published_or_final_version / Social Work / Master / Master of Social Work

published_or_final_version / abstract / toc / Educational Psychology / Master / Master of Social Sciences

published_or_final_version / Obstetrics and Gynaecology / Master / Master of Philosophy

published_or_final_version / abstract / Speech and Hearing Sciences / Master / Master of Science in Audiology

Children with Down syndrome (DS) are reported to experience difficulty with spoken and written language which can persist through the lifespan. However, little is known about the spoken and written language profiles of children with DS in the New Zealand social and education environment, and a thorough investigation of these profiles has yet to be conducted. The few controlled interventions to remediate language deficits in children with DS that are reported in the literature typically focus on remediation of a single language domain, with the effectiveness of interventions which integrate spoken and written language goals yet to be explored for this population. The experiments reported in this thesis aim to address these areas of need. The following questions are asked 1) What are the phonological awareness, speech, language and literacy skills of New Zealand children with DS? 2) What are the home and school literacy environments of New Zealand children with DS and how do they support written language development? and 3) What are the immediate and longer term effects of an integrated phonological awareness intervention on enhancing aspects of spoken and written language development in young children with DS? These questions will be addressed through the following chapters. The first experiment (presented in Chapter 2) was conducted in two parts. Part 1 consisted of the screening of the early developing phonological awareness, letter knowledge, and decoding skills of 77 primary school children with DS and revealed considerable variability between participants on all measures. Although some children were able to demonstrate mastery of the phoneme identity and letter knowledge skills, floor effects were also apparent. Data were analysed by age group (5 - 8 years and 9 -14 years) which revealed increased performance with maturation, with older children outperforming their younger peers on all measures. Approximately one quarter of all children were unable to decode any words, 6.6% demonstrated decoding skills at a level expected for 7 - 8 year old children and one child demonstrated decoding skills at an age equivalent level. Significant relationships between decoding skills and letter knowledge were found to exist. In Part 2 of the experiment, 27 children with DS who participated in the screening study took part in an in-depth investigation into their speech, phonological awareness, reading accuracy and comprehension and narrative language skills. Results of the speech assessments revealed the participants’ speech was qualitatively and quantitatively similar to the speech of younger children with typical development, but that elements of disorder were also evident. Results of the phonological awareness measures indicated participants were more successful with blending than with segmentation at both sentence and syllable level. Rhyme generation scores were particularly low. Reading accuracy scores were in advance of reading comprehension, with strong relationships demonstrated between reading accuracy and phonological awareness and letter knowledge. Those children who were better readers also had better language skills, producing longer sentences and using a greater number of different words in their narratives. The production of more advanced narrative structures was restricted to better readers. In the second experiment (presented in Chapter 3), the home literacy environment of 85 primary school aged children with DS was investigated. Parents of participants completed a questionnaire which explored the frequency and duration of literacy interactions, other ways parents support and facilitate literacy, parents’ priorities for their children at school, and the child’s literacy skills. Results revealed that the homes of participants were generally rich in literacy resources, and that parents and children read together regularly, although many children were reported to take a passive role duding joint story reading. Many parents also reported actively teaching their child letter names and sounds and encouraging literacy development in other ways such as language games, computer use, television viewing and library access. Writing at home was much less frequent than reading, and the allocation of written homework was much less common than reading homework. In the third experiment (presented in Chapter 4), the school literacy environment of 87 primary school aged children with DS (identified in the second experiment) was explored. In a parallel survey to the one described in Chapter 3, the teachers of participants completed a questionnaire which explored the frequency and duration of literacy interactions, the role of the child during literacy interactions, the child’s literacy skills, and other ways literacy is supported. The results of the questionnaire revealed nearly all children took part in regular reading instruction in the classroom although the amount of time reportedly dedicated to reading instruction was extremely variable amongst respondents. The average amount of time spent on reading instruction was consistent with that reported nationally and in advance of