Early Childhood Education
Development, Brain
The brain develops dramatically and rapidly during the period of early childhood (Schore, 2001). At birth the child’s brain weighs less than a pound, and triples in weight by the second birthday (Bloom, Nelson, and Lazaroff, 2001). Growth and development in brain structures and functions are reflected in rapid changes in the child’s physical, mental, and emotional capacities. Developmental changes in brain structure and function influence and are influenced by the child’s experiences and environment, and have dramatic implications for caregiving and education practice during early childhood (see Gallagher, 2005). Recent advances in knowledge about early brain development, including structural and functional aspects of brain development, have implications for early childhood care and education.
Overview: Brain Structure and Function
Described as “plastic” due to its ability to adapt and change, the brain manages, regulates, and responds to information from the body and from the environment. Before birth, the brain develops in orderly stages, beginning with the neural tube, which connects the spinal cord to the base of the brain, the brain stem, in the first four weeks of gestation. As this process is completed, the brain divides into three distinct sections: the forebrain, midbrain, and hindbrain. The forebrain divides into specialized sections: such as the cerebral cortex, the frontal cortex, and the prefrontal cortex. The brain develops in structure (regions of the brain consisting of clusters of brain cells called neurons) and function (activities of the brain, such as sending electronic signals or hormone production and secretion). Structures important to early development and learning include neurons, the cerebral cortex, prefrontal cortex, and the amygdala. Functions include synaptogenesis, myelination, and cortisol production of the HPA (hypothalamic- pituitary-adrenal) system. These structures and functions demonstrate some ways the brain develops in early childhood, and are detailed below.
Neural Development
Neurons are the basic building blocks of the nervous system. Most of the human brain’s 100 billion neurons are in place before birth. Through the use of electrical signals, neurons communicate messages within the brain and to and from parts of the body (Kolb and Whishaw, 2001). Information travels between neurons in an orderly fashion, from the dendrites (where electrical impulses are received) to the axon (where impulses are conducted away from the cell body). When information reaches the axon, it travels across a small gap, called a synapse, to another neuron. The synapse is the point of communication between two cells (Shonkoff and Phillips, 2000). Synapses rapidly grow more numerous and dense after birth, in a process known as synaptogenesis. A dense network of synapses facilitates transmission of more messages in the brain, affording better processing of cognitive, social, and emotional information.
In infancy, synaptogenesis produces more synapses than needed. Consequently, a one-year-old has approximately one and a half times more synapses than an adult (Bruer, 2004). Though scientists are uncertain why the brain overproduces synaptic connections, it is possible that it is nature’s way of preparing children’s brains for a variety of possible environmental and social experiences (Shonkoff and Phillips, 2000). Unused or seldom-used neurons slow their synapse production, in a process known as pruning. With pruning, neurons remain intact, but unused synapses are eliminated.
Children need a variety of sensory experiences to help neural material develop. When children are deprived of sensory stimulation, they may exhibit developmental delays and disabilities. Certain developmental tasks appear to have sensitive periods, or stages at which exposure to certain experiences is essential to developing certain skills. Probably because the brain is highly plastic, there are not many known sensitive periods for humans. Some aspects of language may not develop properly when a child is not exposed to sufficient language before puberty. Research with animals suggests that complex, stimulating environments improve synapse density and structure, but there is not sufficient evidence that complex or stimulating environments increase neural synapse material in humans.
During myelination a white, fatty tissue, called myelin, grows around the nerve axons. Myelin protects the nerves, speeds the transmission of electric signals, and prevents signals from firing haphazardly. Many areas in the brain are myelinated in early childhood, but some, such as the frontal cortex (responsible for complex thinking, problem-solving, and regulation) develop later in childhood. Slower signal transmission of neural signals, caused by unmyelinated neurons, is associated with less regulated, disorganized behavior in younger children. Early malnutrition, in particular, insufficient fat intake, is associated with poor myelination (Shonkoff and Phillips, 2000); therefore, quality nutrition is important for optimal brain development.
