Biological explanations of autism.

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What does the genetic explanation believe?
There are abnormalities in the genetic makeup and this can contribute to autism.
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What is the percent that a second child will have autism?
3-6% chance if the first child has autism.
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What is the chance of the general population developing autism?
0.06% chance of the general population developing autism.
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KEY QUESTION: What is concordance?
This is the percentage likelihood of one person having the disorder if a relative also has it.
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What did Folstein and Piven find out about concordance between siblings?
In 1991, they found a 3% concordance between siblings and approximately 4:1
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What did Folstein and Piven find out about monozygotic twins?
In 1991, he found a 96% concordance between monozygotic twins (MZ).
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What is the main limitation of the genetic explanation?
No one study has ever found 100% concordance therefore if autism was purely genetic then this figure should have been found. As a result nurture must play a part.
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KEY QUESTION: What is meant by the autism spectrum?
This is where there are different levels of impairment, not all people display the same symptoms with the same intensity.
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What is the difference between monozygotic and dizygotic twins?
Monozygotic twins are 100% genetically similar, whereas, dizygotic twins are 50% similar.
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Who conducted the key study for this explanation?
Rivito et al (1985)
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How many participants did he study?
23 sets of MZ twins and 17 sets of DZ twins, there was a 96% concordance with MZ twins and a 23% concordance for DZ twins.
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What is the problem with twin studies?
They are rare and so their sample size is small which means you can''t make generalisations. Also there was a high drop out rate.
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What is the problem with studies on MZ twins?
They are usually reared in the same environment, therefore the high concordance might be due to nurture rather than nature.
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Who identified the autistic gene?
Roder (2000) suggested that the HOSA1 gene may have a role in autism.
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Who identified the chromosomes that are abnormal in autistics?
Frith and Bailey, they both thought it was chromosome 7.
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What is the problem with the identification of an autistic gene?
It can lead to unethical mass screening and termination which is unethical.
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What did Bee find that suggests autism is genetic?
In 1989 Bee found that 10% of autistic children have chromosomal abnormalities known as the fragile X syndrome.
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What are the linkage between autism and other genetic disorders?
Autism, Tourettes and OCD are said to be similar because Comings and Comings (1991) found this.
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What was the conclusion of the genetic explanation of autism?
Carson et al (2000) concluded that if autism was entirely caused by genes then identical twins would have 100% concordance which suggests that autism is influenced by the environment; nurture.
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Name the second explanation of autism?
Neurological correlates.
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KEY QUESTION: Explain what is meant by the term neurological correlates?
Characteristic patterns of brain structure and function that are seen in people suffering from autism.
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What did Kalet find about endorphins?
In 1992, Kalet suggested that abnormal levels of endorphins in autistics might be responsible for autism as Leboyer (1992) found that injecting maltrexone reduced autistic symptoms-this blocks endorphins.
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What abnormalities have post mortem studies found?
The frontal lobe (planning and control), limbic system (emotional regulation) and brain stem and cerebellum (motor coordination).
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What is the advantage of a post mortem?
It is a physical observation of the brain.
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What is the problem of a post mortem?
It is impossible to establish cause and effect because abnormalities may be due to other injuries to the brain.
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What have PET scans found?
Zilboucious et al (2000) identified that 75% of autistics have abnormalities in the temporal cortex.
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What is the advantage of using a PET scan?
It is precise method of analysing the brain.
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What is the problem with a PET scan?
It is invasive because it is radioactive glucose.
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What have SPECT scans found?
Ohnishi (2000) used SPECT scans and found a positive correlation in the blood flow to the frontal cortex and impairment in communication and social interaction.
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What is the advantage of using a SPECT scan?
It is commonly with children because it involves less radiation.
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Who conducted the case study?
Allen in 2004.
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What was the aim of the case study?
It studies differences in the cerebellum activity between autistic and non-autistic participants.
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What did the study show?
Participants with autism had an increased activity in the cerebellum, compared to the controls of the cortex.
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What was the conclusion of Piviton's study?
In 1985, Piviton found that autistics have large brains in volume, the conclusion was that autistics have too many cell connections and so there are no direct links between the neurons and so less information is processed to the right area.
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What has neuroimagery led to?
Medical advancements in technology have allowed us to investigate the structure and function of the brain to identify medical causes and treatments for disorders.
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What is the conclusion of neurological correlates?
Frith (2003) suggested that at present, many of the finds are contradictory but as imaging techniques become more sophisticated, they are likely to advance our findings in the area.
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What is the percent that a second child will have autism?

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3-6% chance if the first child has autism.

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What is the chance of the general population developing autism?

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KEY QUESTION: What is concordance?

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What did Folstein and Piven find out about concordance between siblings?

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