Special Education

Biological Causes of Developmental Disorders

Did you know that the human brain weighs only 3 pounds and is about the size of a large grapefruit? Other animals have different sized brains. A sperm whale’s brain weighs only 4 pounds (think about the whale’s size compared to the size of its brain), a dog’s brain weighs 72 grams, and a gorilla’s brain weighs about 1 pound. That means that compared to our size, humans have pretty large brains. Our brains are made mostly of water (78 percent), fat (10 percent), and protein (8 percent). A living brain is so soft that you could cut it with a butter knife.

Scientists divide the brain into four different sections which are called lobes. The lobes are responsible for many different things such as emotions, reasoning, hearing, vision, and more responsibilities. Read the chart below to learn lots of interesting facts about your brain lobes.

Frontal Lobe

The frontal lobe is found in the area around your forehead. It is concerned with emotions, reasoning, planning, movement, and parts of speech. It is also involved in purposeful acts such as creativity, judgment, problem solving, and planning.

Parietal Lobe

The parietal lobes are found behind the frontal lobes, above the temporal lobes, and at the top back of the brain. They are connected with the processing of nerve impulses related to the senses, such as touch, pain, taste, pressure, and temperature. They also have language functions.

Temporal Lobe
The temporal lobes are found on either side of the brain and just above the ears. The temporal lobes are responsible for hearing, memory, meaning, and language. They also play a role in emotion and learning. The temporal lobes are concerned with interpreting and processing auditory stimuli.

Occipital Lobe
The occipital lobe is found in the back of the brain. The occipital lobe is involved with the brain’s ability to recognize objects. It is responsible for our vision.


Cerebral dysfunction may be focal or global. Focal and global processes may also affect subcortical systems, altering arousal (eg, causing stupor or coma) or integration of thought (eg, causing delirium).

Focal dysfunction usually results from structural abnormalities (eg, tumors, stroke, trauma, malformations, gliosis, demyelination).

Global dysfunction is caused by toxic-metabolic disorders or sometimes by diffuse inflammation, vasculopathy, major trauma, or disseminated cancer; these disorders affect multiple dimensions of cerebral function.

Recovery: Recovery from brain injury depends in part on the plasticity (ability of an area of the brain to alter its function) of the remaining cerebrum, a capacity that varies from person to person and is affected by age and general health.
Plasticity is most prominent in the developing brain.

For example, if the dominant hemisphere language areas are severely damaged before age 8 yr, the opposite hemisphere can often assume near-normal language function. Although capacity for recovery from brain injury is considerable after the first decade of life, severe damage more often results in permanent deficits. Gross reorganization of brain function after injury in adults is uncommon, although plasticity remains operative in certain specific areas of the brain throughout life.

Cerebral dysfunction syndromes: Specific syndromes include agnosia, amnesia, aphasia, and apraxia. Psychiatric conditions (eg, depression, psychosis, anxiety disorders) sometimes include similar elements.


In general, diagnosis is clinical, often assisted by neuropsychologic testing. Diagnosis of the cause usually requires laboratory tests (blood and sometimes CSF analysis) and brain imaging, either structural (CT, MRI) or functional (PET, SPECT).



WHat We Should KNOW about OUR BRAIN

2. Teacher Jun Brainy Tests





Meningitis is inflammation of the protective membranes covering the brain and spinal cord, known collectively as the meninges. The inflammation may be caused by infection with viruses, bacteria, or other microorganisms, and less commonly by certain drugs.[2] Meningitis can be life-threatening because of the inflammation’s proximity to the brain and spinal cord; therefore the condition is classified as a medical emergency.

The most common symptoms of meningitis are headache and neck stiffness associated with fever, confusion or altered consciousness, vomiting, and an inability to tolerate light (photophobia) or loud noises (phonophobia). Sometimes, especially in small children, only nonspecific symptoms may be present, such as irritability and drowsiness. If a rash is present, it may indicate a particular cause of meningitis; for instance, meningitis caused by meningococcal bacteria may be accompanied by a characteristic rash.


A condition which is characterized by a protrusion of the meninges of the brain or spinal cord through a defect in the spinal cord.


Hydrocephalus, (pronounced /ˌhaɪdrɵˈsɛfələs/), also known as “water on the brain,” is a medical condition in which there is an abnormal accumulation of cerebrospinal fluid (CSF) in the ventricles, or cavities, of the brain. This may cause increased intracranial pressure inside the skull and progressive enlargement of the head, convulsion, and mental disability. Hydrocephalus can also cause death. The name derives from the Greek words ὑδρο- (hudro-) “water”, and κέφαλος (kephalos) “head”.


