Understanding cognitive delays in infants with Down syndrome
Down syndrome is a genetic disorder that affects around one in every 700 babies born in the US. It is characterized by intellectual disability, distinct physical features, and comorbidity with several medical and developmental disorders.
For example, people with Down syndrome experience growth delays and can be recognized by some of their characteristic facial features. They are also at risk for autism, epileptic seizures, and Alzheimer’s disease.
Furthermore, people with Down syndrome experience a general delay in cognitive development. Difficulties in this area are most pronounced in attention, memory, and executive function.
Factors of delayed development
In the current study, Fidler and her colleagues examined cognition in infants with Down syndrome. They argue that it is important to understand delays in early development better, so that preventative care can be improved.
Specifically, they focused on the relation between cognitive functioning and early attention and memory skills. During infancy, these include the ability to sustain and shift visual attention and the ability to temporarily store and retrieve visual information.
Another aim of the study was to examine whether biomedical factors play a role in the observed cognitive delays. For example, many infants with Down syndrome are born with heart defects, are born prematurely, or experience significant illness.
These factors are known to impact cognition in the general population, but have not been examined in a population of infants with Down syndrome before.
Participant characteristics
Fidler and her team included 38 infants with Down syndrome in their study. Cognitive functioning was assessed using the Bayley Scales of Infant and Toddler Development. While the mean chronological age was nine months, the mean cognitive age was six months.
Of these participants, 13 infants were born prematurely, 11 were diagnosed with a congenital heart defect, and five had had a significant illness.
Measuring attention and memory
Infant attention and memory behaviors were observed in three different tests and coded using The Observer XT.
The first test measured sustained attention, or focusing on a stimulus without interruption or distraction. To assess this skill, infants were presented with a red teether, and observed on total time spent looking at the teether.
The second test involved attention shifting. Infant attention shifting is observed as visual engagement with a stimulus, followed by disengaging and redirecting attention to a new stimulus.
In the experiment, this was tested by holding up a red ball to the left and a schematic face to the right, and alternately shaking them. In each trial, researchers coded the time it took infants to look at the object that was shaken, and the time between attention shifts.
In the third test, visual short-term memory was measured as time spent on exploration during a ‘changed preference’ task.
In this task, infants were presented with the same Lego in three consecutive trials. Researchers hypothesized that as the infants got used to the Lego, the time spent on visual exploration would decrease.
On the fourth trial, the experimenter presented a new Lego, different in color and size. If the infant remembered what the previous Lego looked like, it would recognize that this was a new Lego. As a result, time spent on exploration would increase again.
Associations with attention shifting
Results showed a clear association between attention shifting and cognitive development. Infants with lower cognitive performances were also slower to shift attention, even when controlling for chronological age.
When examining the role of biomedical factors in these results, Fidler and her colleagues found that premature birth was also associated with attention shifting.
The research team emphasized that they found a great deal of variability in their data, and that they didn’t use a comparison group. They also recommended doing longitudinal studies to examine whether early attention shifting predicts further developmental outcomes.
Still, as one of the first studies examining factors in early cognitive development, their study provides valuable insights that can be used in targeted treatments.
Specifically, knowledge like this can be used in early interventions, where cognitive development can be stimulated during periods of infant neuroplasticity.
References
- Fidler, D.; Schworer, E.; Will, E.; Patel, L.; Daunhauer, L. (2019). Correlates of early cognition in infants with Down syndrome. Journal of Intellectual Disability Research, 63(3), 205-214.
- https://www.cdc.gov/ncbddd/birthdefects/downsyndrome/data.html
- https://en.wikipedia.org/wiki/Down_syndrome
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