Dr Hana D'Souza

(she/her)

Research

Summaries of our research for parents and practitioners

Development is a complex process with many factors at play. We study a range of these factors, including motor abilities, attention, sleep, parental mental health, health comorbidities, and genes, in order to learn how young children with genetic syndromes develop.

Here are some of the more recent findings from our research on young children with Down syndrome, fragile X syndrome, and Williams syndrome.

This is by no means definitive and there are many more issues to be investigated and further understood. However, sharing these findings is important as they can help parents and practitioners to better understand how young children develop.

We would like to thank all the families, practitioners, and funders who made this research possible.

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The emerging phenotype in infants with Down syndrome: Adaptations to atypical constraints

Emerging phenotype

Development is a complex process. To understand early development in Down syndrome (DS), we need to integrate findings from across disciplines within an overarching approach or framework. The approach we take is to view DS not as a collection of cognitive and motor deficits, nor as an assortment of relative strengths and weaknesses, but as a functioning adaptive system albeit with a different start state (trisomy 21).  According to this view, the emerging characteristics of DS are adaptations to atypical constraints, and thus serve an immediate functional purpose – but these early adaptations will in turn act as new developmental constraints, and some of them may exacerbate the divergence of the DS trajectories.

Here we focus on the first few years after birth, because to understand how the DS phenotype gradually emerges, it is important to focus on early developmental constraints. We start by introducing DS as an adaptive system with trisomy 21, and how a developmental systems approach is needed to understand it. We continue by explaining how such an approach can be implemented in research. We then describe how trisomy 21 may constrain neural plasticity, which is likely to have cascading effects on the developmental process of specialization – contributing to less efficient information processing and atypical motor activity. We then discuss how young children with DS may adapt to these challenges within the context of the social environment. Finally, we point to future directions in theory, research, and intervention.

Key points for parents and practitioners

• The development of all children (including children with Down syndrome) is a dynamic process in which a lot of factors interact. It is not genetically predetermined.
• Later development (e.g., the ability to learn words) builds on earlier experiences (e.g., the ability to hear and distinguish speech sounds).
• Every child (including children with Down syndrome) adapts to their environment. Where children with Down syndrome struggle to develop key skills in a typical way, they tend to employ alternative adaptive strategies. Although these strategies can yield immediate benefits, they may restrict the child's later experiences, affecting their developmental trajectory.
• Constraints on motor abilities in infants with Down syndrome are likely to have cascading effects on other aspects of development, including social development.
• Infants with Down syndrome may rely more on (and imitate more) those around them in social situations. This could be a useful short-term adaptive solution to challenges in the present, but it may constrain the development of their independent behaviour in the long term.

Figure above:  Illustration of cascading effects and the complexity of development across time. Horizontal arrows = trajectories within a domain of functioning; Diagonal arrows = causal pathways within levels of functioning;  Vertical arrows = effects between levels of functioning.  Adapted from Moore & George (2015).

Publication: D'Souza, H., & D'Souza, D. (2022). The emerging phenotype in infants with Down syndrome: Adaptations to atypical constraints. In J. Burack, J. Edgin, & L. Abbeduto (Eds.), The Oxford Handbook of Down Syndrome and Development. Oxford University Press. https://doi.org/10.1093/oxfordhb/9780190645441.001.0001

Invited keynote based on this publication presented at the Down Syndrome Research Forum in March 2022: https://www.down-syndrome.org/en-gb/research/forum/2022/program

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Associations between the APOE ε4 gene and attentional abilities across the lifespan in individuals with Down syndrome

APOE

How we use our attention impacts how we learn and develop. Many different factors affect people's attentional abilities. This is also true for individuals with Down syndrome. One of these factors is genetics.

In this study, we looked at a particular gene known as APOE. We measured the attentional abilities of children and adults with Down syndrome, some of whom carried a particular type of the APOE gene (ε4), and some of whom did not. The children's attentional ability was measured using remote eye-tracking as in our study below, and the adults' attentional ability was measured using a reaction time task. We discovered that individuals with Down syndrome who carry the APOE ε4 gene are likely to have higher attentional ability as young children, but lower attentional ability as older adults.