Cerebral palsy is the name given to a large group of motor (body movement) disorders that begin early in life and result from brain injuries that are non-progressive (do not worsen over time). Some children with cerebral palsy also have learning, vision, hearing and language disorders. Brain injuries that produce cerebral palsy can happen before, during or after birth. Although the specific brain injury causing cerebral palsy does not worsen, the movement problems produced by the injury can vary over time.
In most cases of cerebral palsy, the exact cause is unknown. Some possibilities include developmental abnormalities of the brain, brain injury to the fetus caused by low oxygen levels (asphyxia) or poor circulation, infection, and trauma. Injury and asphyxia during labor and delivery once were thought to be common reasons for cerebral palsy. However, some current research suggests that cerebral palsy is caused by problems that happen earlier in the pregnancy and then result in a difficult delivery.

There are four basic types of cerebral palsy:

* Spastic (stiff, difficult movement)
* Dyskinetic or athetoid (involuntary and uncontrolled movement)
* Ataxic (poor coordination and balance)
* Mixed (combination of these types)


Down Syndrome is a birth disorder in which the baby has an extra copy of chromosome 21. The chances of giving birth to a baby with Down Syndrome increase sharply with maternal age, particularly when the mother is over 35.

There are three main types:

* trisomy 21 (the most common type): there is an extra chromosome 21 in every cell
* translocation: an extra part of chromosome 21 is attached to another chromosome in every cell
* mosaicism: some cells have an extra chromosome 21 attached, while others are normal.

Babies with Down Syndrome have distinctive physical features, including a slightly flattened face, eyes slanting upwards, and slightly smaller ears, hands and feet. They usually have some degree of intellectual impairment, and may be developmentally delayed. They frequently have other health problems, such as hearing or vision disorders; hypothyroidism; or skeletal, intestinal or heart defects.

Motor Neurone Disease (also Amyotrophic Lateral Sclerosis)

* Motor Neurone Disease (MND) is the name given to a group of diseases in which the nerve cells (neurons) that control the muscles degenerate and die.
* MND is a slowly progressive disease in that it gets steadily worse over time.
* MND causes increasing disability due to muscular weakness, generally without mental impairment or incontinence.
* Early symptoms are mild and include muscle wasting, muscle weakness, fasciculations (muscle twitching), difficulty swallowing and with speech, muscle cramps and spasms.
* In some cases symptoms are widespread from the start but in most instances the disease starts in a localised fashion becoming more generalised as it progresses.
* There are different types of MND and symptoms vary from person to person. Patterns of weakness, the rate and pattern of progression and survival time are also variable.

Duchenne muscular dystrophy (DMD)

It is caused by a defect in a gene inherited on the X chromosome. Since males have only one X chromosome, DMD primarily affects boys. Women can carry the defective gene but usually will not show symptoms since they have a normal copy of the gene on their second X chromosome. In Duchenne muscular dystrophy, the defect in the dystrophin gene causes muscles to produce abnormally low levels of the dystrophin muscle protein so that the membranes around muscle cells become weak and tear easily, eventually leading to death of muscle fibres and replacement by scar tissue. DMD is the most common form of muscular dystrophy, occurring in one out of every 3,000 male newborns.


Dyslexia is a learning disability that affects approximately 10 per cent of the population. Despite having average or above average intelligence, people with dyslexia have difficulty in reading, and in other language-based tasks such as writing and spelling.

Dyslexia is believed to be a neurological disorder with a hereditary component, although no gene has yet been identified as causing the disorder. Brain imaging techniques show that people with dyslexia process phonological information (i.e. sound-based information) in a different area of the brain than non-dyslexics.

Attention Deficit Hyperactivity Disorder (ADHD)

Attention deficit hyperactivity disorder (ADHD) is a neurodevelopmental disorder (a problem related to brain development) that causes hyperactivity, impulsive behaviour, and attention problems. It interferes with a person’s ability to exercise age-appropriate control of their behaviour and/or their cognition.


Autism is classified as one of the pervasive developmental disorders of the brain. It is not a disease in the sense that it can’t be caught from someone else as infectious diseases are. People with classical autism show three types of symptoms: impaired social interaction, problems with verbal and nonverbal communication, and unusual or severely limited activities and interests.

Characteristics may include repetitive and ritualistic behaviours, hand flapping, spinning or running in circles, excessive fears, self-injury such as head banging or biting, aggression, insensitivity to pain, temper tantrums, and sleeping and eating disturbances. These symptoms can vary in severity. In addition, people with autism often have abnormal responses to sounds, touch, or other sensory stimulation.