Cortex Development
The cerebral cortex is the brain’s outer layer and is responsible for conscious activity. It has two sides, or hemispheres, which have specialized functions. The right side of the cerebral cortex specializes in processing negative and intense emotions, nonverbal and spatial processing, and creativity (Kolb and Whishaw, 2001). The left side of the cerebral cortex specializes in positive emotions, language development, and interest in new objects and experiences. These brain specializations are highly plastic: they change easily. When an individual has brain damage to one side of the brain, the undamaged area takes over the damaged side’s functions (Kolb and Whishaw, 2001). An important consideration for early childhood concerning hemispheric specialization is that the sides of the cerebral cortex develop at different rates. The right side of the cerebral cortex grows more quickly during the first 18 months of life and dominates brain functioning for a child’s first three years. This difference in brain hemisphere growth rate emphasizes the role of negative and intense emotion and creativity in a child’s very early development.
The frontal lobes of the cerebral cortex are important for emotional development. The frontal lobes of the cortex allow the person to inhibit and control the experience and expression of emotion. The development of the cortex during the early years assists a child in developing self-regulation. At the very front of the frontal lobes, the prefrontal cortex is responsible for executive function, the processes of self-regulation, planning, and organization of behavior (Shonkoff and Phillips, 2000). Executive function is also closely related to, but not the same as, attention and working memory. The prefrontal cortex doesn’t independently regulate children’s behavior, but it works in concert with other structures of the brain and develops dramatically during early childhood (Schore, 2001).
The Amygdala
Self-regulation in children is dependent on two very closely interconnected areas of the brain, the prefrontal cortex and the amygdala. The amygdala, a small, almond-shaped structure, is believed to be the structure in the brain most connected to emotional and fearful reactions (Blair, 2002). It is interconnected with many areas of the brain, including the prefrontal cortex and neural pathways for vision. It is highly receptive and reactive in nature and is sensitive to environmental stimulation. The location of the amygdala, deep in the center of the brain, has made it difficult to study, but it is accepted that the emotional (amygdala) and executive function (prefrontal cortex) structures of the brain work cooperatively to facilitate self-regulation.
Stress System Development: HP A and Cortisol
One of the most important functions of the brain is to help the individual recognize and respond to danger and stress. The HPA (hypothalamic-pituitary- adrenocortical) system produces the hormone cortisol. Cortisol fluxuates in response to stress, and contributes to the “fight or flight” reflex that helps the body respond to challenging situations (Kolb and Whishaw, 2001). People have a baseline cortisol level that is typical for their own biology and temperament. Cortisol fluctuates throughout the day (usually higher in the morning and lower in the afternoon) and increases in response to stress. In moderate doses cortisol is a good thing—it helps the brain respond to stress and solve problems. But too much cortisol production over a long period of time leads to problems with memory, self-regulation, and anxiety (Gunnar and Cheatham, 2003).
The HPA system and cortisol levels respond to social interactions and are believed to be connected to the child’s developing attachment system. From animal research, we know that nurturing parenting is important to the offspring’s developing HPA system. When mother rats groom their pups frequently, their pups have more stable cortisol levels and react less to stress. When caregivers are sensitive and responsive children have fewer increases in cortisol and are less reactive to stress. Children’s cortisol increases when separated from their caregivers, and when experiencing transitions. Children who experience extreme adverse conditions develop patterns of stress reactivity that includes increased cortisol levels, slow growth, cognitive deficits, and behavior problems. However, there is evidence that these patterns can be reversed when the quality of care improves (Gunnar and Cheatham, 2003).
The following are the major implications for caregiving and education:
• Neural synapses develop rapidly in early childhood, and prune when unused. Children benefit cognitively, emotionally, and physically from many, varied sensory experiences. More importantly, sensory deprivation can lead to cognitive and emotional problems for children.
• The right hemisphere of the cerebral cortex, which experiences and manages intense, negative emotion, is dominant in early childhood. Children benefit from interactions with sensitive, responsive adults who help them to manage strong, negative emotions. These caring relationships are particularly important in the early years.
• Myelination is important for healthy transmission of neural messages. Children benefit from nutrition that balances protein, carbohydrates, and fat. Fat intake should not be severely restricted in young children.
