The development of the Down syndrome phenotype
Amanda Wood
In the first of these new features, Mandy summarises a discussion between the
Trust’s practitioners, which focused on a new research paper by Deborah Fidler
entitled ‘The emerging Down syndrome behavioural phenotype in early
childhood’
Wood A. The development of the Down syndrome phenotype. Down Syndrome News and Update. 2005;4(4);135-139.
doi:10.3104/updates.346
This month's practitioners meeting involved an interesting and fruitful
discussion of a new paper published in Infants and Children. The author, Deborah Fidler, of Colorado State University has been working in the field of genetic
syndromes associated with intellectual disabilities, including Down syndrome
since 1997.
This paper clearly and concisely reviews the growing body of research into the
already well-established concept of the behavioural phenotype associated with
Down syndrome.[1,2] However, the major focus of the paper is to examine the
profile from a developmental perspective, i.e. whether the so-called 'typical'
(and some might say 'inevitable') profile presented by the majority of
individuals in childhood and adolescence is already present and/or becoming
established in infancy. She frames this question within the context of early
intervention, highlighting the necessity of creating a curriculum and style of
delivery, which is grounded in scientific research evidence regarding children
with the specific diagnosis of Down syndrome and not a programme that simply
fits a wider target audience of children with developmental delay.
This review does not aim to describe the typical profile as Sue Buckley reviewed
this very clearly in her article 'Specificity in Down syndrome' in the last
issue.[4] Instead, the aim is to draw out the conclusions of Deborah's paper
with regard to the development across time of the phenotype and some of the
implications of this for early intervention and school support.
What is a 'phenotype'?
The term phenotype describes sets of observable traits, as determined by both
genetic makeup and environmental influences. Deborah explains that phenotypes
are 'probabilistic'.[pp.87] This means that people who have Down syndrome are
more likely to share one or more characteristic specific behaviours, as opposed
to those with a general developmental delay. Secondly, not every child with Down
syndrome will show all the behaviours and thirdly some of the behaviours
associated with Down syndrome may appear in other syndromes. Phenotypes are
purely descriptions of characteristics, which often appear together as a
syndrome. The phenotype does not explain why these traits appear together or how
they might interact.
Key points in Deborah's article
Research supports an emerging Down syndrome phenotype:
- Visual and social functioning and self help and daily living skills
are relative strengths
- Speech and language, verbal processing and motor functioning are
relative weaknesses
- Certain aspects of this phenotype are apparent in infancy although
the differences between the skills areas are much smaller than in older
children
- The discrepancies between skill areas may be magnified as the
children age and develop
- Intervention in infancy may be able to prevent or offset the
developmental trajectory associated with Down syndrome
- Intervention which is grounded in scientific research into the
phenotype and utilises the children's strengths is likely to be most
effective
The development of the phenotype
Deborah indicates that from her own research using the Mullen Scales of Early
Learning that a typical profile of "relative strengths in visual processing and
receptive language and relative weaknesses in gross motor skills and expressive
language skills" appears to be emerging by the age of 2. Further data from
parent reports showed the toddlers to have strengths in socialisation skills but
weaknesses in communication and motor skills.[p.94]
Interested readers are referred to her original paper to explore the specific
details of each domain of functioning as Deborah highlights many pieces of
research which show that sweeping generalisations about strengths and weakness
are not always useful as there are many subtle nuances within these areas, i.e.
when more specific skill areas are examined, one begins to see that not every
skill within a domain is always a strength or a weakness. For example, within
visuo-spatial processing (generally discussed as 'a strength'), although visual
imitation and visual memory skills do seem to be strengths, spatial and visuo-construction
skills appear to be relatively weaker.[p.88] There are also aspects of social
communication, which are weaker than others, e.g. non-verbal requesting (using
gestures like pointing to 'ask' for something) is a relative weakness whereas
social interaction and engagement skills are often seen as a strength.[pp.90-91]
Again, in the field of motor functioning, running and agility are actually
sometimes on a par with typical development whereas other motor skills such as
motor planning and certain precise movements of limbs and fingers are more
delayed.[pp.91-92]
Through the looking glass: Tiny variations and huge gulfs
Another very important point, which Deborah describes, is that although the
typical profile does appear to be present in an embryonic form during infancy,
the discrepancies between areas of strength and areas of weakness are much
smaller than they appear to be in older children. She suggests that these "tiny
variations" may become "magnified" as the children mature and "snowball" into
the distinct profile with which many readers will be familiar. The implication
is that certain interventions, at so-called sensitive periods during development
may help to "prevent or off-set" this process.[p.87]
The concept of critical and sensitive periods is a controversial one in the
research literature, not least due to the fact that the term 'critical' implies
that once a certain window of opportunity has passed, one can never acquire a
skill with the same degree of competency. However, it is likely that there may
be times when the brain is more receptive to certain types of learning. It is
likely that there is, for example, a sensitive period for learning grammar and
this is particularly salient for children with Down syndrome, for whom this
appears to be a particular area of weakness.[see 4 for more information] This
led the team to discuss the potential of early reading for developing children's
verbal short-term memory, syntactical knowledge and use of grammar in their
expressive language. We discussed the fact that those children who had started
reading activities early at the age of 2.5-3.5 years of age and had developed
extensive sight vocabularies may have made better progress with regard to the
effects on speech and language, particularly grammar development, than those who
started later. Interested readers are referred to Reading and writing
development for individuals with Down syndrome - An overview
[6] for a
discussion of these findings. This is, of course, not to say that targeted
intervention at any age is ineffective, as many adolescents and adults with Down
syndrome have demonstrated significant progress in a wide range of skill areas,
including literacy, later in life.[6] The old adage 'better late than never'
comes to mind even if 'it's never too late' is not always quite the case.
