Enviroment |
Enviroment and NeuroDevelopment |
| Enviroment and NeuroDevelopment - Enviroment effects in human brain and neurodevelopment. |
| NeuroDevelopmental effects in the brain and environmental factors. |
| What are NeuroDevelopmental effects? Impacts on the brain and nervous system which can affect physiological and cognitive development and can result in mental retardation, motor disabilities, behavioral disorders, learning impairment, delayed motor development, and sensory defects. |
| Why are we concerned? Damage to the brain or nervous system in utero or during childhood can result in life- Long disabilities. Exposures to some environmental toxins are known to cause permanent damage to a child's nervous system. |
| What causes these effects? Known or suspected causes of brain and nervous system disorders are exposure to chemicals and heavy metals including pesticides, lead, methylmercury, therapeutic drugs and food additives. Other chemical classes suspected of developmental neurotoxicity include antimitotics, polyhalogenated hydrocarbons, psychoactive drugs, solvents and vitamins. |
| How large is the problem? Four to eight percent of children born in the U.S. each year exhibit anatomical and/or functional deficits relating to brain and nervous system injury. An estimated one out of ten school-age children suffer from some type of functional deficit. |
| Who is at risk? the fetus, the infant and the child are especially vulnerable because their developing nervous system is more sensitive to toxins, such as lead and certain solvents and insecticides. Adults, with more developed nervous systems, are not as vulnerable to harm when exposed to many substances posing a risk to children. |
| How do we identify and study suspected neurotoxins and their risk to children? Animal model studies can be used to help predict human outcomes of exposure. The nature and extent of neurotoxic effects are often dependent on the timing of exposure. One of the periods when a human is most vulnerable to neurodvelopmental damage is organogenesis, the period in fetal development when many organ systems are formed. Organogenesis in the human is considered to occur from day 20 to day 55 of gestation; in comparison, organogenesis in the mouse is from day 7 to day 16. Thus, when studying the impacts of exposure to developing organs, the time and duration of exposure in the animal model must match the window of exposure for human development. Unfortunately, most studies designed to determine the effects of exposure to a chemical to humans are not conducted on pregnant or young animals, but on mature adults. For infants: To encourage eye movement and tracking, hold a rattle or any object that catches the baby’s attention about 8–12 inches from the baby’s face, wait for them to focus on it, then slowly move it from side to side. Their eyes should track the object’s movement. |
| Evidence that Social Environment Influences Brain Development |
| Environmental deprivation and/or stress can alter neuronal, hormonal, and immune systems. The alterations may impair normal development (or impair recovery from brain trauma) in a transient or long-term way. Environmental enrichment may increase neuronal complexity, improve brain function, and facilitate recovery from brain injury. |
| Cortisol reactivity to stress, hippocampus and immune changes (McEwen, Gunnar) |
| PET scan and behavior changes in Romanian orphans (Carlson & Earls) |
| Medical and behavioral development of preemies related to touch/massage (Field) |
| Dendritic complexity of rats in enriched environments (Diamond, Greenough) |
| Social behavior and brain changes in socially isolated monkeys (Harlow; Suomi) |
| Speculation about possible effects of child abuse and neglect (Perry; Teicher; Schore) |
| Environmental influences on specific abilities are more pronounced during sensitive periods |
| Axon growth and synapse formation in visual processing areas of kittens exposed to postnatal visual experience (Hubel & Wiesel) |
| Age differences in phoneme detection and language-learning (Kuhl, Stromswold) |
| Age differences in recovery from brain damage involve age at injury, age at testing, and type of test administered, sensitive and insensitive periods occur (Kolb) |
| Sensitive Periods |
| Brain growth and behavior of deafened songbirds (Marler) |