Understanding this gene can help us to create better interventions for people with Down syndrome, especially when we consider genetics alongside other factors that affect development, such as family context and wider support.

Figure above:  Illustration of cascading effects and the complexity of development across time. Horizontal arrows = trajectories within a domain of functioning; Diagonal arrows = causal pathways within levels of functioning;  Vertical arrows = effects between levels of functioning.  Adapted from Moore & George (2015).

Publication:  D'Souza, H., Mason, L., Mok, K. Y., Startin, C. M., Hamburg, S., Hithersay, R., ... Thomas, M. S. C. (2020). Differential associations of apolipoprotein E ε4 genotype with attentional abilities across the life span of individuals with Down syndrome. JAMA Network Open, 3(9), e2018221.  https://doi.org/10.1001/jamanetworkopen.2020.18221

This research was conducted in collaboration with the LonDownS Consortium.

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Attentional abilities and language development in infants and toddlers with Down syndrome, fragile X syndrome, and Williams syndrome

Fragile X syndrome

The ability to visually focus on something, and to move this attention to something else when relevant, is very important for learning and development. This is known as visual orienting. Until now, very little was known about visual orienting in infants and toddlers with neurodevelopmental disorders other than autism.

Our recent research studied visual orienting in infants and toddlers with Down syndrome, fragile X syndrome, and Williams syndrome. We used remote eye-tracking to measure visual orientation, and also assessed language ability.

We found that young children with Down syndrome are slower than typically developing children at disengaging and shifting their visual attention to something else. We also found that, irrespective of the group, faster shifting was related to better language ability. These findings suggest that the visual disengagement difficulties in young children with Down syndrome may contribute to language delay.

Publication:  D'Souza, D., D'Souza, H., Jones, E. J., & Karmiloff‐Smith, A. (2020). Attentional abilities constrain language development: A cross‐syndrome infant/toddler study. Developmental Science, e12961.  https://doi.org/10.1111/desc.12961

This research was conducted in collaboration with the ELAN lab.

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Parental depression and language development in infants and toddlers with Down syndrome

Parental depression

In the general population, parental depression is often associated with difficulties in child language development. In this study, we measured the development of language, motor, and cognitive abilities in young children with Down syndrome from 8 months up to the age of 4 years, alongside parental depression.

We found that in cases where parents reported depression, the child's ability to express language developed at a slower rate. It may therefore be especially important to support these families.

Publication: D'Souza, H., Lathan, A., Karmiloff-Smith, A., & Mareschal, D. (2020). Down syndrome and parental depression: A double hit on early expressive language development. Research in Developmental Disabilities, 100, 103613.  https://doi.org/10.1016/j.ridd.2020.103613

This research was conducted in collaboration with the LonDownS Consortium.

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Sleep and language development in infants and toddlers with Down syndrome, fragile X syndrome, and Williams syndrome

Sleep and language

We found that sleep is disrupted for infants and toddlers with Down syndrome, fragile X syndrome, and Williams syndrome. During the night these infants/toddlers slept less and woke for longer than is typical, in the general population, for their chronological age.

Importantly, the more sleep children with Down syndrome and Williams syndrome had, the larger their receptive vocabulary (understanding of words). This could not be analysed for those with fragile X syndrome due to low numbers of participants.

The findings suggest that from a young age, sleep is disrupted in these genetic syndromes and may impact on the child's language development. Finding ways to improve sleep early on in childhood may be an important step for improving language development.

Press release

Publication: D'Souza, D., D'Souza, H., Horváth, K., Plunkett, K., & Karmiloff-Smith, A. (2020). Sleep is atypical across neurodevelopmental disorders in infants and toddlers: A cross-syndrome study. Research in Developmental Disabilities, 97, 103549.  https://doi.org/10.1016/j.ridd.2019.103549

This research was conducted in collaboration with the ELAN lab.

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Health comorbidities and cognitive abilities across the lifespan in Down syndrome

Lifespan in Down's Syndrome

Many people with Down syndrome have co-occurring multiple health issues. We have conducted research to see prevalence of different health issues in the LonDownS cohort. Medical history was collated for 602 individuals with Down syndrome from 3 months to 73 years.

