Welcome to Your Child's Brain: How the Mind Grows From Conception to College (47 page)

Intervention is difficult for exactly the same reason that it is important: because it requires interrupting the developing brain’s strong tendency to match itself to the local environment. As we’ve discussed throughout this book, evolution has made that matching process resilient and hard to disrupt. If a child’s environment is toxic, though, it can do more harm than good. Fortunately, the reward for intervening is also large—turning that child into an adult who can function successfully in a safe and productive world, like the one we all want for our children.

ACKNOWLEDGMENTS

We could fill an elementary school auditorium with the people who made it possible for us to put together this book on children’s brains. Before and during its writing, so many people generously shared their friendship, experiences, expertise, and time. We are grateful to them all.

At home, Sandra thanks her husband, Ken, for his talented care and feeding of authors and for his enthusiastic contributions to adventures large and small. She would also like to thank her parents for their unwavering dedication to raising the individual child that she was, rather than trying to push her into pursuing their own aims.

Sam thanks his parents, Mary and Chia-lin (Charlie), for a lifetime of love, dedication, nurturing, and teaching. His wife, Becca, has been a partner in so many ways: our life and adventures, critical reading of every page of this book, and raising our irrepressible daughter, Vita, a source of delight and lessons for both of us. Becca and Vita were also good-humored about Sam jetting off to Sandra and Ken’s California eyrie for locavore cookery, long uphill and downhill conversation-filled walks, and the occasional bout of writing. Finally, the Princeton community of parents and colleagues was a great source of friendship, feedback, and support.

Lisa Haney and Patrick Lane again provided splendid illustrations, as they did for our previous book,
Welcome to Your Brain
. We are also grateful to Roger Tsien and Gordon Burghardt for permission to reprint photographs of chemistry apparatus and a playing turtle, and to Ken Britten for the image of what babies see.

For comments, conversation, anecdotes, and advice on various chapters, we are grateful to Ralph Adolphs, Robert Ammerman, Connie Ban, Daphne Bavelier, Dorothy Bishop, Gillian Blake, Paul Bloom, Ken Britten, Jeanne Brooks-Gunn, Silvia Bunge, Gordon Burghardt, BJ Casey, Anne Churchland, Karla Cook, Ricardo Dolmetsch, Chunyu (Ann) Duan, Barbara Edwards, Nancy Eskridge, Anne Fernald, Shari Gelber, Alan Gelperin, Anirvan Ghosh, Adele Goldberg, Alison Gopnik, Liz Gould, Charles Gross, Art Kramer, Eric London,
Bert Mandelbaum, Kim McAllister, Sara Mednick, Rebecca Moss, Rita Moss, Elissa Newport, Yuval Nir, Kathleen Nolan, Dan Notterman, Danielle Otis, Liz Phelps, Jessica Phillips-Silver, Emily Pronin, Robert Sapolsky, Steven Schultz, John Spiro, Lawrence Steinberg, Giulio Tononi, Marty Usrey, Anthony Wagner, and Jeffrey Wickens. By helping us with technical, medical, and child development facts and tone, they made us look better than we would have on our own. Needless to say, any remaining errors are our responsibility.

Our agent, Jim Levine, provided encouragement and reality checks as needed. He also helped us get in touch with Ellen Galinsky, who so kindly wrote a foreword that captures the spirit of the book. Beth Fisher didn’t let a worldwide recession get in the way of connecting us with publishers in other countries. Indeed, everyone we worked with at the Levine Greenberg Literary Agency was committed and enthusiastic at every turn.

Our editor, Ben Adams, believed in this book from its conception and never wavered in his support, all the way through delivery. Thanks to the entire Bloomsbury team for their help and suggestions, especially to managing editor Mike O’Connor for shepherding the manuscript through production calmly and carefully.

Finally, we are grateful to all the parents who unwittingly helped by asking us questions about their children’s brains. Your curiosity made this book worth writing. We hope you enjoyed it.

GLOSSARY

acetylcholine:
A neurotransmitter whose functions include activation of muscles, and which is released from neurons in the parasympathetic nervous system, as well as within the brain.

action potential:
A spikelike change in the voltage across the membrane of a neuron, lasting approximately one thousandth of a second and able to travel down the axon to its ends, where it triggers the release of neurotransmitters.

amblyopia:
A disorder in which one or both eyes loses the ability to see details; sometimes referred to (along with another disorder, strabismus) as
lazy eye
.

amygdala:
An almond-shaped structure under the rostral pole of the temporal lobe that is involved in basic positive and negative emotional responses, including fear.

anterior cingulate:
The frontal part of the cingulate cortex, which surrounds the corpus callosum in a collarlike shape.

attachment:
A strong and persistent desire to be close to a familiar caregiver, especially when the child is stressed or upset.

axon:
A long, thin structure that emerges from a neuron, and which is specialized for the long-distance transmission of information by transmitting action potentials along its length toward its ends, where synapses reside.

basal ganglia:
As part of the forebrain, a group of nuclei (clusters of neurons) located underneath the neocortex and involved in directing choices, attention, and rewards. The name is an exception to the principle that ganglia are defined as being found outside the brain.

brainstem:
An evolutionarily old part of the brain that sits between the spinal cord and forebrain and controls basic functions that usually do not reach conscious awareness, such as breathing.

