In the past few decades, our understanding of infants’ behavior and functioning in cognitive, linguistic, social, and motor domains of development has been enhanced by new techniques of brain research. Remarkable discoveries related to links between brain structure and function have informed our understanding of the role of the environments in which development takes place and vulnerability and resilience of human brain to environmental harm. In their landmark publication From Neurons to Neighborhoods, Shonkoff and Phillips (2000) describe development of human brain as highly dependent upon the child’s experiences. Brain development relies on certain forms of environmental exposure (i.e. light, sounds of speech, touch and other stimuli) to develop normally. Development of synapses (junctions that convert electrical impulses into chemical signals thus allowing nerve cells to communicate with each other) is genetically programmed to be experience-expectant. Infant’s development, therefore, is likely to be compromised in environments deprived of the expected external input, as it may lead to arrests of development in areas of the brain that depend on exposure. Infants’ brains are also experience-dependant, meaning they encode new experiences in the environment. Environmental factors vary for each individual; some experiences and exposures foster brain growth and refinement of existing brain structures, while others can be growth-inhibiting.

Importance of Early Brain Development Although formation of synapses can be found at different points of the human lifespan, prenatal and especially early postnatal brain development are characterized by the generation of trillions more synapses than at any later point in life. The peak synaptic density occurs during the first 3 years of life and largely coincides in time with the emergence of important skills, including early manifestations of working memory (see the article by Dawson, Ashman, & Carver, 2000). Windows of Opportunity vs. Plasticity of the Brain These findings have led some researchers to conclude that specific experiences must occur during certain windows of opportunity, during which absence of specific experiences puts children at risk for dysfunction (again, see Shonkoff & Phillips, 2000). Researchers have come up with different ways to describe these unique episodes in development: sensitive periods, during which particular experiences may most readily promote development, and critical periods, which are fixed times during which particular development must occur (for a review of these terms see Richard Lerner’s 2002 book Concepts and Theories of Human Development). Yet other researchers have questioned the evidence to support the critical period hypothesis and warned against the overenthusiastic use of the concept of sensitive period in design of interventions for children, reminding us that although there are periods during which organisms may be especially sensitive to environmental influences, we do not know if the consequences of growing up in deprived environments are irreversible. It is important to remember that development continues beyond infancy and that human development is characterized by plasticity. We should not assume that children who did not experience specific experiences at a certain period of time have no chance of developing positively. Importance of Caregiving Early care has a dramatic influence on the brain and neural systems. Click here to read more about the importance of infants’ interactions with their caregivers for maturation of the brain, stress response and affect regulation. Suggested online resources:

References:

  • Dawson, G, Ashman, S., & Carver, L. J. (2000). The role of early experience in shaping behavioral and brain development and its implications for social policy. Development and Psychopathology, 12, 695 - 712.
  • Lerner, R. M. (2002). Concepts and theories of human development (3rd ed.). Mahwah, NJ: Erlbaum.
  • Nelson, C.A. (2007). A neurobiological perspective on early human deprivation. Child Development Perspectives, 1(1), 13-18.
  • Shonkoff, J., & Phillips, D. A (Eds.). (2000). From neurons to neighborhoods. Washington, DC: National Academy of Sciences.

By Maryna Vashchenko