Editorial
Editorial from Down Syndrome Research and Practice, Volume 8, Issue 3.
. Editorial. Down Syndrome Research and Practice. 2003;8(3).
doi:10.3104/editorials.406
In this issue, we have papers on four independent topics, the effects of probable
Alzheimer disease on speech, language and memory function, the links between early
reading skills and phonological awareness, the effects of visual feedback on movement
and sleep related breathing disorders in adults with Down syndrome.
The first paper, entitled Françoise, a fifteen year follow-up,
from Jean Rondal and his colleagues M. Elbouz, M. Ylieff, and L. Docquier, at the
University of Liège in Belgium presents an individual case study that describes
in detail the changes in language and memory function of Françoise, a 47 year old
lady with Down syndrome. Françoise will already be well known to many in this field
as she developed exceptionally good spoken language abilities in her earlier years
and Rondal published a detailed study of her language, memory and cognitive skills
in 1995.[1] In 2000, the day centre that Françoise
attended became concerned about changes in her behaviour and requested further investigation.
This case study is of particular interest because Françoise had exceptionally good
language abilities for a person with Down syndrome. It is therefore possible to
identify subtle changes in her abilities which would not be evident in adults with
more typical language abilities. The assessments revealed that in 2002, Françoise
had relatively preserved articulatory skills though more dysfluencies and slower
speech rate than previously. She showed considerable word finding difficulties and
a significant deterioration in syntactic comprehension abilities. Her MLU had decreased
but she still had basically preserved morphosyntax in her spontaneous speech, maintaining
correct French word order and correctly marking gender, number, case, tense or aspect.
Her short-term memory span for digits and words had decreased, and her sentence
span had decreased very significantly. Rondal and colleagues review in detail the
findings with regard to loss of language and memory skills in Alzheimer patients
in the typical population and identify that Françoise's profile is similar – relatively
spared syntactic production skills but greater difficulty with semantic comprehension
of sentences. The authors suggest that the difficulty in sentence comprehension
tasks may be linked to impairment of central executive function rather than verbal
short-term memory per se. They also provide a useful review of the studies of ageing
and cognitive change in individuals with Down syndrome, identifying well preserved
skills in the majority. They discuss possible explanations of the profile of language
deterioration seen in both Françoise and typical adults with probable Alzheimer
disease and suggest that differential effects on implicit or explicit memory systems
or differential effects on a modular language system could be explanations at this
point in our knowledge of the processes involved. This paper is a unique and valuable
addition to the literature on dementia in Down syndrome.
The second paper, entitled Early phonological awareness and reading
skills in children with Down syndrome, from Esther Kennedy and Mark Flynn
of the Ministry of Education and the University of Canterbury, New Zealand, explores
the phonological skills of beginning readers. In typical developing children, phonological
awareness skills have been shown to be both predictors of reading ability in children,
and to develop with reading instruction and reading progress. The authors point
out that some researchers, including the Editor and colleagues, have suggested that
children with Down syndrome make less use than typical children of the phonological
(alphabetic) information provided by the letters in words when reading in the early
years and rely to a greater extent on the whole word visual (logographic) features.
Children with Down syndrome begin to show more phonological awareness and the ability
to read non-words when they reach word reading skills of 7 to 8 years i.e. as a
result of reading experience.[2] Other researchers
argue that a minimum level of phonological awareness and of short-term memory skills
(digit span) are prerequisites for reading. These conflicting views are difficult
to resolve as tasks designed to measure phonological awareness, particularly when
involving judgements of rhyme or requiring phonemic isolation and blending are frequently
too difficult for children with Down syndrome who are beginning readers. This paper
reports the findings of a study of reading and phonological awareness skills of
9 children with Down syndrome. In addition to developing tests to assess rhyme awareness,
alliteration, phoneme blending, phoneme isolation and non-word reading skills, the
researchers also include measures of consonant production skill, speech perception
skills and hearing. The children, as in other studies, found the phonological awareness
tasks difficult, with only 3 able to score above chance on phoneme blending, 1 child
on the rhyme task, 4 on phoneme isolation and alliteration, and 3 on non-word reading.
