A long childhood feeds the hungry human brain

A five-year old’s brain is an energy monster. It uses twice as much glucose (the energy that fuels the brain) as that of a full-grown adult, a new study led by Northwestern University anthropologists has found.

The study helps to solve the long-standing mystery of why human children grow so slowly compared with our closest animal relatives.

It shows that energy funneled to the brain dominates the human body’s metabolism early in life and is likely the reason why humans grow at a pace more typical of a reptile than a mammal during childhood.

Results of the study will be published the week of Aug. 25 in the journal Proceedings of the National Academy of Sciences.

"Our findings suggest that our bodies can’t afford to grow faster during the toddler and childhood years because a huge quantity of resources is required to fuel the developing human brain," said Christopher Kuzawa, first author of the study and a professor of anthropology at Northwestern’s Weinberg College of Arts and Sciences. "As humans we have so much to learn, and that learning requires a complex and energy-hungry brain."

Kuzawa also is a faculty fellow at the Institute for Policy Research at Northwestern.

The study is the first to pool existing PET and MRI brain scan data — which measure glucose uptake and brain volume, respectively — to show that the ages when the brain gobbles the most resources are also the ages when body growth is slowest. At 4 years of age, when this “brain drain” is at its peak and body growth slows to its minimum, the brain burns through resources at a rate equivalent to 66 percent of what the entire body uses at rest.

The findings support a long-standing hypothesis in anthropology that children grow so slowly, and are dependent for so long, because the human body needs to shunt a huge fraction of its resources to the brain during childhood, leaving little to be devoted to body growth. It also helps explain some common observations that many parents may have.

"After a certain age it becomes difficult to guess a toddler or young child’s age by their size," Kuzawa said. "Instead you have to listen to their speech and watch their behavior. Our study suggests that this is no accident. Body growth grinds nearly to a halt at the ages when brain development is happening at a lightning pace, because the brain is sapping up the available resources."

It was previously believed that the brain’s resource burden on the body was largest at birth, when the size of the brain relative to the body is greatest. The researchers found instead that the brain maxes out its glucose use at age 5. At age 4 the brain consumes glucose at a rate comparable to 66 percent of the body’s resting metabolic rate (or more than 40 percent of the body’s total energy expenditure).

"The mid-childhood peak in brain costs has to do with the fact that synapses, connections in the brain, max out at this age, when we learn so many of the things we need to know to be successful humans," Kuzawa said.

"At its peak in childhood, the brain burns through two-thirds of the calories the entire body uses at rest, much more than other primate species," said William Leonard, co-author of the study. "To compensate for these heavy energy demands of our big brains, children grow more slowly and are less physically active during this age range. Our findings strongly suggest that humans evolved to grow slowly during this time in order to free up fuel for our expensive, busy childhood brains."

Connections in the brains of young children strengthen during sleep

While young children sleep, connections between the left and the right hemispheres of their brain strengthen, which may help brain functions mature, according to a new study by the University of Colorado Boulder.

The research team—led by Salome Kurth, a postdoctoral researcher, and Monique LeBourgeois, assistant professor in integrative physiology—used electroencephalograms, or EEGs, to measure the brain activity of eight sleeping children multiple times at the ages of 2, 3 and 5 years.

“Interestingly, during a night of sleep, connections weakened within hemispheres but strengthened between hemispheres,” Kurth said.

Scientists have known that the brain changes drastically during early childhood: New connections are formed, others are removed and a fatty layer called “myelin” forms around nerve fibers in the brain. The growth of myelin strengthens the connections by speeding up the transfer of information.

Maturation of nerve fibers leads to improvement in skills such as language, attention and impulse control. But it is still not clear what role sleep plays in the development of such brain connections.

In the new study, appearing online in the journal Brain Sciences, the researchers looked at differences in brain activity during sleep as the children got older and differences in brain activity of each child over a night’s sleep. They found that connections in the brain generally became stronger during sleep as the children aged. They also found that the strength of the connections between the left and right hemispheres increased by as much as 20 percent over a night’s sleep.

