Evaluating an adapted reverse categorisation task to assess cognitive flexibility in young children with Down syndrome.

BACKGROUND: Accurate measurement of cognitive skills is necessary to advance both developmental and intervention science for individuals with Down syndrome (DS). This study evaluated the feasibility, developmental sensitivity and preliminary reliability of a reverse categorisation measure designed to assess cognitive flexibility in young children with DS. METHODS: Seventy-two children with DS ages 2.5-8 years completed an adapted version of a reverse categorisation task. Twenty-eight of the participants were assessed again 2 weeks later for retest reliability. RESULTS: This adapted measure demonstrated adequate feasibility and developmental sensitivity, and preliminary evidence for test-retest reliability when administered to children with DS in this age range. CONCLUSIONS: This adapted reverse categorisation measure may be useful for future developmental and treatment studies that target early foundations of cognitive flexibility in young children with DS. Additional recommendations for use of this measure are discussed.

Psychometric properties of inhibitory control measures among youth with Down syndrome.

BACKGROUND: Inhibitory control measures have been commonly used when assessing individuals with Down syndrome. However, minimal attention has been devoted to evaluating the appropriateness of specific assessments for use in this population, potentially leading to erroneous conclusions. This study aimed to examine the psychometric properties of measures of inhibitory control among youth with Down syndrome. We sought to examine the feasibility, presence of floor or practice effects, test-retest reliability, convergent validity and correlations with broader developmental domains of a set of inhibitory control tasks. METHODS: A sample of 97 youth with Down syndrome aged 6 to 17 years old participated in verbal and visuospatial tasks of inhibitory control including the Cat/dog Stroop, Neuropsychological Assessment Second Edition (NEPSY-II) Statue, National Institutes of Health (NIH) Toolbox Cognition Battery (TCB) Flanker, Leiter-3 Attention Sustained, and the Test of Attentional Performance for Children (KiTAP) Go/No-go and Distractibility subtests. Youth also completed standardised assessments of cognition and language, and caregivers completed rating scales. Psychometric properties on the tasks of inhibitory control were evaluated against a priori criteria. RESULTS: Apart from demonstrating negligible practice effects, adequate psychometric properties were not observed for any inhibitory control measure within the current sample's age range. One task with low working memory demands (NEPSY-II Statue) generally had better psychometric properties than the other tasks assessed. Subgroups of participants with an IQ greater than 30 and age more than 8 years were shown to be more likely to be able to complete the inhibition tasks. CONCLUSIONS: Findings suggest better feasibility for analogue tasks rather than computerised assessments of inhibitory control. Given the weak psychometrics of several common measures, future studies are required to evaluate other inhibitory control measures, specifically those with reduced working memory demands for youth with Down syndrome. Recommendations for use of the inhibitory control tasks among youth with Down syndrome are provided.

Acquisition of cognitive and communication milestones in infants with Down syndrome.

BACKGROUND: Understanding the timing of developmental milestones in typical and clinical populations facilitates intervention planning and the early detection of risk for co-occurring conditions. Normative timing of developmental milestone achievement has been established for typically developing children. However, there is little information regarding the timing of cognitive and communication skill acquisition in young children with Down syndrome (DS). The objectives of this study are to (1) provide foundational information regarding the timing of cognitive and communication skill acquisition in infants with DS and (2) facilitate the early identification of infants with risk for co-occurring conditions. METHOD: Seventy-four infants with DS (age range: 4-18 months) completed the Bayley Scales of Infant Development-III (Bayley 2006). Individual items from the cognitive and communication scales were selected for analysis. Parents provided information regarding their infant's developmental and family history. RESULTS: The percentage of infants who attained each skill was calculated within 2-month age bands. For infants who did not show skill acquisition within each age band, the rates of prematurity, heart defects, corrective heart surgery and significant illness were calculated as well. CONCLUSIONS: This study provides foundational information that can contribute to the formulation of a developmental schedule for cognitive and language milestone acquisition in infants with DS.

