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Prefrontal cortex development in humans begins around the fourth prenatal week from the neural tube, which is an embryonic structure that eventually becomes the brain and spinal cord. The parts of the neural tube are the prosencephalon, mesencephalon, rhombencephalon and spinal cord. It is the prosencephalon that will develop into the forebrain, an area encompassing the cerebrum along with two limbic structures, the hypothalamus and thalamus.
Arising out of embryonic ectoderm, the neural tube forms, and the most anterior portion, the prosencephalon, divides to become the telencephalon and diencephalon. The diencephalon differentiates into the thalamus, hypothalamus and associated structures, and the telencephalon becomes the left and right brain hemispheres. Often referred to as the cerebral cortex, the cerebrum is divided into four lobes: frontal, parietal, temporal and occipital.
Specifically concerned with the frontal lobes, prefrontal cortex development continues into adulthood. This area occupies the largest cerebral region and is active in organization, planning, decision-making and behavior regulation. Damage to the prefrontal cortex results in an inability to control impulses and learn from experiences with reward and punishment. Reasoning according to hypothetical situations might not be affected. When dealing with actual events, though, function is impaired.
In children, prefrontal cortex development is not yet completely understood. What is known is that brain development during early childhood is particularly influenced by love, affection, nutrition and genetics. Childhood experiences can affect the way in which the brain connects or processes information. If a small child is exposed to affection, for example, he or she will be able to reciprocate that behavior to others. Young children who receive very little love or attention typically cannot display empathy or emotion because relevant connections will not develop.
Synaptic density increases with age, and it occurs as a result of trillions of neurological connections, commonly called "wiring." Neuronal firing creates a network that is permanently established with repetitive experiences. Connections no longer being used or relied upon are eliminated through a process called pruning, which starts around the age of 11 years.
Research using magnetic resonance imaging (MRI) indicates that prefrontal cortex development is completed last, after other areas of the brain have already matured. Brain studies show that growth begins in the back and moves forward to the frontal lobes. White myelinated fibers are not as abundant in adolescents; adults have more. Myelination improves conduction speed and requires less energy.
Changes occur within the cerebral cortex later in life. After about age 40, the amount of gray matter and white myelinated fibers start to decrease. Biochemical changes also cause conduction to be altered.
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