the international average for Year 5 children. Reading instruction was typically given in small groups or in a one on one setting and included both ‘top-down’ and bottom up’ strategies. Children were more likely to be assigned reading homework compared to written homework, with writing activities and instruction reported to be particularly challenging. In the fourth experiment (reported in Chapter 5), the effectiveness of an experimental integrated phonological awareness intervention was evaluated for ten children with DS, who ranged in age from 4;04 to 5;05 (M = 4;11, SD = 4.08 months). The study employed a multiple single-subject design to evaluate the effect of the intervention on participants’ trained and untrained speech measures, and examined the development of letter knowledge and phonological awareness skills. The 18 week intervention included the following three components; 1. parent implemented print referencing during joint story reading, 2. speech goals integrated with letter knowledge and phoneme awareness activities conducted by the speech-language therapist (SLT) in a play based format, and 3. letter knowledge and phoneme awareness activities conducted by the computer specialist (CS) adapted for presentation on a computer. The intervention was implemented by the SLT and CS at an early intervention centre during two 20 minute sessions per week, in two 6 week therapy blocks separated by a 6 week break (i.e. 8 hours total). The parents implemented the print referencing component in four 10 minute sessions per week across the 18 week intervention period (approximately 12 hours total). Results of the intervention revealed all ten children made statistically significant gains on their trained and untrained speech targets with some children demonstrating transfer to other phonemes in the same sound class. Six children demonstrated gains in letter knowledge and nine children achieved higher scores on phonological awareness measures at post-intervention, however all phonological awareness scores were below chance. The findings demonstrated that dedicating some intervention time to facilitating the participants’ letter knowledge and phonological awareness was not at the expense of speech gains. The fifth experiment (presented in Chapter 6) comprises a re-evaluation of the speech, phonological awareness, and letter knowledge, and an evaluation of the decoding and spelling development in children with DS who had previously participated in an integrated phonological awareness intervention (see Chapter 5), after they had subsequently received two terms (approximately 20 weeks) of formal schooling. Speech accuracy was higher at follow-up than at post-intervention on standardised speech measures and individual speech targets for the group as a whole, with eight of the ten participants demonstrating increased scores on their individual speech targets. Group scores on both letter knowledge measures were higher at follow-up than at post-intervention, with nine participants maintaining or improving on post-intervention performance. The majority of participants exhibited higher phonological awareness scores at follow-up on both the phoneme level assessments, with above chance scores achieved by five participants on one of the tasks, however, scores on the rhyme matching task demonstrated no evidence of growth. Some transfer of phonological awareness and letter knowledge was evident, with five children able to decode some words on the single word reading test and three children able to represent phonemes correctly in the experimental spelling task. The emergence of these early literacy skills highlighted the need for ongoing monitoring of children’s ability to transfer their improved phonological awareness and letter knowledge to decoding and spelling performance. In the sixth experiment (presented in Chapter 7) the long term effects of the integrated phonological awareness intervention was evaluated for one boy with DS aged 5;2 at the start of the intervention. The study monitored Ben’s speech and literacy development up to the age of 8;0 (34 months post pre-school intervention) which included two years of formal schooling. Ben demonstrated sustained growth on all measures with evidence of a growing ability to transfer letter-sound knowledge and phoneme-grapheme correspondences to the reading and spelling process. The results indicated an intervention which is provided early and which simultaneously targets speech, letter knowledge and phonological awareness goals provides a promising alternative to conventional therapy, and that integrating spoken and written therapy goals for children with DS can be effective in facilitating development in both domains. This thesis provides evidence that the spoken and written language abilities of New Zealand children with DS exhibit a pattern of delay and disorder that is largely consistent with those of children with DS from other countries reported in the literature. The home and school literacy environments of children in New Zealand with DS are rich in literacy resources and are, for the most part, supportive of their literacy development. The immediate and longer term results of the integrated phonological awareness intervention suggest that it is possible to achieve significant and sustained gains in speech, letter knowledge and phonological awareness which may contribute to the remediation of the persistent and compromised spoken and written language profile characteristic of individuals with DS.