“There are strong indications that sleep and brain maturation are closely related, but at this time, it is not known how sleep leads to changes in brain structure,” Kurth said.

Future studies will be aimed at determining how sleep disruption during childhood may affect brain development and behavior.

“I believe inadequate sleep in childhood may affect the maturation of the brain related to the emergence of developmental or mood disorders,” Kurth said.

Cognitive scientists identify new mechanism at heart of early childhood learning and social behavior

Shifting the emphasis from gaze to hand, a study by Indiana University cognitive scientists provides compelling evidence for a new and possibly dominant way for social partners — in this case, 1-year-olds and their parents — to coordinate the process of joint attention, a key component of parent-child communication and early language learning.

Previous research involving joint visual attention between parents and toddlers has focused exclusively on the ability of each partner to follow the gaze of the other. In “Joint Attention Without Gaze Following: Human Infants and Their Parents Coordinate Visual Attention to Objects Through Eye-Hand Coordination,” published in the online journal PLOS ONE, the researchers demonstrate how hand-eye coordination is much more common, and the parent and toddler interact as equals, rather than one or the other taking the lead.

The findings open up new questions about language learning and the teaching of language. They could also have major implications for the treatment of children with early social-communication impairment, such as autism, where joint caregiver-child attention with respect to objects and events is a key issue.

"Currently, interventions consist of training children to look at the other’s face and gaze," said Chen Yu, associate professor in the Department of Psychological and Brain Sciences at IU Bloomington. "Now we know that typically developing children achieve joint attention with caregivers less through gaze following and more often through following the other’s hands. The daily lives of toddlers are filled with social contexts in which objects are handled, such as mealtime, toy play and getting dressed. In those contexts, it appears we need to look more at another’s hands to follow the other’s lead, not just gaze."

The new explanation solves some of the problems and inadequacies of the gaze-following theory. Gaze-following can be imprecise in the natural, cluttered environment outside the laboratory. It can be hard to tell precisely what someone is looking at when there are several objects together. It is easier and more precise to follow someone’s hands. In other situations, it may be more useful to follow the other’s gaze.

"Each of these pathways can be useful," Yu said. "A multi-pathway solution creates more options and gives us more robust solutions."

Researchers used innovative head-mounted eye-tracking technology that records the views of those wearing it, like Google Glass, and has never been used before with young children. Recording moment-to-moment high-density data of what both parent and child visually attend to as they play together in the lab, aresearchers also applied advanced data-mining techniques to discover fine-grained eye, head and hand movement patterns from the rich dataset they derived from multimodal digital data. The results reported are based on 17 parent-infant pairs. However, over the course of a few years, Yu and Smith have looked at more than 100 kids, and their data confirm their results.

"This really offers a new way to understand and teach joint attention skills," said co-author Linda Smith, Distinguished Professor in the Department of Psychological and Brain Sciences. Smith is well known for her pioneering research and theoretical work in the development of human cognition, particularly as it relates to children ages 1 to 3 acquiring their first language. "We know that although young children can follow eye gaze, it is not precise, cueing attention only generally to the left or right. Hand actions are spatially precise, so hand-following might actually teach more precise gaze-following."

A longitudinal study of grapheme-color synaesthesia in childhood

What colour is H? Is 4 brighter than 9? For most people these questions might seem baffling, but not for people with grapheme-color synesthesia.

In the first long-term childhood study on grapheme-color synesthesia, researchers followed 80 children to determine when and how associations between graphemes and colors develop. The latest results are published in the open-access journal Frontiers in Human Neuroscience.

Grapheme-color synesthesia is a harmless, alternative form of perception caused by subtle differences in the brain – possibly, stronger connections between centers for language and color – that give letters and numbers their phantom colors. It is passed down from parent to child in around 1 to 2% of the population.

