Goffredina Spanò

Obstructive sleep apnea syndrome and cognition in Down syndrome

Good‐quality sleep is essential for normal learning and memory. Sleep fragmentation and disrupted sleep architecture are commonly observed throughout the lifespan of individuals with Down syndrome, a condition marked by cognitive deficits emerging within the first few months of life. While obstructive sleep apnea syndrome (OSAS) is known to contribute to the loss of sleep quality in Down syndrome, its relation to cognitive and behavioral impairment remains poorly understood.

The impact of sleep disruption on executive function in Down syndrome

The high prevalence of sleep disorders, particularly obstructive sleep apnea, is well established in children with Down syndrome. However, only a few studies have focused on older children and young adults in this population. Given the presence of sleep disorders and the early emergence of Alzheimers disease, more work is needed to examine the relationship between sleep and cognition in Down syndrome. Twenty-nine adolescents and young adults with Down syndrome participated in the present study. Parents reported on their sleep difficulties using a well-validated measure of sleep problems in intellectual disabilities. Based on theoretical models linking obstructive sleep apnea to prefrontal cortex dysfunction, we tested components of executive functions that have been shown to be impaired in previous studies of Down syndrome. First, results indicate that participants with Down syndrome with higher body mass index also had increased caregiver reports of sleep apnea symptoms. Individuals with high ratings of sleep disruption also showed greater difficulties with executive function. These results suggest that sleep disruption may place this set of functions at risk in young adults. Future work should examine if this risk may result in earlier onset of dementia or steeper decline with Alzheimers disease. Further, additional studies are needed to investigate the effect of exercise interventions and weight reduction on sleep disorders in this population.

Human and mouse model cognitive phenotypes in Down syndrome: implications for assessment

The study of cognitive function in Down syndrome (DS) has advanced rapidly in the past decade. Mouse models have generated data regarding the neurological basis for the specific cognitive profile of DS (i.e., deficits in aspects of hippocampal, prefrontal, and cerebellar function) and have uncovered pharmacological treatments with the potential to affect this phenotype. Given this progress, the field is at a juncture in which we require assessments that may effectively translate the findings acquired in mouse models to humans with DS. In this chapter, we describe the cognitive profile of humans with DS and associated mouse models, discussing the ways in which we may merge these findings so as to more fully understand cognitive strengths and weaknesses in this population. New directions for approaches to cognitive assessment in mice and humans are discussed.

Human and mouse model cognitive phenotypes in Down syndrome

The study of cognitive function in Down syndrome (DS) has advanced rapidly in the past decade. Mouse models have generated data regarding the neurological basis for the specific cognitive profile of DS (i.e., deficits in aspects of hippocampal, prefrontal, and cerebellar function) and have uncovered pharmacological treatments with the potential to affect this phenotype. Given this progress, the field is at a juncture in which we require assessments that may effectively translate the findings acquired in mouse models to humans with DS. In this chapter, we describe the cognitive profile of humans with DS and associated mouse models, discussing the ways in which we may merge these findings so as to more fully understand cognitive strengths and weaknesses in this population. New directions for approaches to cognitive assessment in mice and humans are discussed.

Sleep Disturbance and Expressive Language Development in Preschool-Age Children With Down Syndrome

Recent evidence has suggested that sleep may facilitate language learning. This study examined variation in language ability in 29 toddlers with Down syndrome (DS) in relation to levels of sleep disruption. Toddlers with DS and poor sleep (66%, n = 19) showed greater deficits on parent-reported and objective measures of language, including vocabulary and syntax. Correlations between sleep and language were found in groups with equivalent medical and social backgrounds and after control for relevant behavioral comorbidities, including autism symptoms. These results emphasize the important role of quality sleep in all childrens expressive language development, and may help increase our understanding of the etiology of language deficits in developmental disorders, potentially leading to new treatment approaches.

Neuropsychological effects of second language exposure in Down syndrome

BACKGROUND While it has been common practice to discourage second language learning in neurodevelopmental disorders involving language impairment, little is known about the effects of second language exposure (SLE) on broader cognitive function in these children. Past studies have not found differences on language tasks in children with Down syndrome (DS) and SLE. We expand on this work to determine the effects on the broader cognitive profile, including tests tapping deficits on neuropsychological measures of prefrontal and hippocampal function. METHOD This study examined the specific cognitive effects of SLE in children with DS (aged 7-18 years). Children with SLE (n = 13: SLE predominantly Spanish) and children from monolingual homes (n = 28) were assessed on a standardised battery of neuropsychological tests developed for DS, the Arizona Cognitive Test Battery. The current exposure level to a language other than English in the SLE group was greater than 4 h per day on average. RESULTS No group differences were observed for any outcome, and level of exposure was also not linearly related to neuropsychological outcomes, several of which have been shown to be impaired in past work. CONCLUSION There were no measurable effects of SLE on neuropsychological function in this sample of children with DS. Potential clinical implications of these findings are discussed.

