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Behavioural phenotypes (Y1) - Coggle Diagram
Behavioural phenotypes (Y1)
Nature v Nurture
Nature (innatists / nativists) - nature is the primary factor that influences physical, psychological and behavioural characteristics that we develop - all aspects of our development are biologically determined by genetic inheritance
DNA profile
Genetic risk factors
Characteristic examples -
Height, eye colour, hair colour, skin colour, genetic diseases and risk for heart disease
Genetic basis for everyday disease - twin studies:
many common physical disorders have a clear genetic basis to them e.g. cancer, osteoarthritis, back pain and cataracts
Certain psychological conditions have a high degree of heritability e.g. eating disorders, anxiety and depression
Many behavioural and psychological traits are also extremely heritable e.g. hyperactivity, impulsivity, some autistic traits
There is a role for genes and biology in the development of likelihood of experiencing some of these challenges
Genetic syndromes - insight into the nature v nurture debate (known genetic cause)
If we know there is a genetic difference, we can look at the pathway from the genes through to protein development, to neurodevelopment to development and influence on behaviour
Genetic syndromes associated with intellectual disability -
Account for approximately 1/3 of all cases of intellectual disability (50% severe, 13% mild / moderate)
Individually, syndromes are rare but total numbers are high - estimates between 350,000 and 750,000 individuals in the UK with a genetic syndrome in 2008
Gene people UK:
registered charity aiming to improve the lives of those individuals with genetic conditions; 1 in 25 children now impacted, almost 2.4 million
Nurture (empiricists) - nurture has a major role, as we are born as blank slates and everything that happens to us in our life and environment shapes the way we develop
Early experiences of social interaction
Neglect and maltreatment
Exposure to toxins in the womb
Socioeconomic status
Diet and nutrition
Nurture characteristics -
Parenting style, personality, social attitudes, phobias, bilingualism, influence of a language-rich environment and prenatal alcohol
History of the debate
Victorian scientist Francis Galton coined the phrase of the debate
Believed that human intelligence was largely a matter of nature - good genes with a good genetic factor for intelligence leads to a high IQ
Know this is not the case - environment also has a significant role to play in intelligence and that there is an interaction between genetics and environments
Instigated the eugenics movements which focused around ideas of genetic determinism and selective breeding population based on only those who had these kinds of genetic factors determining high IQ, high success and attractiveness
-> Sterilisation of people with learning disabilities and those who were considered less successful / intelligent
Different ways of looking at the gene-brain-behaviour pathway
Genotype - genetic makeup; specific difference in the gene that we can identify faily precisely in individuals with those conditions
Phenotype - composite of observable characteristics - specific changes in the physical appearance / development influenced by the genotype
Behavioural phenotype - Nyhan (1972) - not simply associated physical characteristics but also behavioural / cognitive outcome associated with the genotype - relationship between genes and behaviour
From genes to behaviour
Total specificity - genetic syndromes have unique behavioural outcomes
A behavioural phenotype should consist of distinctive behaviour that occurs in almost every case of a genetic or chromosomal disorder, and rarely in other conditions (Flint and Yuke, 1994)
Very few examples of it -
-> Prader-Willi Syndrome - hyperphagia - no off switch of hunger, no feeling full
-> Lesch-Nyhan syndrome - finger and lip biting, specific self injury, some have teeth removed to limit this
-> Rett Syndrome - stereotypic hand washing / wringing
Partial specificity - several different genetic syndromes may lead to a single outcome - most commonly occurring effect of genetic syndromes:
Heightened probability or likelihood that people with a given syndrome will exhibit certain behavioural and developmental sequelae relative to those without the syndrome
E.g. different disorders share a behavioural outcome
Strengths and differences across genetic syndrome groups and domains of behaviour and development -
Within a particular area of behaviour, each group performs differently
Age range of participants 4-54, measuring different moods and challenges
A - sign indicates that they perform worse than other groups, and a + sign indicates better performance - an O signals no difference
More repetitive behaviour in Fragile X syndrome for example (++++) than in Prader Willi (--)
Genetic difference is influencing behavioural responses in a different way
Every single group has a different behavioural presentation, and there may be some areas of overlap but each condition is distinct
The behavioural phenotype from the genetic mutations = identification of each condition
https://docs.google.com/document/d/1dFnLdHFIh5ViRj6F1wHv71td_5hs-XLGQP7qz7fWuiw/edit
Within-Syndrome Differences
Prader-Willi Syndrome
1:10,000, 1:15,000 - chromosome 15 - same as autism, but different genes (q11-q13)
Paternal deletion in 70% of cases, maternal uni parental disomy (duplication - 25%) and imprinting abnormality (2.5%)
Symptoms -
Intellectual disability
Deficits in inhibition
Repetitive behaviour
physical phenotype
Hyperphagia
Temper outbursts
Nature - genetic difference (Thompson et al, 2002) -
Same condition but slightly different mutation of the same gene = difference in presentation of behaviour, indicating a strong influence of the gene