In the present study, a group of synesthete children was tested three times between 6 and 10 years old. Each child was presented with 36 graphemes – the letters A to Z and digits 0 to 9 – and asked to choose the ‘best’ of 13 colors for each.

Children with grapheme-color synesthesia had already developed strong associations for around 30% of graphemes at 6 years old. At 7 years old, the same children had associations for around 50% of graphemes, and this increased to 70% of graphemes at 10 years old. The synesthete children were consistent in their choices over this 4-year period. Three children who were synesthetes at ages 6 to 7 were no longer so at 10 years old, indicating that the condition spontaneously disappears in some children as they grow older.

"This repeated testing of child synesthetes in real time allowed us to see for the first time that synesthetic colours emerge slowly during childhood, building up an incremental inventory of colorful letters and numbers," says Dr. Simner, a cognitive neuropsychologist who specializes in synesthesia, from the University of Edinburgh, UK.

The researchers’ next challenge is to determine how changes in the intensity of synesthesia - as strengthening or loss with increasing age - can be explained from changes in the organization of the brain.

(Image: Shutterstock)

Nurturing may protect kids from brain changes linked to poverty

Growing up in poverty can have long-lasting, negative consequences for a child. But for poor children raised by parents who lack nurturing skills, the effects may be particularly worrisome, according to a new study at Washington University School of Medicine in St. Louis.

Among children living in poverty, the researchers identified changes in the brain that can lead to lifelong problems like depression, learning difficulties and limitations in the ability to cope with stress. The study showed that the extent of those changes was influenced strongly by whether parents were nurturing.

The good news, according to the researchers, is that a nurturing home life may offset some of the negative changes in brain anatomy among poor children. And the findings suggest that teaching nurturing skills to parents — particularly those living in poverty — may provide a lifetime benefit for their children.

The study is published online Oct. 28 and will appear in the November issue of JAMA Pediatrics.

Using magnetic resonance imaging (MRI), the researchers found that poor children with parents who were not very nurturing were likely to have less gray and white matter in the brain. Gray matter is closely linked to intelligence, while white matter often is linked to the brain’s ability to transmit signals between various cells and structures.

The MRI scans also revealed that two key brain structures were smaller in children who were living in poverty: the amygdala, a key structure in emotional health, and the hippocampus, an area of the brain that is critical to learning and memory.

“We’ve known for many years from behavioral studies that exposure to poverty is one of the most powerful predictors of poor developmental outcomes for children,” said principal investigator Joan L. Luby, MD, a Washington University child psychiatrist at St. Louis Children’s Hospital. “A growing number of neuroscience and brain-imaging studies recently have shown that poverty also has a negative effect on brain development. 

“What’s new is that our research shows the effects of poverty on the developing brain, particularly in the hippocampus, are strongly influenced by parenting and life stresses that the children experience.”

Luby, a professor of psychiatry and director of the university’s Early Emotional Development Program, is in the midst of a long-term study of childhood depression. As part of the Preschool Depression Study, she has been following 305 healthy and depressed kids since they were in preschool. As the children have grown, they also have received MRI scans that track brain development.

“We actually stumbled upon this finding,” she said. “Initially, we thought we would have to control for the effects of poverty, but as we attempted to control for it, we realized that poverty was really driving some of the outcomes of interest, and that caused us to change our focus to poverty, which was not the initial aim of this study.”

In the new study, Luby’s team looked at scans from 145 children enrolled in the depression study. Some were depressed, others healthy, and others had been diagnosed with different psychiatric disorders such as ADHD (attention-deficit hyperactivity disorder). As she studied these children, Luby said it became clear that poverty and stressful life events, which often go hand in hand, were affecting brain development.

The researchers measured poverty using what’s called an income-to-needs ratio, which takes a family’s size and annual income into account. The current federal poverty level is $23,550 for a family of four.

Although the investigators found that poverty had a powerful impact on gray matter, white matter, hippocampal and amygdala volumes, they found that the main driver of changes among poor children in the volume of the hippocampus was not lack of money but the extent to which poor parents nurture their children. The hippocampus is a key brain region of interest in studying the risk for impairments.

