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.