Genetic difference - Veltman et al (2004) -
Deletion group vs UPD (2 maternal copies) group
-> Matched on chronological age and sex
-> No group difference on core diagnostic features
UPD participants compared to deletion group
-> Worse in - daily living skills, decreased puzzle skills
-> Higher in - autism prevalence, motor control, walking earlier, impaired social reciprocity
Same condition, same gene but difference in mutation leads to different outcomes in behaviour and development
Fragile X Syndrome
1:4,000-1:6,000 - X chromosome; FMR1 gene, CGG repeat expansion - moderate to severe intellectual disability, autism characteristics, averted eye gaze and repetivite behaviour as genetic code repeats on X chromosome
The effect of this has been shown to be different in different individuals:
Complete loss of function and protein production (complete silencing)
Over expression of protein (incomplete silencing)
Nature of protein production - Baker et al, 2019
Those with incomplete silencing (overexpression of protein) compared to complete silencing - autistic features increase, but intellectual functioning decreases
Same condition and same genetic change but differences in terms of the impact that gene has on protein function - effect visible on behaviour / development
Nature - Summary: it is clear that nature has a strong role to play in the development of behaviour and this is evidenced through behavioural phenotypes associated with genetic syndromes
Even within specific syndrome groups, the type of mutation and the biological consequences of the mutation has a differential effect on behavioural outcome
Problems with a nature aetiology-based approach
diagnostic overshadowing - tendency to attribute all problems to a primary diagnosis by layering other co-occuring conditions
Therapuetic nihilism - nothing can be done
Reflection of eugenics era
Diagnostic assessment demonstrated for example that an individual meets the criteria for another disorder and the transfer request that follows for a more appropriate environments; however, often missed when a syndrome has partial specificity of behavioural phenotypes (Moss and Howlin, 2009)
-> Boy with down syndrome has a typical autism profile, behaviour interpreted as stubborn, naughty or difficult
-> Stereotype perception due to Down Syndrome, and lack of recognition of his autistic characteristics because not known as co-occurring
Contemporary eugenices - Ridley, 1999 - genetic screening is laiisez-faire eugenics:
People make reproductive decisions to avoid genetic syndromes (pg.298)
Eugenics happen every day, and the most common victims are embryos with an extra 21 chromosome, who would be born with down syndrome
Nurture
Social deprivation - Sonuga-Barke et al, 2018 - Rutter ERA 1998 study:
Longitudinal study into the development of children adopted into UK families from Romania in the early 1990s
165 Romanian and 52 UK adoptees and their adoptive families recruited in the years following entry to the UK
R < 6 months = 67, R > 6 months = 98, UK adoption = 53
Immediate impact -
autism spectrum, disorder - cognitive impairment higher in the Romanian group adopted after 6 months, with the UK and younger than 6 months group performing similarly
-> Emotional problems (parent-reported) - also more prevalent in the adopted after 6 months group , better than the former but worse than UK
Disinhibiited social engagement - inattention and overactivity highest in the adopted after 6 months group, similar in other two
-> Emotional problems self reported - after 6 months group higher than the other two which were similar
Long term impact -
emotional problems, performed similarly but after 6 months group still higher - same trend in parents and self report
Conduct problems - similar levels from 6-15 years old in all three groups, with adopted after 6 months doing slightly worse, but similar levels in both
R > 6 months group more likely to have mmultiple difficulties / diagnosis:
Autism, social engagement, cognitive impairment, inattention and hyperactivity, conduct problems
Participants exposed to social deprivation for longer more likely to show -
Autistic traits, inattention and hyperactivity, cognitive deficits (some recovery), deficits in social engagement
Emotional and conduct problems in adolescence, more likely to have multiple difficulties
Nurture - Child Maltreatment (CM) - population based sample of 9 year old twins n = 8,192
CM defined as one or more types of maltreatment, either emotional abuse / neglect, physical or sexual
Neurodevelopmental conditions significantly higher in maltreated individuals (24%) than non-maltreated individuals (5%)
The risk for neurodevelopmental conditions was seven times higher in children exposed to maltreatment vs those not exposed to maltreatment
Alternative interpretations - genetics influence both the development of NDCs and exposure to CM and neglect:
Genetic factors may influence likelihood of certain psychological conditions / mental health conditions that may then be related to difficulties in looking after a child
Genie - NDC from early on that led to being neglected, or was it the consequence of early deprivation that led to difficulties in developing language and communication
Are there common genetic factors that increase risk of exposure rather than this being a true assessment of nature v nurture
Contemporary views of the debate: we cannot say it is nature v nurture
We can say the difference in behaviour between two individuals could be nature or nurture (genetic or environmental)
The environment can affect our behaviour not only through processes of learning but also in influencing the way our genes are functioning in our development - interaction