Luby’s team rated nurturing using observations made by the researchers — who were unaware of characteristics such as income level or whether a child had a psychiatric diagnosis — when the children came to the clinic for an appointment. And on one of the clinic visits, the researchers rated parental nurturing using a test of the child’s impatience and of a parent’s patience with that child.

While waiting to see a health professional, a child was given a gift-wrapped package, and that child’s parent or caregiver was given paperwork to fill out. The child, meanwhile, was told that s/he could not open the package until the caregiver completed the paperwork, a task that researchers estimated would take about 10 minutes.

Luby’s team found that parents living in poverty appeared more stressed and less able to nurture their children during that exercise. In cases where poor parents were rated as good nurturers, the children were less likely to exhibit the same anatomical changes in the brain as poor children with less nurturing parents.

“Parents can be less emotionally responsive for a whole host of reasons,” Luby said. “They may work two jobs or regularly find themselves trying to scrounge together money for food. Perhaps they live in an unsafe environment. They may be facing many stresses, and some don’t have the capacity to invest in supportive parenting as much as parents who don’t have to live in the midst of those adverse circumstances.”

The researchers also found that poorer children were more likely to experience stressful life events, which can influence brain development. Anything from moving to a new house to changing schools to having parents who fight regularly to the death of a loved one is considered a stressful life event.

Luby believes this study could provide policymakers with at least a partial answer to the question of what it is about poverty that can be so detrimental to a child’s long-term developmental outcome. Because it appears that a nurturing parent or caregiver may prevent some of the changes in brain anatomy that this study identified, Luby said it is vital that society invest in public health prevention programs that target parental nurturing skills. She suggested that a key next step would be to determine if there are sensitive developmental periods when interventions with parents might have the most powerful impact.

“Children who experience positive caregiver support don’t necessarily experience the developmental, cognitive and emotional problems that can affect children who don’t receive as much nurturing, and that is tremendously important,” Luby said. “This study gives us a feasible, tangible target with the suggestion that early interventions that focus on parenting may provide a tremendous payoff.”

Irregular bed times curb young kids’ brain power

Given the importance of early childhood development on subsequent health, there may be knock-on effects across the life course, suggest the authors.

The authors looked at whether bedtimes in early childhood were related to brain power in more than 11,000 seven year olds, all of whom were part of the UK Millennium Cohort Study (MCS).

MCS is a nationally representative long term study of UK children born between September 2000 and January 2002, and the research drew on regular surveys and home visits made when the children were 3, 5, and 7, to find out about family routines, including bedtimes.

The authors wanted to know whether the time a child went to bed, and the consistency of bed-times, had any impact on intellectual performance, measured by validated test scores for reading, maths, and spatial awareness.

And they wanted to know if the effects were cumulative and/or whether any particular periods during early childhood were more critical than others.

Irregular bedtimes were most common at the age of 3, when around one in five children went to bed at varying times. By the age of 7, more than half the children went to bed regularly between 7.30 and 8.30 pm.

Children whose bedtimes were irregular or who went to bed after 9 pm came from more socially disadvantaged backgrounds, the findings showed.

When they were 7, girls who had irregular bedtimes had lower scores on all three aspects of intellect assessed, after taking account of other potentially influential factors, than children with regular bedtimes. But this was not the case in 7 year old boys.

Irregular bedtimes by the age of 5 were not associated with poorer brain power in girls or boys at the age of 7. But irregular bedtimes at 3 years of age were associated with lower scores in reading, maths, and spatial awareness in both boys and girls, suggesting that around the age of 3 could be a sensitive period for cognitive development.

The impact of irregular bedtimes seemed to be cumulative.

Girls who had never had regular bedtimes at ages 3, 5, and 7 had significantly lower reading, maths and spatial awareness scores than girls who had had consistent bedtimes. The impact was the same in boys, but for any two of the three time points.