Aphasia is a neurological disorder caused by damage to the portions of the brain that are responsible for language. For most people, these are parts of the left side (hemisphere) of the brain. Primary signs of the disorder include difficulty in expressing oneself when speaking, trouble understanding speech, and difficulty with reading and writing.

Aphasia is not a disease, but a symptom of brain damage. Aphasia usually occurs suddenly, often as the result of a stroke or head injury, but it may also develop slowly, as in the case of a brain tumour, infection, or dementia. The type and severity of language dysfunction depends on the precise location and extent of the damaged brain tissue.

Functions of Right and Left Side of the Brain

Functions of Right Side of Brain

So, when I gave my right brain vs left brain test, they said that I am predominantly right-brained. What did that mean? What are the characteristic right brain functions?

Controlling Function
It is said that the first right brain function is controlling the left side of the body. Right brained people generally tend to work more with their left hand and instinctively move their left foot forward first, while walking. But this may not always be true. Similarly, if you are left brained, you will tend to use the right side of your body more.

Feelings and Intuitions
Right-brained people prefer following their instinct or the ‘gut feeling’. They generally do not bother themselves with logical patterns and prefer relying on a ‘hunch’. This makes right-brained people think out-of-the-box more often, as they have the ability to think in an unconventional way. A left brained person on the other hand, tends to follow a rational, logical pattern, regardless of what he or she believes.

Holistic View
A right-brained personality will tend to view things in a holistic way, rather than paying attention to finer details. A right brained person has an ability to understand and appreciate the bigger picture, the larger meaning of things. A left-brained person would rather look into the finer details and analyze those.

Gesturing and Synthesizing
Another very common characteristic of right brained people is that they are not too good with words and tend to rely on gestures to emphasize their points. They do not communicate as well as left-brained people do. Left brained people tend to communicate fairly well and in a precise manner, and do not feel the need to gesture while talking.

Also, right-brained people are more perceptive in the sense that they tend to listen ‘how’ people say something rather than the exact words they say. This gives right-brained people a better understanding of situations as they can tell when people are concealing something. Left-brained people tend to stick with the facts and work with only what is said and not what is implied.

Another one of the very common right brain functions is that it is better at creating images. A right brained person will remember people and events based on a picture they have in their mind. They also make associations between unrelated pictures. Like suppose they think that someone they know looks like a horse. So when they see a horse they will think of the person and vice-versa! Right brained people tend to have a stronger visual memory than left brained people. They are also a lot more imaginative.

Organizational Skills
The right side of the brain is also notoriously known for its lack of organizational skills and in a way, this characteristic tends to rub off on right-brained people. They are also known to not be very good at spotting logical patterns between things or events.

Left Brain Characteristics

Individuals with left brain domination are considered to be relatively more intelligent than their right brain counterparts. Left brain characteristic traits include being analytical, sequential, logical, objective and rational. This helps the left brain people to get into the details of the subject, analyze it and come to a rational conclusion, as opposite to right brained people who just grasp the subject half heartedly as their attention always lingers on ‘how’ things are happening, instead of ‘what’ things are happening. This happens mainly because left brained people rely more on verbal aspect of the subject, while right brain rely more on the visual aspect. You can also read more on right brain characteristics.

Left Brain Functions

# As we mentioned earlier, the right side of our body is wired to the left brain, while the left side of our body is wired to the right brain. It means our right hand is commanded by the left part of our brain, while our left hand is commanded by the right side of the brain. A look into right handedness and left handedness would make things much more clear for you. Our eyes are no exceptions either, as our right eye is guided by the left brain and left eye by the right brain.

When it comes to left brain functions, facts rule. Words and language is given utmost importance by this part of the brain. Left brain excels in analytical subjects such as math and science. It plays a vital role in the human body mechanism of learning new things, owing to its brilliant ability to comprehend various subjects. Being sequential, right brain facilitates order perception with immense ease as well. One of the most important functions of left brain is forming strategies using analytical and logical skills.

People with left brain domination tend to use logic, whenever they intend to solve any problem in life. Being detail oriented does help them to a great deal, as these people get to the root of the issue before coming to a conclusion or decision. They tend to relate their past with the present, in order to ensure that present as a smooth sail. These people believe that knowing new things is always useful, and hence they thrive for knowledge. The reality based nature of people with left brain helps them in being practical in life. These people are hardly seen taking risks. They play safe, plan things and then execute them. Read more on facts on the human brain.




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