Early developmental profiles among infants with Down syndrome.

BACKGROUND: Down syndrome (DS) generally predisposes children to a pattern of relative developmental strengths and challenges, but within-syndrome heterogeneity is also commonly observed across many dimensions. The present research examines whether heterogeneity in developmental presentation can be detected during infancy in DS and whether factors associated with differing profiles can be identified. METHODS: Infants with DS (n = 75; age range: 3.9-17.6 months) were administered the Bayley Scales of Infant Development III (Bayley-III). A primary caregiver provided information regarding developmental history and family demographics. Latent profile analysis was conducted to identify whether early profiles were present across the five Bayley-III domains. RESULTS: Three developmental profiles were observable within the sample: a 'Mild Delay' Profile, an 'Moderate Delay' Profile and a 'Pronounced Delay' Profile. In addition, chronological age, having received heart surgery and having received occupational therapy were associated with probability of profile membership. CONCLUSIONS: Findings from this study contribute to the growing knowledgebase regarding heterogenous presentations associated with DS and can inform early intervention planning.

Latent profiles of autism symptoms in children and adolescents with Down syndrome.

BACKGROUND: Down syndrome (DS) is associated with elevated rates of autism spectrum disorder (ASD) and autism symptomatology. To better characterise heterogeneity in ASD symptomatology in DS, profiles of caregiver-reported ASD symptoms were modelled for children and adolescents with DS. METHODS: Participants (n = 125) were recruited through several multi-site research studies on cognition and language in DS. Using the Social Responsiveness Scale-2 (SRS-2; Constantino and Gruber 2012), two latent profile analyses (LPA) were performed, one on the broad composite scores of social communication and interaction and restricted interests and repetitive behaviour, and a second on the four social dimensions of social communication, social motivation, social awareness, and social cognition. RESULTS: A three-profile model was the best fit for both analyses, with each analysis yielding a low ASD symptom profile, an elevated or mixed ASD symptom profile and a high ASD symptom profile. Associations were observed between profile probability scores and IQ, the number of co-occurring biomedical conditions reported, sex, and SRS-2 form. CONCLUSIONS: Characterising heterogeneity in ASD symptom profiles can inform more personalised supports in this population, and implications for potential therapeutic approaches for individuals with DS are discussed.

Infant precursors of executive function in Down syndrome.

BACKGROUND: Although early features of infant cognition are predictive of executive function (EF) in typically developing (TD) children, there is little information regarding the developmental origins of EF in neurogenetic conditions, such as Down syndrome (DS). METHODS: The current study compared the performance of infants with and without DS on three dimensions that are hypothesised EF precursors: visual engagement, attention shifting and action planning. Additionally, the relationship between these EF precursors at Time 1 and EF performance at Time 2 (6 months later) was examined in the DS group. Participants were 36 infants with DS, M chronological age = 12.65 months, SD = 2.11; M developmental age = 8.84 months, SD = 2.22, and 36 TD infants, M chronological age = 8.62, SD = 3.06; M developmental age = 8.64 months, SD = 3.40. RESULTS: Infants with DS visually engaged with objects for longer durations and demonstrated challenges with action planning compared with TD infants at Time 1. Attention shifting at Time 1 significantly predicted EF performance at Time 2 in the DS group. CONCLUSIONS: This study provides evidence that an early atypical presentation of EF precursors is detectable during infancy in DS and is predictive of subsequent EF performance. These findings contribute to the identification of areas of early cognitive risk in DS and can inform future interventions in this population.

Evaluating working memory outcome measures for children with Down syndrome.