Behavioral data in individuals with Down syndrome (DS) and mouse models of the syndrome suggest impaired object processing. In this study we examined the component processes that may contribute to object memory deficits. A neuropsychological test battery was administered to individuals with DS (n=28), including tests targeting perirhinal cortex (PRC) and prefrontal cortex (PFC) function, tests of perception (i.e., convexity based figure ground perception), and tests of memory (object recognition and object-in-place learning). To compare to individuals with DS, the same number of typically developing chronological age (CA, n=28) and mental age-matched (MA, n=28) controls were recruited. We observed object memory deficits in DS (p<0.001). In contrast, the DS group showed relatively intact use of convexity when making figure-ground judgments and spared PRC-dependent function, as compared to MA control. In addition, measures of PFC function seemed to be related to performance on object recognition tasks. These findings suggest that the inputs into the MTL from low and high level perceptual processing streams may be intact in DS. The object memory deficits we observed might reflect impaired PFC function.

The research presented in this thesis combined a number of aims. One was to investigate in detail the early typical development of individual cognitive domains including attention, literacy and numeracy, and consequently to investigate whether domain-general attentional abilities constrain the development of either literacy or numeracy skills in preschool to school-age children. A further aim was to test the development of the same cognitive processes in two groups of children with developmental disorders of known genetic origin; Down syndrome (DS) and Williams syndrome (WS). A combination of standardised tests, novel experimental paradigms, and questionnaire measures were employed in pursuit of these aims, and children were assessed both cross-sectionally and longitudinally one year later. In typically developing (TD) children, novel findings pointed to differential influences of cognitive constructs of sustained and selective attention on the one hand, and executive attention on the other, on reading and numeracy abilities longitudinally. In both of the atypically developing groups of children, novel and individual patterns of developmental relationships emerged in the domains of attention, literacy and numeracy. In addition, the investigation of cross-domain relationships between attentional abilities and literacy and numeracy skills evidenced typical patterns in DS children, but atypical patterns in WS children. These findings emphasize the importance of cross-syndrome, cross-domain, and fully developmental research to understand both typical and atypical profiles of cognitive development. Furthermore, teaching practice, early identification of difficulties, and interventions should consider the wider implications of potential constraints of broader cognitive domains, such as attention, on learning.

Background: Children with Down syndrome (DS) have increased risk for developing AML (DS-AMKL), and they usually experience severe therapy-related toxicities compared to non DS-AMKL. Refractory/ relapsed disease has very poor outcome, and patients would benefit from novel, less toxic, therapeutic strategies that overcome resistance. Relapse/resistance are linked to cancer stem cells with high aldehyde dehydrogenase (ALDH) activity. The purpose of the present work was to study less toxic alternative therapeutic agents for relapsed/refractory DS-AMKL. Methods: Fourteen AML cell lines including the DS-AMKL CMY and CMK from relapsed/refractory AML were used. Cytarabine (Ara-C), bortezomib (BTZ), disulfiram/copper (DSF/Cu2+) were evaluated for cytotoxicity, depletion of ALDH-positive cells, and resistance. BTZ-resistant CMY and CMK variants were generated by continuous BTZ treatment. Cell viability was assessed using CellTiter-Glo((R)), ALDH activity by ALDELUOR(TM), and proteasome inhibition by western blot of ubiquitinated proteins and the Proteasome-Glo(TM) Chymotrypsin-Like (CT-like) assay, apoptosis by Annexin V Fluos/Propidium iodide staining, and mutations were detected using PCR, cloning and sequencing. Results: Ara-C-resistant AML cell lines were sensitive to BTZ and DSF/Cu2+. The Ara-C-resistant DS-AMKL CMY cells had a high percentage of ALDHbright "stem-like" populations that may underlie Ara-C resistance. One percent of these cells were still resistant to BTZ but sensitive to DSF/Cu2+. To understand the mechanism of BTZ resistance, BTZ resistant (CMY-BR) and (CMK-BR) were generated. A novel mutation PSMB5 Q62P underlied BTZ resistance, and was associated with an overexpression of the beta 5 proteasome subunit. BTZ-resistance conferred increased resistance toAra-C due to G1 arrest in the CMY-BR cells, which protected the cells from S-phase damage by Ara-C. CMY-BR and CMK-BR cells were cross-resistant to CFZ and MG-132 but sensitive to DSF/Cu2+. In this setting, DSF/Cu2+ induced apoptosis and proteasome inhibition independent of CT-like activity inhibition. Conclusions: We provide evidence that DSF/Cu2+ overcomes Ara-C and BTZ resistance in cell lines from DS-AMKL patients. A novel mutation underlying BTZ resistance was detected that may identify BTZ-resistant patients, who may not benefit from treatment with CFZ or Ara-C, but may be responsive to DSF/Cu2+. Our findings support the clinical development of DSF/Cu2+ as a less toxic efficacious treatment approach in patients with relapsed/refractory DS-AMKL.

The aim of this experiment was to study whether completing a questionnaire either related or unrelated to various aspects of the workplace could induce different implicit and explicit stereotypic associations with Down syndrome. Subjects read one of three questionnaires before completing a task designed to measure implicit associations. The task consisted of photo primes of faces belonging to individuals with Down syndrome and typically developing individuals, followed by an evaluative decision task with adjectives related to the stereotype dimensions of warmth and competence. Following the implicit task, participants were asked directly about their associations between Down syndrome and each of the target traits. It was hypothesized that Down syndrome would be systematically associated with low competence, regardless of the context primed, but that it would be associated with greater warmth when morale-related aspects of the workplace were primed than when efficiency-related aspects of the workplace were primed. These hypotheses were not supported, and questionnaire type did not seem to prime specific associations in the implicit task. However, consistent with past research, Down syndrome was associated with high ratings of warmth on the explicit measure, and implicit results suggest Down syndrome may be implicitly associated with greater warmth as well. Methodological limitations of the study are discussed, as well as possible directions for future research.

M.Ed. (Education) / Please refer to full text to view abstract