• The HPA (cortisol) system develops patterns in response to intensity and duration of stress the child experiences. Frequent and intense stress in early childhood is associated with cognitive and emotional problems in childhood and into adulthood. Warm, sensitive caregiving is associated with lower cortisol levels and healthier growth, social and emotional development. Children need protection from some stressors, such as violence and abuse, and benefit from interaction with caring adults who provide support and help the child cope with stressful situations. Early childhood is an important time for learning to establish productive social relationships.
Conclusions
Advances in technology have facilitated increased understanding of brain development in early childhood. As technology continues to develop, information about the brain’s structures and functions will provide more insight to children’s development. Some key concepts of brain development are supported by research.
The brain is plastic, and changes and adapts in response to experience. Adverse experiences have a lasting effect, but can sometimes be remediated by intervention. Some adverse experiences, such as exposure to toxins, abuse, and malnutrition, are difficult to overcome. Therefore, it is most important to protect children from harmful experiences, and assure that children receive proper nutrition, health care, and sufficient sensory stimulation (Shonkoff and Phillips, 2000).
When children have birth defects or disabilities that prevent them from obtaining quality experiences in typical environments, intense and early intervention is necessary to assure that the child has sufficient experiences to compensate for difficulties. Children with sensory impairments, such as vision or hearing impairments, need access to high-quality early intervention. There is substantial evidence that early and intense intervention is effective in remediating some developmental problems for children with disabilities (Shonkoff and Phillips, 2000).
Early relationships are an influential aspect of children’s healthy brain development. When caregivers are sensitive and responsive to young children’s needs, and provide adequate sensory stimulation, children develop competence in social, emotional, cognitive, and physical abilities. Evidence for this early connection between quality caregiving and relationships is substantiated by research on right hemispheric specialization and dominance (Schore, 2001) and HPA (stress) system development (Gunnar and Cheatham, 2003). Finally, research on brain development provides information about supporting children’s development of self-regulation. The neural mechanisms for children’s regulation develop through childhood and adult support is essential until those neurological mechanisms (i.e., myelination) are in place. Adults help children manage intense, negative emotions and support language development for children expressing their needs. See also Disabilities, Young Children with.
Further Readings: Blair, Clancy (2002). School readiness: Integrating cognition and emotion in a neurobiological conceptualization of children’s functioning at school entry. American Psychologist 57(2), 111-127; Bloom, Floyd E., Charles A. Nelson, and Arlyne Lazerson (2001). Brain, mind, and behavior, 3rd ed. New York: Worth; Bruer, John T. (2004). The brain and child development: Time for some critical thinking. In Edward Zigler and Sally J. Styfco, eds. The Head Start debates. Baltimore: Brookes, pp. 423-434; Gallagher, Kathleen Cranley (2005). Brain research and early childhood development: A Primer for DAP. Young Children 60(4), 112-120; Gunnar, Megan R., and Carol L. Cheatham (2003). Brain and behavior interfaces: Stress and the developing brain. Infant Mental Health Journal 24(3), 195-211; Kolb, Bryan, and Ian Q. Whishaw (2001). An introduction to brain and behavior. New York: Worth; Schore, Allan N. (2001). Effects of a secure attachment relationship on right brain development, affect regulation, and infant mental health. Infant Mental Health Journal 22(1-2), 7-66; Shonkoff, Jack P., and Deborah A. Phillips, eds. (2000). From neurons to neighborhoods: The science of early childhood development. Washington, DC: National Academy Press.
Web Sites: Brain Facts: A Primer on the Brain and Nervous System. Free download of this 55p document from Society of Neuroscience. Available online athttp://www.sfn.org/baw/pdf/brainfacts.pdf; The Brain from Top to Bottom. Available online at http://www.thebrain.mcgill.ca/flash/pop/pop_plan/plan_d.html; Educarer: Early brain development: What parents and caregivers need to know—contains interactive illustrations of brain and neuron. Available online at http://www.educarer.com/brain.htm; PBS: The secret life of the brain—Excellent resource on brain development from infancy to adulthood, including a 3-D tour of the brain. Available online at http://www.pbs.org/wnet/brain/; Zero to Three Brainwonders. Available online athttp://www.zerotothree.org/brainwonders/.
Kathleen Cranley Gallagher and Maria Pelzer Bundy