BACKGROUND: There is a critical need for the psychometric evaluation of outcome measures to be used in clinical trials targeting cognition in Down syndrome (DS). This study examines a specific cognitive skill that is of particular importance in DS, working memory, and the psychometric properties of a set of standardised measurements to assess working memory in individuals with DS. METHODS: Ninety children and adolescents ages 6 to 18 years old with DS were assessed on a selection of verbal and visuospatial working memory subtests of standardised clinical assessments at two time points to examine feasibility, distributional qualities, test-retest reliability and convergent validity against a priori criteria. Caregivers also completed an adaptive behaviour questionnaire to address working memory subtests' associations with broader developmental functioning. RESULTS: The Stanford Binet-5 Verbal Working Memory, Differential Ability Scales-2 Recognition of Pictures, Stanford Binet-5 Nonverbal Working Memory and Wechsler Intelligence Scale for Children-5 Picture Span measures met the most psychometric criteria overall across the full age and IQ range of the study. Although Differential Ability Scales-2 Recall of Sequential Order and Differential Ability Scales-2 Recall of Digits Backward met the fewest a priori criteria, follow-up analyses suggested greater feasibility in specific age and IQ ranges. CONCLUSIONS: Several working memory measures appear to be psychometrically sound and appropriate for use in clinical trials for children with DS, especially when focusing on raw scores. However, floor effects on standard scores and feasibility of some measures were problematic. Guidelines for use of the working memory subtests with this population are provided.

Executive function and intellectual disability: innovations, methods and treatment.

This editorial presents an introduction to and an overview of the current JIDR special issue on "Executive Function in Intellectual Disability." The articles included in this special issue provide a contemporary, in depth exploration of questions regarding the nature of EF in individuals with ID. Topics include the emergence of EF during early childhood in ID-related conditions, the influence of EF on other domains of development, and the relationship between EF and adaptation throughout the lifespan. This editorial synthesizes the findings presented in this special issue and identifies methodological challenges that researchers will continue to face in future investigations of this important area.

Feasibility of a syndrome-informed micro-intervention for infants with Down syndrome.

BACKGROUND: Infants with Down syndrome (DS) are at risk for a range of phenotypic outcomes, including delays in the onset of reaching behaviour, a critical skill that facilitates early learning. This parallel-group feasibility and pilot study presents findings from a parent-mediated micro-intervention that aimed to support the development of reaching behaviour in a sample of infants with DS. METHODS: Participants were 73 infants with DS and their caregivers. Infants who qualified for the home-based intervention (based on manual skill performance on Bayley Scales of Infant and Toddler Development, Third Edition items) were randomly assigned individually or by geographical region to a treatment or an alternative treatment condition that involved toy-based interactions with caregivers. Infants in the treatment condition experienced facilitated reaching during the toy-based interactions through the use of Velcro-affixed mittens and toys. RESULTS: Forty-two infants met criteria to participate in the intervention, and 37 participated in both baseline and post-treatment visits. At post-treatment, infants in the treatment condition demonstrated shorter latencies to make contact with objects and showed higher frequencies of reach attempts and swats at objects than infants in the alternative treatment group. These findings were more pronounced when examining a chronological age-restricted subgroup of infants 5 to 10 months. CONCLUSIONS: Findings suggest that a syndrome-informed approach to targeted intervention may be a promising application of phenotyping science in DS and other neurogenetic conditions associated with intellectual disability.

Goal-directed action planning in infants with Down syndrome.

BACKGROUND: Down syndrome (DS) is a neurogenetic disorder associated with risk for executive dysfunction, or difficulties with the cognitive processes required for planning volitional, goal-directed behaviour. This study examines the developmental origins of difficulties with goal-directed action planning in infants with DS to inform our understanding of the cognitive phenotype associated with DS and its implications for intervention. METHOD: First, the study compared the performance of infants with DS (n = 44, mean chronological age = 7.5 months, SD = 2.3) and typically developing infants (n = 31, mean chronological age = 7.5 months, SD = 2.9) on plan production and planning efficiency during an early planning task. Next, potential sources of variability in planning behaviour (motor performance and sensory processing) within the DS sample were examined. All infants completed an early planning laboratory task and the Bayley Scales of Infant Development-III Cognitive Scale. The motor and sensory skills of infants with DS were assessed by the motor scales of the Bayley Scales of Infant Development-III and the Infant Sensory Profile-2. DS-related biomedical history information was provided by caregivers for the infants with DS. RESULTS: Between-group differences in planning were observed on the dimensions of strategy production and completion, such that infants with DS were less efficient in their strategy execution than typically developing infants. In the DS group, motor skills and sensory processing were associated with planning efficiency on all components of the early planning task. CONCLUSIONS: Less efficient action planning in infants with DS may disrupt the shaping of goal-directed behaviour, and the identification of early risk factors associated with planning efficiency has important implications for early intervention.

