attention, and emotional processing during the school-age years.
Finally, the limbic system is located deep inside the brain, behind the cortex. Two important components of the limbic system are the amygdala and hippocampus. The amygdala aids in our understanding and expression of emotions, especially negative feelings, such as fear and rage. The hippocampus also plays a role in emotional processing, especially the formation of emotion-laden memories (Image 2.6).
4. Higher-order regions may not mature until adulthood.
The cerebral cortex is the outermost shell of the brain. It is divided into four lobes. The occipital lobe, located near the back of the brain, is primarily responsible for visual processing. This brain region appears to undergo the most change from birth through age 2 years. In contrast, the volume of the parietal lobe (located on the sides and top of the brain) peaks around age 6. The parietal lobe is primarily responsible for integrating visual, auditory, and tactile information. The temporal lobe (located on the sides and bottom of the brain) also shows peak growth during the first 6 years of life. The temporal lobe has multiple functions, including hearing, language, and the expression and regulation of emotions.
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The volume of the frontal lobe peaks in late childhood or early adolescence. The frontal cortex plays an important role in language production, problem-solving, and memory—skills that develop rapidly during childhood. A particular region of the frontal lobe, the prefrontal cortex, shows peak growth in early adolescence and reorganization into early adulthood. This brain region is responsible for planning, organizing, and prioritizing activity to meet long-term goals. Development of the prefrontal cortex is believed to underlie young adults’ increased capacity for attention, inhibition, and overall self-regulation (de Haan & Johnson, 2016).
5. Experience can affect the brain.
Although it may seem that brain maturation determines development, the relationship between maturation and behavior is bidirectional. The brain can change in response to experience. Biological maturation and environmental experiences interact in three ways to shape the developing brain (Cicchetti, 2019).
First, certain aspects of brain development are gene driven. These aspects are largely impervious to the effects of experience and almost entirely determined by genetics. For example, the development of the brain stem and migration of neurons from the center of the brain to the cortex is believed to be genetically preprogrammed. Developmental psychologists sometimes refer to this importance of genes over experience in embryonic development as canalization (Blair, Raver, & Finegood, 2016).
Second, some aspects of brain development are experience expectant—that is, the formation of the brain region is partially dependent on information received from the environment. Infants have an overabundance of neural connections, many of which they do not need. Connections that are used are maintained and strengthened while connections that are not used atrophy and die. Whether a connection is maintained or pruned depends on experience. For example, an infant exposed to the Japanese language during the first few years of life may strengthen neural connections responsible for processing the sounds used in Japanese. However, infants not exposed to Japanese during this early period of development may lose neural connections that play a role in processing this language. Consequently, children who are not exposed to Japanese in infancy or early childhood may find it difficult to speak the language without an accent. Developmental psychologists often refer to periods of development in which experience can greatly shape neural structure and functioning as developmentally sensitive periods.
Third, brain development can be experience dependent—that is, environmental experiences in later life can lead to the formation of new neural connections or to changes in the brain’s organization or structure. Neural plasticity refers to the brain’s malleability, that is, its capacity to change its structure and/or functioning in response to environmental experiences. These experiences can be either internal or external. Internal experiences alter the immediate environment of the brain and nervous system. For example, exposure to too much testosterone or stress hormone can lead to structural changes in various brain regions. In contrast, external experiences come from outside the organism. For example, an infant exposed to environmental toxins can experience brain damage (Cicchetti, 2015).
Neuroscientists have discovered that the brain is remarkably adaptive to environmental stressors, especially when these stressors occur early in life. Perhaps the most striking example of brain plasticity is seen following a surgical procedure called a functional hemispherectomy. This surgery is performed on some children who have medically intractable epilepsy that arises in one hemisphere of the brain. These seizures cause severe impairment, occur very frequently, and are not responsive to medication. The surgeon removes the entire parietal lobe of the nonfunctional hemisphere (the origin of the seizures) and severs the corpus callosum, a bundle of neurons that allow the seizure to travel from one hemisphere to the other.
Despite removal or disconnection of several brain regions, children usually show remarkable recovery from the surgery. Children often experience weakness or mild paralysis on the opposite side of the body. Furthermore, if the left hemisphere is removed, most children experience problems with language. However, children usually recover much of this lost functioning within 6 to 12 months after surgery, as the remaining hemisphere gradually assumes many of these lost functions. In fact, most children who undergo this surgery are able to return to school 6 to 8 weeks later (van Schooneveld, Braun, van Rijen, van Nieuwenhuizen, & Jennekens-Schinkel, 2016).
Positive environmental experiences can also lead to the formation of new neural connections. Long ago, the neuropsychologist Donald Hebb (1949) proposed that the simultaneous activation of neurons can cause the neurons to form new connections. Hebb suggested “neurons that fire together, wire together.” Recently, neuroscientists have been able to show synaptogenesis, that is, the formation of new neural connections due to experience. For example, rats reared in enriched living environments (e.g., given extra space and access to toys and mazes) show differences in brain structure and functioning compared to rats reared in typical cages. Humans who receive extensive training in Braille show growth in brain regions responsible for processing the sense of touch. Even skilled musicians show a reorganization of brain regions responsible for controlling the finger positions of their instruments (Cicchetti, 2019).
Review
The brain consists of 100 billion neurons that form trillions of synaptic connections. Neurons relay information within themselves electrically; they communicate between one another using chemical messengers called neurotransmitters.
Brain development is characterized by rapid growth followed by periods of neuronal pruning. Development begins in evolutionarily older brain regions (e.g., brainstem, basal ganglia, limbic system) and ends in regions responsible for higher-order functions (e.g., the cerebral cortex).
Development can be gene driven, experience expectant, or experience dependent. Environmental experiences can lead to synaptogenesis and the reorganization of neuronal connections (i.e., plasticity).
2.3 Psychological Influences on Development
How Is Learning Theory Important to Understanding Childhood Disorders?
Psychologists often use learning theory to explain and predict children’s overt actions. From the perspective of learning theory, children’s behavior
