What are some environmental influences that impact brain development? • Drugs (tobacco, alcohol, prescription or illegal drugs) • Mother’s age • Radiation, toxic wastes and pollutants • Parasite (toxoplasmosis) • Stress
Drugs • Mothers who take large amounts of barbiturates may have babies who are addicted or may exhibit tremors, restlessness and irritability. • Alcohol (Heavy drinking) – Fetal alcohol syndrome is a cluster of abnormalities that appear in the offspring of mothers who drink alcohol heavily during pregnancy
Mother’sage • Down Syndrome, a form of mental retardation, is related to the mother's age • By age 40, the probability is slightly over 1 in 100. By age 50, it is almost 1 in 10. The risk is also higher before age 18.
Down syndrome • In most cases, Down syndrome occurs when there is an extra copy of chromosome 21. • The extra chromosome causes problems with the way the body and brain develop. • Down syndrome is the most common single cause of human birth defects • Symptoms include: • Impulsive behaviour • Poor judgment • Short attention span • Slow learning • Intellectual disability • Aggression
Radiation, toxic wastes and pollutants • Among the dangerous pollutants and wastes are carbon monoxide, mercury and lead. • Chromosomal abnormalities are higher among the children whose mothers were exposed to high levels of radiation • During the period of 25 weeks post conception, the central nervous system (CNS) is particularly sensitive to radiation. • The sensitivity is highest 8-15 weeks post conception • May result in a decrease of IQ or in a high probability of severe mental retardation.
Toxoplasmosis • Toxoplasmosis is an infection caused by the parasite Toxoplasmagondii. • You can get it by eating undercooked, infected meat, or handling soil or cat feces that contain the parasite. • Infants who become infected during pregnancy are said to have “congenital toxoplasmosis” infection • Infected babies have problems with: brain, eyes, heart, kidneys, blood, liver, or spleen. • Long term effects may include seizures, mental retardation, cerebral palsy, deafness, and blindness
Are there times during pregnancy when the effect of environmental factors is especially important?
Stress • Stress, neglect and ill-treatment in childhood could cause: • a serious and permanent deficit in language acquisition • Impaired personality development • Impaired intellectual and social skills
What is a genetic disorder? • A genetic disorder is a disease caused by a different form of a gene, called a variation, or a change in a gene, called a mutation • Inherited disorders - a mutated gene or group of genes is passed down through a family • Many people with genetic brain disorders fail to produce enough of certain proteins that influence brain development and function. • These brain disorders can cause serious problems that affect the nervous system.
How are genetic disorders inherited? • By obtaining genes from parents • There are three common types or modes of inheritance: dominant, recessive and X-linked (or sex-linked) • Dominant inheritance occurs when one parent has a dominant, disease-causing gene which causes abnormalities even if coupled with a healthy gene from the other parent (each child has a 50% chance of inheriting the disease-causing gene). • Recessive inheritance occurs when both parents carry a disease-causing gene but outwardly show no signs of disease
Each child has a 25% chance of inheriting both disease genes and being affected; 25% chance of inheriting two healthy genes and not being affected, and a 50% chance of being a carrier of the disorder • X-linked or sex-linked inheritance affects genes located on the X chromosome • If a mother has a female child, the child has a 50% chance to inherit the disease gene and be a carrier and pass the disease gene on to her children.
Tuberoussclerosis • Rare genetic disease that causes noncancerous tumours to grow in the brain and other organs. • Other Symptoms: • Developmental delays • Mental retardation • Seizures • Social-communicational problems (poor eye-contact, repetitive and ritualistic behaviours and speech and language delay) • Disruptive behaviours (over activity, restlessness, impulsivity, aggressive outbursts, temper tantrums, and self-injurious behaviours) • Mood-related difficulties (depressed mood, anxiety, extreme shyness) • Sleep problems
Phenylketonuria • A condition in which a baby is born without the ability to properly break down an amino acid called phenylalanine (Phe) • Children with untreated PKU may appear normal at birth. • By age three to six months, they begin to lose interest in their surroundings. • By age one they are developmentally delayed and their skin has less pigmentation than someone without the condition. • If Phe is not restricted in the diet, those with PKU develop: • Seizures • Severe developmental delay • Autism
Galactosemia • Galactosemia is a disorder that affects how the body processes a simple sugar called galactose • The signs and symptoms of galactosemia result from an inability to use galactose to produce energy. • Symptoms: • Convulsions • Irritability • Lethargy • Delayed development • Speech difficulties • Intellectual disability
Wilson’s disease • Caused by a build-up of copper in the body • It first attacks the liver, the central nervous system, or both • Build-up of copper in the central nervous system may result in neurologic symptoms: • Problems with speech • Physical coordination • Tremors or uncontrolled movements • Muscle stiffness • Behavioural changes
What is a genetic testing? • Genetic testing involves examining your DNA - the chemical database that carries instructions for your body's functions. • Genetic testing can reveal changes or alterations in your genes that may cause illness or disease. • Although genetic testing can provide important information for diagnosing, treating and preventing illness, there are limitations. • For example, if you're a healthy person, a positive result from genetic testing doesn't always mean you will develop a disease. • In some situations, a negative result doesn't guarantee that you won't have a certain disorder.
Questions: • What is the difference between environmental and genetic influences on brain development? • Is it possible to prevent some of the brain diseases? • Is it possible to diagnose a brain disorder by just observing a child? Why? • What is the best way to diagnose a genetic disorder?