Correlates of early cognition in infants with Down syndrome.

BACKGROUND: While delays in cognitive development are detectable during early development in Down syndrome, the neuropsychological and biomedical underpinnings of cognitive skill acquisition in this population remain poorly understood. METHOD: To explore this issue, 38 infants with Down syndrome [mean chronological age = 9.65 months; SD = 3.64] completed the Bayley Scales of Infant Development-III and a set of laboratory tasks that measured sustained attention (duration of visual attention during a 1-min object exploration task), attention shifting (mean latency to shift attention on an alternating object presentation task) and visual short-term memory (dishabituation to a novel object on a change preference task). RESULTS: Latency to shift attention was negatively associated with Bayley Cognitive Scale raw scores, even when controlling for the effects of chronological age, r (33) = -.41, P = .02. In addition, prematurity status was associated with latency to shift attention. CONCLUSIONS: Early attention shifting may be an important factor that facilitates overall cognitive skill acquisition in infants with Down syndrome, and premature birth may be a risk factor for difficulties on this dimension.

Parenting behaviour and executive function in children with Down syndrome.

BACKGROUND: Parenting behaviours influence many domains of child development, and recent work has demonstrated the specific effects of parenting on the development of executive function (EF) abilities. The relationship between parent-child interaction patterns and EF has been examined in typically developing (TD) children but has not yet been examined in dyads where the child has a diagnosis of Down syndrome (DS). METHOD: The current study examines the differences in patterns of parenting behaviours between DS dyads and dyads with TD children equated on nonverbal mental age. DS dyads (n = 42), child ages 59 to 118 months, and TD dyads (n = 28), child ages 30 to 49 months, participated in a modified version of the Parent-Child Challenge Task. Parent directive and teaching behaviours were coded, along with child compliance and noncompliance. Child participants also completed a laboratory measure of inhibition and working memory, and parents completed the Behaviour Rating Inventory of Executive Function-Preschool. RESULTS: There was a greater frequency of parenting directives and child compliance in the DS dyads, and parents of children with DS were more likely to follow child compliance with directives than parents of TD children. In both groups, parenting directive behaviour was a significant predictor of child EF laboratory performance. CONCLUSIONS: Results characterise the relationship between specific parenting behaviours and child EF in DS and TD dyads. The implications for parent training and intervention are discussed.

Executive function and academic achievement in primary - grade students with Down syndrome.

BACKGROUND: Executive function (EF) plays a critical role in academic outcomes in typically developing children, but the contribution of EF to academic performance in Down syndrome (DS) is less well understood. This study evaluated differences in early academic foundations between primary school aged children with DS and non-verbal mental-age matched typically developing (TD) children. Additionally, the contribution of EF domains to academic outcomes was evaluated in each group. METHOD: Participants with DS (n = 29) and mental-age matched TD participants (n = 23) were administered the Woodcock Johnson- III NU Tests of Academic Achievement, as well as a laboratory-based EF battery, including measures of working memory, shifting, inhibition and object-planning. RESULTS: Findings indicated a difference in early academic foundations profile between children with DS and mental-age matched TD children. Patterns of EF contributions towards academic outcomes were also observed across groups. CONCLUSIONS: Aspects of EF are critical to academic achievement in DS but differentially so relative to typical development. Implications for educational instruction are discussed.