Implications for clinical practice

• Clinical guidance tends to be focussed on the needs of children with DS, but the pattern of comorbidities varies across the lifespan and surveillance needs to be adapted accordingly:
  • Epilepsy is more common in older adults compared to other age groups, and this is likely associated with the development of dementia.
  • Obstructive sleep apnoea requires on-going surveillance throughout the lifespan.
  • Thyroid disorders, particularly hypothyroidism, become more common with ageing.
  • Reflux is a common concern in children with DS.
  • Hearing and vision problems remain an important consideration throughout life, but these have different causes at different ages.
    • For hearing, otitis media with effusion is a common issue in childhood, while other causes of hearing loss become important in adulthood.
    • Vision problems increase across the lifespan, with the increased occurrence of cataracts in adulthood.
• Unlike in the typically developing population, most mental health conditions are equally common in males and females, requiring similar surveillance in both sexes to ensure equitable care.
• Neurodevelopmental disorders such as autism and ADHD are relatively common and do not show the same sex patterns as in the general population. These should be included in assessment and treatment guidance for all individuals.
• To improve cognitive outcomes, a focus on interventions for those with DS from lower SES families and for those with autism or epilepsy is required.

Adapted from Table 7

Publication:  Startin, C. M., D'Souza, H., Ball, G., Hamburg, S., Hithersay, R., Hughes, K. M., ... Strydom, A. (2020). Health comorbidities and cognitive abilities across the lifespan in Down syndrome. Journal of Neurodevelopmental Disorders, 12(1), 4.  https://doi.org/10.1186/s11689-019-9306-9

This research was conducted in collaboration with the LonDownS Consortium.

Teaching

Cardiff University

Psychology (BSc)

I contribute to the following modules:

• PS1014 Psychological Research
• PS2020 Language and Memory 
• PS3000 Research Project
• Placement

Biography

Academic positions

• 2024 - present: UKRI Future Leaders Fellow & Senior Lecturer (Associate Professor), School of Psychology, Cardiff University, UK
• 2022 - 2024: Lecturer (Assistant Professor), School of Psychology, Cardiff University, UK
• 2018 - 2022: Beatrice Mary Dale Research Fellow, Newnham College, University of Cambridge, UK
• 2021 - 2022: Research Associate, Centre for Family Research, University of Cambridge, UK
• 2015 - 2018: Postdoctoral Research Fellow, Centre for Brain & Cognitive Development (CBCD), Birkbeck, University of London, UK & LonDownS Consortium
• 2015 - 2016: Postdoctoral Research Associate, UCL, UK

Education

• 2012 - 2016: PhD in Psychology, Goldsmiths, University of London, UK
  • Thesis: Specialization of the motor system in typically developing infants and infants with Down syndrome (viva with no corrections); Supervisors: Dr Andrew Bremner & Prof Annette Karmiloff-Smith

• 2015: Visiting Doctoral Student, University of Michigan at Ann Arbor, USA
• 2013 - 2015: PGCert in Management of Learning & Teaching in Higher Education, Goldsmiths, University of London, UK
• 2011 - 2012: MSc in Psychological Research, University of Oxford, UK
• 2005 - 2011: Master's degree (Mgr.) (5 years) in Psychology, graduated in Clinical Psychology, Masaryk University, Czech Republic
• 2009 - 2010: International Exchange Student in Psychology, University of Toronto, Canada
• 2005 - 2009: Bachelor's degree (Bc.) in Psychology & Media Studies and Journalism (Double), Masaryk University, Czech Republic

Supervisions

Future PhD students

Funded PhD studentships

There are a number of PhD schemes depending on the particular interest and background of the candidate.

Get in touch with Dr Hana D'Souza (dsouzah@cardiff.ac.uk) if you'd like to discuss PhD opportunities in Cardiff Babylab!

Current PhD students

Charlotte Bocchetta

Craig Thompson

Jean Liu

Kate Mee

Sofia Hryniv