The authors point out that irregular bedtimes could disrupt natural body rhythms and cause sleep deprivation, so undermining the plasticity of the brain and the ability to acquire and retain information.

"Sleep is the price we pay for plasticity on the prior day and the investment needed to allow learning fresh the next day," they write. And they add: "Early child development has profound influences on health and wellbeing across the life course. Therefore, reduced or disrupted sleep, especially if it occurs at key times in development, could have important impacts on health throughout life."

Bullying by childhood peers leaves a trace that can change the expression of a gene linked to mood

A recent study by a researcher at the Centre for Studies on Human Stress (CSHS) at the Hôpital Louis-H. Lafontaine and professor at the Université de Montréal suggests that bullying by peers changes the structure surrounding a gene involved in regulating mood, making victims more vulnerable to mental health problems as they age. The study published in the journal Psychological Medicine seeks to better understand the mechanisms that explain how difficult experiences disrupt our response to stressful situations. “Many people think that our genes are immutable; however this study suggests that environment, even the social environment, can affect their functioning. This is particularly the case for victimization experiences in childhood, which change not only our stress response but also the functioning of genes involved in mood regulation,” says Isabelle Ouellet-Morin, lead author of the study.

A previous study by Ouellet-Morin, conducted at the Institute of Psychiatry in London (UK), showed that bullied children secrete less cortisol—the stress hormone—but had more problems with social interaction and aggressive behaviour. The present study indicates that the reduction of cortisol, which occurs around the age of 12, is preceded two years earlier by a change in the structure surrounding a gene (SERT) that regulates serotonin, a neurotransmitter involved in mood regulation and depression.

To achieve these results, 28 pairs of identical twins with a mean age of 10 years were analyzed separately according to their experiences of bullying by peers: one twin had been bullied at school while the other had not. “Since they were identical twins living in the same conditions, changes in the chemical structure surrounding the gene cannot be explained by genetics or family environment. Our results suggest that victimization experiences are the source of these changes,” says Ouellet-Morin. According to the author, it would now be worthwhile to evaluate the possibility of reversing these psychological effects, in particular, through interventions at school and support for victims.

(Image: mentalhealthsupport.co.uk)

Brain Power: From Neurons to Networks is a 10-minute film and an accompanying TED Book. Based on new research on how to best nurture children’s brains from Harvard University’s Center on the Developing Child and University of Washington’s I-LABS, the film explores the parallels between a child’s brain development and the development of the global brain of Internet, offering insights into the best ways to shape both. The film and TEDBook launched at the California Academy of Sciences on November 8, 2012.

Scripps Florida Scientists Uncover Secrets of How Intellect and Behavior Emerge During Childhood

Scientists from the Florida campus of The Scripps Research Institute (TSRI) have shown that a single protein plays an oversized role in intellectual and behavioral development. The scientists found that mutations in a single gene, which is known to cause intellectual disability and increase the risk of developing autism spectrum disorder, severely disrupts the organization of developing brain circuits during early childhood. This study helps explain how genetic mutations can cause profound cognitive and behavioral problems.

The study was published in the November 9, 2012, issue of the journal Cell.

The genetic mutations that cause developmental disorders, such as intellectual disability and autism spectrum disorder, commonly affect synapses, the junctions between two nerve cells that are part of the brain’s complex electro-chemical signaling system. A substantial percentage of children with severe intellectual and behavioral impairments are believed to harbor single mutations in critical neurodevelopmental genes. Until this study, however, it was unclear precisely how pathogenic genetic mutations and synapse function were related to the failure to develop normal intellect.

“In this study, we did something no one else had done before,” said Gavin Rumbaugh, a TSRI associate professor who led the new research. “Using an animal model, we looked at a mutation known to cause intellectual disability and showed for the first time a causative link between abnormal synapse maturation during brain development and life-long cognitive disruptions commonly seen in adults with a neurodevelopmental disorder.”