Stress trajectories in mothers of young children with Down syndrome.

BACKGROUND: In this study, we investigated the early development of stress in mothers of children with Down syndrome, compared with mothers of children with developmental disabilities of mixed aetiologies. Growth modelling analyses were used to explore: (1) whether mothers of children with Down syndrome demonstrated distinct patterns of stress during their children's early development, compared with mothers of children with other developmental disabilities; and (2) whether there was a relation between child behavioural characteristics and the level and rate of change in stress observed in each population. METHOD: The stress trajectories of mothers of young children with Down syndrome (n = 25) and a mixed-aetiology comparison group (n = 49) were estimated, using growth modelling on data collected at ages of 15, 30 and 45 months. RESULTS: On average, stress in the mixed comparison group was higher at Time 1 and remained unchanged over time, while stress in the Down syndrome group was lower at Time 1 but increased steadily. After taking diagnostic group membership into account, more advanced cognitive-linguistic functioning and lower levels of maladaptive behaviours at all time points were associated with lower levels of maternal stress. CONCLUSIONS; These findings suggest that the cognitive-linguistic and behavioural trajectory observed in early development in Down syndrome may contribute to the changes in maternal stress levels observed throughout these early years. Implications for developing targeted and time- sensitive family interventions for families of children with Down syndrome are discussed.

Macrocephaly in autism and other pervasive developmental disorders.

To assess the prevalence of macrocephaly (head circumference > or = 1.88 standard deviations above normative data for age and sex or > 97th centile) in autism and other pervasive developmental disorders, 41 children with autism, and a comparison group of 21 children with tuberous sclerosis complex (TSC) or an unspecified seizure disorder were studied. Familiality of head circumference was also assessed from measurements of 133 first-degree relatives. Significantly higher rates of macrocephaly were found in probands with autism (12.2%) and their first-degree relatives (15.5%) when compared against a published normative sample. The incidence of macrocephaly in the comparison group of probands with TSC and seizure disorder (9.5%) and their first-degree relatives (8.3%) was higher than normative data as well, although the relation between macrocephaly and autism was more pronounced. Head circumference and extreme scores reflecting macrocephaly were moderately heritable in the present sample (H2 = 0.47). The increased prevalence of macrocephaly in relatives of children with autism compared with control children suggests that this characteristic may be a familial risk factor in the pathogenesis of autism.

Craniofacial maturity and perceived personality in children with Down syndrome.

In this pair of studies, we examined whether the common perception of a positive Down syndrome personality is associated with a youthful craniofacial appearance, similar to Zebrowitz's (1997) "babyface." In Study 1, 43 observers rated photographs of age-matched children with Down syndrome, another mental retardation syndrome (5p- syndrome), and typically developing children. Those with Down syndrome were perceived as being more physically babyfaced and more likely to behave in an immature manner. We controlled for the effect of familiarity with Down syndrome in Study 2 by employing a within-etiology design in which 128 observers rated 12 pictures of 10-year-old children with Down syndrome. Results showed that more physically babyfaced children with Down syndrome are more subject to the overgeneralization.

Stress and coping in families of children with Smith-Magenis syndrome.

To describe stress and coping in families of children with Smith-Magenis syndrome, the present authors interviewed and received questionnaires from families of 36 children with this disorder. For measures of total stress, and of parent and family problems, the best predictors were the family's number of friends and the child's degree of impairment on the Vineland socialization domain; the single best predictor of parental pessimism was the child's degree of maladaptive behaviour. Although the stress levels of the families of children with Smith-Magenis syndrome are comparable to the levels shown by the families of children with Prader-Willi and 5p- syndromes, these levels are much higher than the stress levels reported by families of children with mixed or non-specific developmental disabilities. Stress levels may be similar across aetiologies involving high levels of maladaptive behaviour, but the correlates of family stress--particularly the moderating role of family friends--seem specific to Smith-Magenis syndrome.