire countless times
every millisecond.
of the mind (
page 24
).
We are self-aware, yes. But how
does that awareness integrate with a complicated and ever-changing world? A nonstop scan-
ning and filtering system in the brain selects the most essential elements from our surround-
ings to help us thrive (
page 32
). Special brain regions are activated to help us physically navi-
gate our surroundings (
page 62
) and recognize faces (
page 54
). From birth we have an innate
ability with numbers (
page 40
), and we grow into a period of adolescence marked by sensitiv-
ity to social cues and community acceptance (
page 48
).
As with any complex machine, errors can arise. Leaks in the protective blood-brain barrier
can trigger events leading to Alzheimer’s disease and other dementias—a process that scien-
tists are urgently trying to prevent (
page 68
). Acting out dreams can be a telltale early sign of
brain disorders (
page 88
). Even viruses such as the one that causes COVID can produce last-
ing neurological problems, although precisely how is a fresh area of study (
page 74
).
The brain is wonderfully self-sustaining, even after many decades of firing away. Important
maintenance includes getting ample sleep, which neuroscientists now believe flushes toxins
and helps to consolidate memories (
page 98
). A positive attitude may affect how well our
immune systems function (
page 104
). And here’s both bad and good news on aging and the
brain: after we turn 65, our risk of dementia increases (
page 96
), but stress seems to have less
of an effect on our happiness (
page 110
).
Around the beginning of the 20th century Santiago Ramón y Cajal—the father of mod-
ern neuroscience—described neurons, the branching and tangled cells that make up brain
matter, as “mysterious butterflies of the soul.” More than 100 years later the enigma and
marvel of the human brain endures. We know much more than when he first looked through
his microscope and eyed that mystery. For some, the final frontier will be not in the reaches
of space but as close as can be.
Andrea Gawrylewski
Chief Newsletter Editor,
editors@sciam.com
FROM THE EDITOR
President:
Kimberly Lau
Publisher and Vice President:
Jeremy A. Abbate
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Dan Benjamin
Vice President, Commercial:
Andrew Douglas
Vice President, Content Services:
Stephen Pincock
Associate Vice President,
Business Development:
Diane McGarvey
Programmatic Product Manager:
Zoya Lysak
Product Managers:
Ian Kelly, Miguel Olivares
Head, Marketing:
Christopher Monello
Mark Ross Studios (
cover illustration
);
Bruce Rolff/Stocktrek Images/Getty Images (
this page
)
Senior Commercial Operations Coordinator:
Christine Kaelin
Custom Publishing Editor:
Lisa Pallatroni
Senior Communications Manager:
Sarah Hausman
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Madelyn Keyes-Milch
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SCIENTIFICAMERICAN.COM
|
1
SPECIAL EDITION
Volume 32, Number 2, Spring 2023
HOW
CONSCIOUSNESS ARISES
4
How Matter Becomes Mind
The new discipline of network neuroscience
yields a picture of how mental activity arises from
carefully orchestrated interactions among different
brain areas.
By Max Bertolero and Dani S. Bassett
74
The Brain and Long COVID
Millions of people are still suffering long after infection.
Now researchers are finding neurological causes for
their symptoms.
By Stephani Sutherland
82
A Talking Cure for Psychosis
Cognitive-behavioral therapy helps to treat symptoms
for which drugs are ineffective.
By Matthew M. Kurtz
12
Our Inner Universes
Reality is constructed by the brain, and no two brains
are exactly alike.
By Anil K. Seth
88
When Dreams Foreshadow Brain Disease
Acting out dreams is one of the earliest signs
of  Parkinson’s disease.
By Diana Kwon
18
The Brain Electric
Electrodes that stimulate brain tissue reveal the
topography of conscious experience.
By Christof Koch
96
Mental Illness and Dementia
Why do psychiatric conditions multiply the risk
of  cognitive decline?
By Claudia Wallis
24
Hidden Consciousness
Some patients who appear to be in a coma, and
can’t speak or move, may be aware of what is happening
around them.
By Jan Claassen and Brian L. Edlow
97
Aneurysm in a Dish
Scientists operate on a 3-D-printed model of a ballooning
blood vessel.
By Tanya Lewis
30
Creating Our Sense of Self
One brain region helps people maintain a consistent
identity.
By Robert Martone
HEALTHY BODY,
HEALTHY BRAIN
98
Deep Sleep Gives Your Brain a Deep Clean
Slow-wave activity during dreamless slumber
helps to wash out neural detritus.
By Simon Makin
MAKING SENSE
OF THE WORLD
32
Constructing the World from Inside Out
The brain probes your physical surroundings to select
just the information needed to survive and flourish.
By György Buzsáki
102
Exercise Pill
Isolated proteins might one day produce health gains
without the exertional pain.
By Emily Willingham
40
Born to Count
As Plato anticipated, babies do math.
By Jacob Beck and Sam Clarke
104
Brain over Body
Scientists are deciphering how the brain choreographs
immune responses, hoping to find treatments for
a  range of diseases.
By Diana Kwon
48
Age of Opportunity
A refined understanding of the adolescent brain could
lead to improvements in education and mental health.
By Lydia Denworth
110
Growing Older Means Less Stress
Good news: people report that worries and anxiety
decline as they age.
By Daisy Yuhas
54
Face Values
Brain regions that process faces reveal deep insights
into the neural mechanisms of vision.
By Doris Y. Tsao
DEPARTMENTS
1
FROM THE EDITOR
The Final Frontier Is Right Here
112
END NOTE
The Secrets of Thirst
Your body usually knows how much water you need,
without arbitrary targets.
By Claudia Wallis
Articles in this special issue are updated or adapted from previous issues of
Scientific American
and from ScientificAmerican.com and
Nature.
Copyright © 2023 Scientific American, a division
of Springer Nature America, Inc. All rights reserved. Scientific American Special (ISSN 1936-1513),
Volume 32, Number 2, Spring 2023, published by Scientific American, a division of Springer Nature
America, Inc., 1 New York Plaza, Suite 4600, New York, N.Y. 10004-1562. Canadian BN
No. 127387652RT; TVQ1218059275 TQ0001. To purchase additional quantities: U.S., $13.95 each;
elsewhere, $17.95 each. Send payment to Scientific American Back Issues, P.O. Box 3187, Harlan,
Iowa 51537.
Inquiries: fax 212-355-0408 or telephone 212-451-8415. Printed in U.S.A.
62
The Brain’s Social Road Maps
Neural circuits that track our whereabouts in space
and time may also play vital roles in determining
how we relate to other people.
By Matthew Schafer and Daniela Schiller
BRAIN
DISORDERS
68
Holes in the Shield
Leaks in a protective filter called the blood-brain barrier
may lead to Alzheimer’s and other dementias. Reversing
the effects makes aging animal brains look young
and healthy.
By Daniela Kaufer and Alon Friedman
2
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SCIENTIFIC AMERICAN
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SPECIAL EDITION
|
SPRING 2023
© 2023 Scientific American
Viktor Koen
Zara Picken
© 2023 Scientific American
Richard Borge
Lara Santos/Veiga-Fernandes Lab
68
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104
SCIENTIFICAMERICAN.COM
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