Nature and nurture
An extremely important point raised by this article, which must be highlighted
to every individual working or caring for a person with Down syndrome, is that a
diagnosis of Down syndrome in early infancy does not predict the future in any
certain way. Development is a dynamic process, whereby experiences within the
environment are key to the way in which the brain itself develops and is
organised.
The idea of a typical profile associated with Down syndrome is important to gain
a general understanding of which styles of intervention may be helpful however,
each individual with Down syndrome will only share the typical traits to a
greater or lesser extent, some may share characteristics of other syndromes,
some may have a full diagnosis of another syndrome, as Sue Buckley describes in
her article on dual diagnosis,
see p. 114 of this issue. As we shall see in the
section on implications, below, this point is crucial with regard to the ways in
which parents and professionals interact with the children as no single approach
will be equally effective for every individual with Down syndrome.
Early intervention
Above it was noted that intervention in infancy may help to prevent or offset
the emergence of some of the key weaknesses associated with Down syndrome in
childhood and beyond. However, Deborah indicates that this can only happen under
certain circumstances, possibly the most potent of these being the importance of
tailoring the intervention to the emergent profile of strengths and weaknesses
presented in infancy.[p.94]
Ideally, intervention should start as early as possible and should always
actively involve parents and children. Also, it is likely that parents who
understand the rationale behind different aspects of the intervention will be
more successful in their targeted work at home. Therefore, some degree of overt
training may be necessary as well as modeling practical activities and games to
the parents. The activities are likely to be most effective when they build on
the children's visual and social strengths and are tailored to the individual
likes and dislikes of the individual children. One way in which this idea can be
applied is by embedding opportunities to display skills which are likely to be
more difficult for the child (e.g. speech sound production or precise fine motor
movements) within tasks that will be perceived by the child as 'do-able' and
fun. For example, action songs or pretend play scenarios, which are often
extremely popular, could be used as a context in which to practice particular
speech sounds.
Also, it is important to collect information from families about activities,
toys, topics and so on which will be particularly motivating to each individual
child so that these can be incorporated into activities to target specific
skills and as reinforcers (rewards). One can begin to see from this discussion
that for early intervention for children with Down syndrome to be most
effective, a collaborative approach between practitioners and parents is
essential.
Personality and motivation
Deborah also draws the reader's attention to research on personality and
motivation, which indicates that many children with Down syndrome share certain
qualities, which manifest themselves in a characteristic style of social
interaction.[pp.92-93] Although the literature on temperament in infancy
suggests that infants with Down syndrome show the same distribution of
temperaments as typically developing infants, by childhood there seems to be a
tendency to show decreased task persistence and variable motivation during
work-related situations. Many children can be seen to utilise their strong
social skills to engage others in 'diversions' and collude with them in a
variety of behaviours unrelated to the learning task. She also cites research
that indicates that children with Down syndrome tend to make more efforts to
elicit help from adults than to persist with a task and develop their
independence and problem solving skills and a study, which suggests that
children with Down syndrome are less likely to repeat previous successful
outcomes.[p.93] These observations may be helpful in developing guidelines to
help those who support and particularly are involved with testing and assessment
of infants and children with Down syndrome.
However, it was noted above that children with Down syndrome show enormous
individual variation. As practitioners, an understanding of the behavioural
phenotype is extremely useful for those working with infants and children with
Down syndrome at one level, (e.g. curriculum planning) but on an individual
level, it is also crucial to take a step back from the profile and simply
observe the subtlety of the behaviours displayed by the child and the exact
situations in which they occur.
Conclusion
This paper provided an interesting starting for point for a discussion, which
helped us to reflect on our practice with children and families both in early
intervention and school liaison. It also provided ideas for future publishing
and training activities and inspired us to think about potential research
questions for the future.
We would encourage parents and practitioners to read the full article which has
in-depth discussion of issues relevant to early intervention for all aspects of
development and can be found at
http://depts.washington.edu/isei/iyc/fidler_18_2.pdf
The charity practitioner and research team look forward to sharing Deborah's work
with her further at the 4th International Conference on Developmental Issues in
Down Syndrome, to be held in Portsmouth, in the UK, in September, 2005. Please
see page 159 for more details of this forthcoming conference. The full programme
is also now available on our website, http://www.downsed.org
References
- Fidler, D.J. (2005). The emerging Down syndrome behavioural phenotype in
early childhood. Infants and children, 18(2), 86-103.
- Hodapp, R.M., DesJardin, J.L. and Ricci, L.A. (2003). Genetic syndromes of
mental retardation: Should they matter for the early interventionist? Infants
and Young Children. 16(2), 152-160.
- Hodapp, R.M. and Freeman, S.F.N. (2003). Advances in educational strategies
for children with Down syndrome. Current Opinion in Psychiatry, 16, 511-516.
- Buckley, S. (2005). Specificity in Down syndrome. Down Syndrome News and
Update, 4(3), 81-86.[Open Access Full Text
]
- Buckley, S. (2000). Speech and language development for individuals with Down
syndrome - An overview. Portsmouth UK: Down Syndrome Education International.
[Open Access Full
Text
]
- Buckley, S. (2001). Reading and writing for individuals with Down syndrome -
An overview. Portsmouth UK: Down Syndrome Education International. [Open
Access Full Text
]
- Van Kraayenoord, C.E., Moni, K.B., Jobling, A. and Ziebarth, K. (2002).
Broadening approaches to literacy education for young adults with Down syndrome.
In M. Cuskelly, A. Jobling and S. Buckley (Eds.). Down syndrome across the life
span (pp. 81-920). London, England: Whurr Publishers Ltd.