In contrast, all 9 children scored above chance on letter naming and 7 on letter
sound knowledge. Alliteration (requiring identification of initial sounds in words
only), letter naming and letter sound knowledge were the only skills significantly
correlated with word reading abilities. Letter names and letter sounds are taught
to children and the initial sounds likely to be the first phonemes identified in
printed words. It can be argued therefore that these skills are all the result of
reading instruction and improve with reading success. Interestingly, speech perception
skills were correlated with speech intelligibility but not pure tone audiometry
results, indicating the importance of assessing speech perception skills in addition
to traditional hearing assessments, to guide therapy programmes. Speech perception
skills were not correlated with any other measures. It may be the poor speech perception
and speech sound production skills in children with Down syndrome that delay their
development of an awareness of the sounds which make up words, until they receive
explicit instruction on phonemes as part of literacy teaching. Explicit speech sound
discrimination activities and games designed to teach them to be aware of alliteration
and rhyme during their preschool years might be beneficial. This study, while limited
by the numbers of children participating, should encourage others to continue to
develop methods to explore these issues further and the authors propose directions
for further research.
The third paper, entitled Performing movement sequences with knowledge
of results under different visual conditions in adults with Down syndrome,
from Naznin Virji-Babul, Jennifer Lloyd and Geraldine Van Gyn of the Down Syndrome
Research Foundation and the University of Victoria, Canada, addresses the issue
of the role of visual information when learning movements. Until recently the study
of the development of the movement skills of children and adults with Down syndrome
has been a neglected area. Many authors identify 'clumsiness', slowness and variability
of movements as characteristic of individuals with Down syndrome but little is known
about the reasons for this profile. In this paper, the authors compare the performance
of 10 adults with Down syndrome with 14 neurologically 'typical' adults when required
to carry out a task which involved completing a sequence of button presses as quickly
as possible. Reaction times and movement times were measured under 2 conditions
– full visual feedback, with full view of arms and hands, and no visual feedback,
when participants could not see arms and hands but the buttons on the board were
still visible. The results indicate that neither movement time nor reaction time
were affected by visual feedback for either group of participants. The authors suggest
that this indicates that individuals with Down syndrome do not have any proprioceptive
deficits as proprioceptive feedback alone allowed them to perform the task successfully.
However, fingertip positions must have been visible as they touched buttons in the
'no visual feedback' conditions, and perhaps this was sufficient visual information
for success in this task. The typical adults showed no improvement in performance
over the trials in the study but the adults with Down syndrome showed considerable
improvement, still continuing at the final 20th trial. This confirms the findings
of other researchers which indicate that many adults with Down syndrome have not
fully developed their motor skills as they show considerable improvements with training.
As the authors point out, this improvement during the study means that in future,
research designs should allow all participants to reach their best performance levels
before making comparisons between groups.
The final paper, entitled Sleep related breathing disorders in adults
with Down syndrome from Onofria Resta, Maria Barbaro and colleagues from
the Universities of Bari and Foggia in Italy, provides information on the type and
incidence of sleep disorders in adults. In this study, the nocturnal respiratory
patterns of 6 adults were monitored for an 8 hour night period. Oxygen saturation
levels and breathing patterns were monitored in addition to the information provided
by a 12 channel polysomnograph. The study indicated high levels of sleep disturbance.
Five of the 6 adults had sleep apnoea, the majority (89.2%) of the apnoeic episodes
were obstructive rather than central (10.8%). Some 70% of the apnoeic episodes induced
significant oxygen desaturation. The authors compare their findings with the small
number of other published studies, some of which indicate that, as in the general
population, age and weight are risk factors in sleep apnoea in adults with Down
syndrome, although this was not demonstrated in this study. The authors do not comment
on the possible effects of such a high incidence of sleep apnoea and accompanying
oxygen desaturation on the health, learning abilities or day-time behaviour of those
affected. This would seem an important area for future study – for both adults and
children with Down syndrome – as there is already some evidence of effects of sleep
disturbance on daytime behaviour in children.[3]
References
- Rondal, J.A. (1995). Exceptional language development
in Down syndrome. Implications for the cognition language relationship. New
York: Cambridge University Press.
- Buckley, S. (2001). Reading and writing for individuals
with Down syndrome - an overview. Portsmouth, UK. Down Syndrome Educational
Trust.
- Stores, R., Stores G., Fellows, B. & Buckley, S. (1998).
Daytime behaviour problems and maternal stress in children with Down syndrome, their
siblings, their non-intellectually disabled and other intellectually disabled peers.
Journal of Intellectual Disability Research, 42S(3), 228-237.