Seeing Can Be Remembering Interactions Between Memory and Perception in Typical and Atypical Development

Recent work suggests that memory representations may guide basic perceptual functions, such as figure-ground perception. In three studies we assessed top-down contributions to figure-ground perception in typical development and in two developmental disorders: Down syndrome (DS) and autism (ASD). We investigated how figure-ground segregation is modulated by high-level cues (i.e., memory representations) and low-level cues (i.e., convexity and surface integration). Study 1 results showed that both high-level and low-level contributions to figure-ground perception are functional by the age of 4 years. In Study 2, individuals with DS exhibited intact figure-ground segregation based on low level cues when compared with mental age–matched participants, but they showed attenuated effects of high-level memory cues on figure-ground assignment. In Study 3, individuals with ASD showed intact effects of both high-level and low-level cues on figure-ground perception, counter to previous suggestions that high-level influences on perception are usually impaired in ASD.

Symptoms of Attention-Deficit/Hyperactivity Disorder in Down Syndrome: Effects of the Dopamine Receptor D4 Gene

This study examined individual differences in ADHD symptoms and executive function (EF) in children with Down syndrome (DS) in relation to the dopamine receptor D4 (DRD4) gene, a gene often linked to ADHD in people without DS. Participants included 68 individuals with DS (7-21 years), assessed through laboratory tasks, caregiver reports, and experimenter ratings. Saliva samples were collected from the DS group and 66 children without DS to compare DRD4 allele distribution, showing no difference between the groups. When the sample with DS was stratified for ethnicity (n  =  32), the DRD4 7-repeat allele significantly related to parent and experimenter ratings, but not to laboratory assessments. These results suggest that nontrisomy genetic factors may contribute to individual differences in ADHD symptoms in persons with DS.

Young children with Down syndrome show normal development of circadian rhythms, but poor sleep efficiency: a cross-sectional study across the first 60 months of life

Objectives To evaluate sleep consolidation and circadian activity rhythms in infants and toddlers with Down syndrome (DS) under light and socially entrained conditions within a familiar setting. Given previous human and animal data suggesting intact circadian regulation of melatonin across the day and night, it was hypothesized that behavioral indices of circadian rhythmicity would likewise be intact in the sample with DS. Methods A cross-sectional study of 66 infants and young children with DS, aged 5–67 months, and 43 typically developing age-matched controls. Sleep and measures of circadian robustness or timing were quantified using continuous in-home actigraphy recordings performed over seven days. Circadian robustness was quantified via time series analysis of rest-activity patterns. Phase markers of circadian timing were calculated alongside these values. Sleep efficiency was also estimated based on the actigraphy recordings. Results This study provided further evidence that general sleep quality is poor in infants and toddlers with DS, a population that has sleep apnea prevalence as high as 50% during the preschool years. Despite poor sleep quality, circadian rhythm and phase were preserved in children with DS and displayed similar developmental trajectories in cross-sectional comparisons with a typically developing (TD) cohort. In line with past work, lower sleep efficiency scores were quantified in the group with DS relative to TD children. Infants born with DS exhibited the worst sleep fragmentation; however, in both groups, sleep efficiency and consolidation increased across age. Three circadian phase markers showed that 35% of the recruitment sample with DS was phase-advanced to an earlier morning schedule, suggesting significant within-group variability in the timing of their daily activity rhythms. Conclusions Circadian rhythms of wake and sleep are robust in children born with DS. The present results suggest that sleep fragmentation and any resultant cognitive deficits are likely not confounded by corresponding deficits in circadian rhythms.

Everyday memory in individuals with Down syndrome: Validation of the Observer Memory Questionnaire - Parent Form.

ABSTRACT The memory profile of individuals with Down syndrome (DS) has mainly been examined through traditional laboratory tasks, often revealing substantial deficits in episodic and declarative memory. Little is known about the relation between memory abilities as measured in the laboratory versus naturalistic settings in this population, and no questionnaire assessments of everyday memory have been formally validated for this group. The current study’s aims were twofold: 1) to describe the psychometric characteristics of a parent-reported everyday memory measure (the Observer Memory Questionnaire – Parent Form, OMQ-PF) in this population with known hippocampal and memory impairment (i.e., DS, ages 7–35 years), and 2) to determine if the measure has the sensitivity to detect impairments, thus providing some of the first data to document parent reports of everyday memory in individuals with DS. The results indicate that this scale is a reliable instrument for detecting and tracking memory deficits over time in this population. We found a correlation between parent reports of everyday memory difficulties and well-replicated deficits in a laboratory-based memory task (i.e., place–object paired associates learning). Our results suggest that the OMQ-PF has the potential to be used as a tool to help to track the status of memory function in this group both for use in descriptive studies and in studies of behavior and pharmacological intervention.