Broca’s area:
A part of the left hemisphere of the neocortex, discovered by Pierre Paul Broca, that is essential in the production and comprehension of language.

cerebellum:
A brain component occupying about one seventh of the brain in most mammals, and which integrates sensory information to drive perceptions, movement, and higher functions.

cerebral cortex:
See
neocortex
.

circadian rhythm:
A cycle of brain and body activities that takes approximately one day, and which can proceed without day-night light cues.

cognitive:
Relating to higher brain functions such as thinking, regulation of emotional responses, and declarative learning and memory.

congenital:
Inherited by genetic mechanisms.

corpus callosum:
The principal route for communication between the hemispheres of the neocortex; composed entirely of axons.

corticotropin-releasing hormone (CRH):
A peptide released by the hypothalamus in response to stress, and which in turn activates the pituitary gland.

cortisol:
A steroid hormone secreted by the adrenal gland. Cortisol is the principal human stress hormone or glucocorticoid.

dandelion child:
A child who thrives in a wide variety of environments. Based on Swedish folk wisdom (
maskrosbarn
).

dendrite:
A treelike structure, extending from the cell body of a neuron, that receives communicating synaptic inputs from other neurons.

dopamine:
A neurotransmitter that regulates reward, attention, and action, and which is secreted by neurons in the substantia nigra and the nucleus accumbens, two small structures in the brain’s core.

dopamine uptake blocker:
A chemical, such as methylphenidate (Ritalin), cocaine, or methamphetamine, that prevents dopamine from being taken back up into neurons after it has been released, thereby prolonging dopamine’s action.

dorsal:
In the brain, the direction toward the top of the head; in the spinal cord, toward the back. The opposite of ventral.

effect size:
The difference between groups divided by the variability of one or both groups. For Cohen’s d' as described in
chapter 8
, d' = 0.2–0.3 is considered small, d' = 0.5 is considered moderate, and d' = 0.8 or larger is considered large. A moderate effect size would be likely to be noticeable in an individual in everyday life.

epigenetic:
Having to do with inherited change that comes from mechanisms other than the DNA sequence itself. Here in particular, a long-lasting chemical modification to DNA that affects gene expression.

epinephrine
(also known as
adrenaline
)
:
A chemical signal from the sympathetic nervous system that activates fight and flight responses, and which is released from the adrenal glands.

executive function:
A suite of related abilities for self-control that includes planning ahead, inhibiting undesirable responses, and holding information in working memory.

fMRI (functional magnetic resonance imaging):
A noninvasive imaging method that uses the properties of oxygenated hemoglobin in blood to visualize where blood flow has increased in response to neural activity.

frontal lobe:
A major part of the neocortex, located toward the front and containing a variety of smaller regions.

fusiform face area:
A part of the visual system that is active in recognition of faces and other familiar objects.

gene:
A sequence of DNA that encodes the sequence of a protein, as well as containing markers that specify under what conditions the protein will be made.

gestational age:
The number of weeks since a pregnant woman’s last menstrual period, approximately two weeks more than the number of weeks since conception.

glial cell:
A cell of the nervous system that is not a neuron and that supports brain function. Plural,
glia
.

glucocorticoid:
A class of steroid hormones involved in suppressing the immune response and secreted by the adrenal glands.

glutamate:
The most widespread neurotransmitter of the brain, used by a neuron to increase the likelihood of other neurons firing. Also an amino acid, one of twenty used to make proteins and peptides.

gonadotropin-releasing hormone:
A peptide molecule, secreted by neurons of the hypothalamus, that activates secretion of gonadotropin by the pituitary gland.

gray matter:
The type of brain tissue in which neurons, dendrites, and synapses are found; like white matter, it can contain axons, blood vessels, and glia.

gyrus:
A single fold of the neocortex, consisting of a part of the gray matter sheet folded on itself and containing a bit of white matter in its core. Plural,
gyri
.

hippocampus:
A brain region central to learning, memory, spatial navigation, and regulation of emotional response.

hypothalamic-pituitary-adrenocortical (HPA) system:
A complex set of interacting systems—including the hypothalamus, pituitary gland, and adrenal glands—that regulate stress responses.

hypothalamus:
A brain region located beneath the thalamus with a central role in controlling many core functions, including emotional responses, stress, hunger, thirst, and sexual behavior.

insula
(also known as
insular cortex
)
:
A portion of the neocortex deeply buried inside a sulcus between the temporal and frontal lobe; important in the processing of emotions and in the body’s current state.

locus coeruleus:
A small brain region that secretes norepinephrine and sends axons throughout the brain.

longitudinal study:
A study in which the same people are followed over time, so that individual changes in function can be measured. As opposed to a cross-sectional study, in which people in different groups are compared with one another.

medial:
The direction toward the body axis midline. The opposite of lateral.

melanopsin:
A pigmented protein found in certain cells of the retina and involved in converting light into signals to the brain to drive the circadian rhythm.

meta-analysis:
A statistical technique in which multiple studies are pooled to increase confidence in the overall conclusion and to detect biases in individual studies.

monoamine oxidase:
An enzyme with multiple functions, including the breakdown of the neurotransmitters dopamine, serotonin, melatonin, epinephrine, and norepinephrine.

motherese:
The distinctive speech instinctively used to speak to infants.

motor:
Relating to movement.

mutation:
An error in the copying of a gene.

myelin:
A fatty sheath, generated by some glial cells, that wraps around axons to provide electrical insulation, thereby speeding signals.