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Using psychology to inform genetics and vice versa:
Examples from neurodevelopmental disorders
Dorothy Bishop
Wellcome Trust Principal Research Fellow
University of Oxford
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Using psychology to inform genetics and vice versa: Examples from - - PowerPoint PPT Presentation
Using psychology to inform genetics and vice versa: Examples from - - PowerPoint PPT Presentation
Using psychology to inform genetics and vice versa: Examples from neurodevelopmental disorders Dorothy Bishop Wellcome Trust Principal Research Fellow University of Oxford 1 Neurodevelopmental disorders of unknown origin Specific Language
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Neurodevelopmental disorders of unknown origin
Specific Language Impairment
♦ Language does not follow normal
developmental course – immature speech sounds/grammar
♦ No obvious explanation (e.g.
hearing loss, physical abnormality, acquired brain damage)
♦ Normal development in other areas
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http://news.bbc.co.uk/1/hi/education/2638889.stm Thursday, 9 January, 2003, 11:15 GMT
Daily grunt parents hold children back
Not enough talking going on
Parents who do little more than grunt at their children every day are damaging their language development, a literacy expert has said. Alan Wells, director of the Basic Skills Agency, says parents no longer talk to their children and instead just let them sit in front of the television or computer for hours.
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Dizygotic/Fraternal (DZ twins): share 50% of polymorphic genes Question: Is concordance for disorder higher in identical than in fraternal twins?
Twin Study Method
Monozygotic (MZ) twins: genetically identical
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handic
Identical twins Fraternal twins
Specific language impairment Low language History of therapy Low IQ Unaffected
Status of co-twins of children diagnosed with specific language impairment
Bishop, D. V. M., North, T., & Donlan, C. (1995). Genetic basis of specific language impairment: evidence from a twin study. Developmental Medicine and Child Neurology, 37, 56-71.
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Conclude……..
- Substantial genetic influence on SLI
- But traditional definition of disorder does not
“carve nature at its joints”
- Need for better specification of phenotype –
use theoretically informed measures
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Some promising component skills
- Auditory processing skills
- Phonological short-term memory
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One promising candidate skill:
Auditory temporal processing
Stimuli: 75 ms tones, high and low frequencies Child learns to press button 1 for high tone, and button 2 for low tone Then responds to tone sequences, varying in
- Rate of presentation
- Length of sequence
Bishop, D. V. M., et al 1999. Different origin of auditory and phonological processing problems in children with language impairment: evidence from a twin study, Journal of Speech, Language and Hearing Research 42: 155-168.
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Children’s Nonword Repetition Test
Child listens to spoken nonwords and repeats, e.g. 2 syllables: hampent 3 syllables: dopelate 4 syllables: confrantually 5 syllables: pristoractional
Gathercole, S. E., Willis, C., Baddeley, A. D., & Emslie, H. (1994). The children's test of nonword repetition: a test of phonological working memory. Memory, 2, 103-127.
Another promising candidate skill:
Phonological short-term memory
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DeFries-Fulker (DF) analysis
z-score
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Fraternal Identical Co-twin Co-twin Proband Proband genes only shared environment only nonshared environment only
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Auditory Repetition Test: DF analysis
0.5 0.0
- 0.5
- 1.0
- 1.5
2.0
z-score proband proband co-twin co-twin
- 2..
Fraternal Identical
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Nonword Repetition Test: DF analysis
0.5 0.0
- 0.5
- 1.0
- 1.5
- 2.0
- 2.5
z-score proband proband co-twin co-twin
- 2..
Fraternal Identical
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Conclusions from twin studies
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Auditory deficit phonological STM deficit Environmental factors Morphosyntax deficit phonological STM deficit Genetic risk Phonological STM deficit
Twins resemble each other regardless of whether MZ
- r DZ
MZ twins more similar to each
- ther than DZ
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The bottom line
- Traditional diagnostic categories do not
identify aetiologically distinct conditions
- We will get more coherent results from
molecular genetic studies if we first use behaviour genetics to identify heritable phenotypes
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