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asperger's syndrome information and features

         

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Genetics

Copying Nerves
Underconnectivity
Brain Structure / Foetal Development

Immunization / MMR

Other Ideas

Genetics

There is research that shows evidence of links between autism and a number of genes.

Studies of families and twins also suggest there is a genetic component.

  • Identical twins - 63-98% chance of BOTH having autism.

  • Non-Identical Twins - 0-10% chance of BOTH having autism.

  • Ordinary siblings - 0-3% chance of BOTH having autism.

The Autism Research Centre at Cambridge University is currently asking for volunteers to take part in such studies.

There is little doubt that autism is at least in part genetic, but the big question is which genes and why.

Copying Nerves

A study at the University of California found that abnormal activity in neurons that help individuals imitate others may underlie some of the social deficits found in autism.

The autistic children studied had less brain activation in an area involved in understanding others' state of mind (the inferior frontal gyrus pars opercularis) when asked to imitate and observe facial expressions. The degree of activation of the 'mirror neurons' housed in this area correlated with measures of social impairment. The lower the activation, the stronger the impairment the children had.

There was also reduced activity in the insula and the amygdala, areas of the brain that deal with emotions.

The researchers believe that children with autism use other parts of the brain to perform the task that they tested. For example, using visual and motor clues without experiencing the internally felt emotional significance of the imitated facial expression.

Underconnectivity

Researchers at Carnegie Mellon University and the University of Pittsburgh using functional magnetic resonance imaging (fMRI) scans have found numerous abnormalities in the activity of brains of people with normal IQs who have autism. Their findings indicated a deficiency in the coordination among brain areas.

Underconnectivity theory explains why some people with autism might have normal or even superior skills in some areas, while many other types of thinking are disordered.

In the study participants read and indicated their comprehension of English sentences. In both the control brains and in the brains with autism, language functions were carried out by a similar network of brain areas, but in the autism brains the network was less synchronized, and an integrating centre in the network, Broca's area, was much less active. However, another centre, Wernicke's area, which does the processing of individual words, was more active in the autism brains.

It has been suggested that the brain compensates for this lack of interconnectivity by developing more independent, free-standing abilities in each brain centre.

Research by the University of London has also found that people with autistic spectrum disorders have less brain activity when looking at faces than most people. This is because the face processing areas of the brain are not well connected to those parts of the brain that control attention. Most people would pay more attention to a face than they would a picture of just an object, but people on the autistic spectrum find this much harder to do and it doesn't have the same effect on us.

Brain Structure / Foetal Development

The Cambridge Research Centre has a theory that autism is caused by exposure to higher than normal levels of testosterone in the womb, resulting in the brains of male or female foetuses developing as they usually would in a male to more extreme degree than normal. This would include earlier brain growth, less hemispheric connectivity, and an abnormally large amygdala. They feel this is also evidenced by autistic people being stronger systemisers and weaker empathisers than most, characteristics which are generally considered to be more male than female.

Other researchers have found characteristic abnormalities in various parts of the brain that are associated with autism such as a smaller than normal cerebellum and abnormally small and few cerebellar neurons, which may be caused by interrupted brain development in the foetus.

Immunization / MMR

Some researchers have hypothesized that measles vaccinations may trigger an abnormal immune response that causes autism, and many parents believe with absolute certainty that the MMR (measles, mumps and rubella) vaccine has been responsible for causing their child's autism. However, no research has ever proved a link, and the overwhelming majority of experts believe the vaccine is safe and essential for maintaining public health.

Despite this, rates of MMR vaccination in England have continued to fall as parents opt to have separate vaccinations at private or mobile clinics, some of which are unregistered and whose safety and effectiveness are questionable.

Strong evidence that there is no link has come from a recent study that looked at the incidence of autism in a Japanese city before and after the withdrawal of the MMR jab in 1993 and found that autism rates kept rising even after the withdrawal of MMR.

Rates of autism diagnosis have been rising over the last decade, but this is most likely due to the official expansion of the diagnostic criteria to include Asperger's Syndrome in the early 90’s coupled with increased awareness among the medical establishment and the public.

It is worth remembering that autism is not a fatal disease. On the other hand the consequences of measles, mumps and rubella can be fatal, and the less children are vaccinated against them the more the risk of an epidemic goes up.

Other Ideas

Immune System

Researchers at Johns Hopkins University have found certain immune system components that promote inflammation are consistently activated in people with autism, and suggest that brain inflammation may be the cause of autism. Anther study found raised levels of nitric oxide (a chemical involved in immune response which is known to affect neurodevelopmental processes) in the plasma of children with autism.

Brain Damage

Damage to the brain, such as through being deprived of oxygen for a length of time during birth has been considered as a cause of autism. A Danish study showed that children with autism were more likely than most to have had birth complications, but as the majority still hadn't, this could not be a cause in itself, but may be a possible contributing factor.

Serotonin

Other researchers suspect that autism may somehow be related to serotonin dysfunction. Serotonin is a neurochemical in the brain that modulates mood and pain. Low levels of serotonin are associated with clinical depression, anxiety disorders, and sensitivity to light.

Allergies

Some people believe that autistic people suffer from allergies to various substances, mainly foods, and the treatment of these allergies combined with the removal of the offending foods can in turn reduce what are believed to have been behavioural symptoms of autism. However, it would also be entirely possible for the allergies themselves not to be the cause of autism at all but merely a common characteristic of it.

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