Genotype + environment -> process of development -> behaviour
Both information from the genotype and from the environment combine and interact to determine the course of behavioural development
Epigenetics
Emerging area that shows how environmental influences, or children's experiences, affect the expression of their genes
Genes are therefore not set in stone - it is nearly always nature and nurture
During development, the DNA that makes up our genes accumulates chemical marks that determine how much or how little of the gene is expressed
Collection of chemical marks is the epigenome - different experiences children have rearrange chemical marks, explaining why genetically identical twins can exhibit different behaviours, skills, health and achievement
In twins reared apart but MZ:
can sometimes have very different upbringings
Overlapping tendencies of behaviour in some scenarios such as social interaction and emotional regulation
Challenges are different due to environments
Nature and nurture interact
Example of epigenetics - environment impacted how genes are expressed
Gene x environment interactions
Lesch-Nyhan Syndrome - social interaction helps behavioural phenotype of SIB
One of the very few syndromes with total specificity of phenotype behaviour - genetic difference leads to specific compulsive self injurious behaviour (SIB)
Onset of SIB is sudden and violent rather than a gradual emergence
Compulsive self injury, commonly biting, requiring restraint, drastic measures such as teeth removal or teeth guards
High levels of career concern
SIB different across conditions, with high/low levels of social interaction
When there is no social interaction, SIB is higher - in social situations with lots of attention, rate of SIB is often lower
Influence of the environment even in LNS syndrome with total specificity of a phenotype you would expect to be wholly genetic
Prevalence of SIB in genetic syndromes rom different studies - almost 100% of people with LNS display SIB, with little variability
Much more variability in other groups, depending on the measure used
It was always considered that people have little control over their behaviour, reinforcing the nature view
Cornelia de Lange Syndrome (CdLS) - treating GERD pain helps lower SIB
1:40,000 - deletions on chromosomes 5, 10 and X - main features of:
mild-profound intellectual disability
Small stature
Upper limb abnormalities
Distinctive facial features
High prevalence of gastroesophageal reflux (90%)
Limited speech, receptive-expressive language discrepancy
Increased prevalence of autistic like behaviours, particularly repetitive behaviours
Painful health problems in CdLS: discomfort underlies SIB, Luzzani et al, 2007
GERD - muscle at top of stomach not strong enough to contain the contents of stomach, which leads to a burning sensation and can cause tissue damage - in serious cases, ear infection, mouth and teeth issues due to acid in the stomach
Individuals with GERD - hyperactivity, poor sleep, teeth grinding and self-injurious behaviour
Improvements in all these behavioural signs following GERD treatment
Pain as a setting event but environmental influence remains present:
Not treated for pain - boy with CdLS, picking and scratching around the chest, SIB stable across different environments
Treated pain - girl picks and scratches, but SIB is variable across different environments
Conclusion - nature and nurture -
Evidence suggests a strong genetic influence on the occurrence and presentation of neurodevelopmental disorders - twin studies, population-based studies, cross syndrome comparisons, within syndrome comparisons
The assumption of a direct gene-behaviour link is over simplistic - environmental influences cannot be ignored, and gene x environment interactions are a more accurate depiction of combined influences
Evidence - Lesch-Nyhan syndrome and Cornelia de Lange syndrome
Importance of aetiology of intellectual development - people's social attitudes towards a syndrome name impacts the inclusion of these people within society
Aetiology about the conditions can help us as a society create a more accessible lifestyle for those with neurodevelopmental conditions
Behavioural phenotypes - behaviours are shown more frequently in individuals with a particular genetic syndrome than in individuals without the syndrome (Dykens et al, 2000)
When a behaviour onlycomes from one genotype, it is a total specificty behavioural phenotype
Partial specificity - comes from a few different genotypes - behavioural phenotypes associated with other genetic syndromes
Endophenotype - unobservable characteristics shown more freeuntly in individuals with the genotype than by individuals without the genotype and these include cognitibe, emotional and mtivational characteristics
Genetic expression gives way to physical, physiological and neuronal development - can affect patterns of cognitive and emotional/motivational processing - bidirectional relationship
This then leads to a framework in which a genotype can give rise to physical neuronal, cognitive, emotional/motivational and behavioural differences
Number of interactions can emerge which produce behaviour as a result
Also opportunity for multiple levels of intervention to help individuals with genetic conditions
Angelman syndrome - excessive smiling - example of motivational / emotional phenotype
Lowe Syndrome - sensory impairments which cause behavioural, same with gastrointestinal reflux issues in Lesch-Nyhan Syndrome and SIB
Cognitive phenotypes - Prader-Willi and Fragile X - attentional difficulties
Situations in the environment trigger these specific genotype behavioural phenotypes - as a result, the two have a significant interaction
Contexts of genetic behaviours are important