From Birth to Two: the Neuroscience of Infant Development

Photo courtesy of AAAS

Photo courtesy of AAAS

“There are many misconceptions about child development,” said Pat Levitt, Provost Professor at the Keck School of Medicine, University of Southern California at the latest Neuroscience and Society lecture convened by the Dana Foundation and American Association for the Advancement of Science (AAAS). Some of the most prevalent myths include that humans are born with a blank slate; children are sponges; 80% of development takes place by 3 years old; and that a child’s outcome is predominantly self-determined. Moreover, many consider the mixture of fate, free will, parenting, genes, and environment a mysterious “black box” that ultimately decides a child’s success.

However, science has demonstrated that brains are built bottom-up, and both genes and experiences contribute significant impacts on early development. During the first several years of life, the brain grows rapidly; 700 synapses are formed per second in the infant brain (but the number of neurons is set at birth). In fact, children’s brains create 40% more nerve connections than necessary, so as they reach adolescence, the brain undergoes a process called “pruning,” which eliminates superfluous connections.

While genes provide a blueprint for development, Levitt emphasized the importance of experience in shaping the developing brain. The recognition that toxic stress—a result of prolonged anxiety and/or neglect—on an infant’s brain can have lifelong consequences has been a “sea change in the field,” said Levitt. He showed several images of the brains of rats exposed to different environments during development, which demonstrated visible physiological impacts. Additionally, experience and environment can affect the genome (epigenetics). Yet if early experiences—both positive and negative—are so impactful, why don’t we retain memories of them? Levitt explained that these experiences affect the architecture of the brain, thus “tuning the system” adversely before long-term memory develops.

Aided by a series of adorable videos, Lisa Shulman, associate professor of pediatrics at the Albert Einstein College of Medicine, described key infant developmental milestones and how to know if something “goes wrong.”

Parallel to Levitt’s explanation of bottom-up brain development, she noted that skills build upon one another. As we are social animals, infants are preprogrammed for a particular sensitivity to human faces and interaction. They look at faces more than any other pattern or shape, show a preference for the human voice, and imitate facial expressions.

Some of the first motor milestones include: head control by 4 months, ability to sit by 9 months, and walking by 18 months. Experience and temperament impact how quickly a baby’s development advances. Therefore, they require a certain degree of freedom to explore and learn.

When it comes to language, many parents think their child will begin “talking out of the blue.”  But, communication grows over time, along with increased social awareness. There are a number of behaviors that demonstrate the progression of communication: by 2 months infants should smile and vocalize; by 5-9 months, imitate facial expressions and respond to their names; and by 9-12 months, usually say their first words.

What happens when an infant misses these milestones, such as not responding to one’s name by 9 months, not pointing by 14 months, or not forming words by 9 months? Shulman said that developmental delays can signal a variety of issues. For example, why might an infant respond to sounds but not his own name? Why might an infant be able to walk down but not up a staircase? The former could be a sign of an autism spectrum disorder; the latter a sign of muscular weakness. Shulman emphasized that the period from birth to 3 is a crucial window to address issues because the brain is at its highest level of neuroplasticity or malleability.

Lisa Freund of the National Institute of Child Health and Human Development (NIHCD) gave insight into the research priorities of NIH’s extramural research program on infant development. Key areas include newborn screening and diagnosis; brain development; parenting; language acquisition; communication; early predictors of autism spectrum disorders; and treatment of physical and psychological trauma (toxic stress).

Technologies such as neuroimaging and eye tracking are enabling researchers to better understand the infant brain, said Freund. She described how researchers are adapting the Lifespan Human Connectome Project, which studies differences across the human lifespan, for infants (the youngest age group in the project is currently 4-6 years old). She directed the audience to the Institute’s website, which has many valuable resources, especially for parents.

Next time you’re on the train or bus, take a look at the infants or toddlers around you. More likely than not, they will be transfixed on a handheld device. An audience member asked about the implications of these devices for early development. According to Shulman and Freund, handheld electronic devices are more problematic when a child is using them in isolation and not engaging with others; however, using the device with an adult can mitigate negative impacts because human interaction is maintained. Nevertheless, the American Academy of Pediatrics recommends limiting infant usage of handheld devices.

With the growing body of information and guidance about infant development, how should parents determine an appropriate level of interaction and attention? Will parents who want their children to be overachievers overdo these techniques? The speakers said that it’s vital for infants to have shared interactions and not be neglected. Some parents may need to be taught how to do this. While there is no scientific consensus on what amount of interaction is adequate, Levitt said that the quality of interaction can often be more important than quantity.

– Josh Ettinger, program assistant, AAAS Scientific Responsibility, Human Rights and Law Program

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