Memory profiles in Down syndrome across development: a review of memory abilities through the lifespan

Associations Among Sex, Cognitive Ability, and Autism Symptoms in Individuals with Down Syndrome

This study explores sex-differences in (a) rates and profiles of autism symptoms as well as in (b) the contribution of intellectual quotient (IQ) to autism symptom presentation in Down syndrome (DS). Participants were 40 males and 38 females with DS, aged 6 to 23 years. Autism symptoms were rated through the Autism Diagnostic Observation Schedule-Second Edition (ADOS-2). Results show no sex differences in the ADOS-2 Calibrated Severity Scores (CSS). However, only females with DS who are classified as DS-Only have higher scores on verbal IQ than those classified as DS + autism. Furthermore, associations between IQ and all CSSs are found for females, but not for males. Findings suggest that verbal cognition may play differential roles for females and males with DS.

Extended trajectory of spatial memory errors in typical and atypical development: The role of binding and precision

Spatial reconstruction, a method for evaluating how individuals remember the placement of objects, has traditionally been evaluated through the aggregate estimation of placement errors. However, this approach may obscure the nature of task errors. Specifically, recent data has suggested the importance of examining the precision of responses, as well as absolute performance on item-context bindings. In contrast to traditional analysis approaches based on the distance between the target and the reconstructed item, in this study we further explored three types of errors (swap error, global error, and local distance) that may all contribute to the distance, with particular emphasis on swap errors and local distance due to their associations with item-context bindings and memory precision, respectively. We examined these errors in children aged 3-18 years, making comparisons between children with typical development (TD) and children with Down syndrome (DS), a population with known memory challenges. As expected, older children outperformed younger children in terms of overall memory accuracy. Of importance is that we measured uneven maturational trajectories of memory abilities across the various error types. Specifically, both remembered locations (irrespective of object identity) and swap errors (object-location binding errors) align with the overall memory accuracy. Memory precision, as measured by local distance in simpler set size 2 trials, mirrored overall memory accuracy. However, for more complex set size 3 trials, local distance remained stable before age 8 and showed age-related change thereafter. The group with DS showed reduced precision compared to a TD matched group, and measures of precision, and to a lesser extent binding errors, correlated with standard neuropsychological outcomes. Overall, our study contributed to a fine-grained understanding of developing spatial memory ability in a large sample of typical developing children and a memory impaired population. These findings contribute to a growing body of research examining precision as a key factor in memory performance.

Distinct neuroanatomical and neuropsychological features of Down syndrome compared to related neurodevelopmental disorders: a systematic review

Objectives

We critically review research findings on the unique changes in brain structure and cognitive function characteristic of Down syndrome (DS) and summarize the similarities and differences with other neurodevelopmental disorders such as Williams syndrome, 22q11.2 deletion syndrome, and fragile X syndrome.

Methods

We conducted a meta-analysis and systematic literature review of 84 studies identified by searching PubMed, Google Scholar, and Web of Science from 1977 to October 2022. This review focuses on the following issues: (1) specific neuroanatomic and histopathological features of DS as revealed by autopsy and modern neuroimaging modalities, (2) language and memory deficits in DS, (3) the relationships between these neuroanatomical and neuropsychological features, and (4) neuroanatomic and neuropsychological differences between DS and related neurodevelopmental syndromes.

Results

Numerous post-mortem and morphometric neuroimaging investigations of individuals with DS have reported complex changes in regional brain volumes, most notably in the hippocampal formation, temporal lobe, frontal lobe, parietal lobe, and cerebellum. Moreover, neuropsychological assessments have revealed deficits in language development, emotional regulation, and memory that reflect these structural changes and are more severe than expected from general cognitive dysfunction. Individuals with DS also show relative preservation of multiple cognitive, linguistic, and social domains compared to normally developed controls and individuals with other neurodevelopmental disorders. However, all these neurodevelopment disorders exhibit substantial heterogeneity among individuals.

Conclusion

People with Down syndrome demonstrate unique neurodevelopmental abnormalities but cannot be regarded as a homogenous group. A comprehensive evaluation of individual intellectual skills is essential for all individuals with neurodevelopment disorders to develop personalized care programs.

Single-Nucleus Profiling Identifies Accelerated Oligodendrocyte Precursor Cell Senescence in a Mouse Model of Down Syndrome

Down syndrome (DS), the most common genetic cause of intellectual disability, is associated with lifelong cognitive deficits. However, the mechanisms by which triplication of chromosome 21 genes drive neuroinflammation and cognitive dysfunction are poorly understood. Here, using the Ts65Dn mouse model of DS, we performed an integrated single-nucleus ATAC and RNA-sequencing (snATAC-seq and snRNA-seq) analysis of the adult cortex. We identified cell type-specific transcriptional and chromatin-associated changes in the Ts65Dn cortex, including regulators of neuroinflammation, transcription and translation, myelination, and mitochondrial function. We discovered enrichment of a senescence-associated transcriptional signature in Ts65Dn oligodendrocyte (OL) precursor cells (OPCs) and epigenetic changes consistent with a loss of heterochromatin. We found that senescence is restricted to a subset of OPCs concentrated in deep cortical layers. Treatment of Ts65Dn mice with a senescence-reducing flavonoid rescued cortical OPC proliferation, restored microglial homeostasis, and improved contextual fear memory. Together, these findings suggest that cortical OPC senescence may be an important driver of neuropathology in DS.

The co-construction of a reading assessment measure with adults with Down syndrome: a meaningful literacy approach

Introduction

The need to develop appropriate measures of broad-based reading-related literacy skills for adults with Down syndrome has been highlighted in the literature. In this study we aimed to co-construct a valid and reliable assessment measure that can be used to document meaningful everyday reading, in adolescents and adults with Down syndrome.

Methods

The study was carried out in two stages. Stage 1 used an inclusive participatory design in which individuals with Down syndrome were research collaborators (n = 46). Items to be included in the measure were identified and ecological, face and content validity were established through an iterative process. In stage 2 we examined the reliability of the tool and explored potential relationships between meaningful reading score and (1) age, (2) receptive vocabulary, and (3) reading ability as measured by standardized assessments. In addition, we profiled what a pilot cohort of adults with Down syndrome read (n = 33) and how they experience reading in their everyday lives.

Results

Results showed that 46 items were generated for inclusion in the Meaningful Reading Measure (MRM). Our preliminary data showed that the tool has internal and external reliability and ecological and content validity. There were no associations between meaningful reading score and any of the other variables examined. There was considerable variability in items read (range 12-44) which reflected a broad range of reading practices. Adults with Down syndrome identified the importance of reading as a pleasurable activity and as something that aids learning.

Conclusion

The MRM developed here can be used (1) as a reading intervention outcome measure to complement existing standardized tools, (2) to profile meaningful reading in adults with Down syndrome, (3) to guide reading module content, and (4) to capture change in adults' perceptions of themselves as readers. Future work is needed to establish the tool's sensitivity to change over time.

Evaluation of a smart home platform for adults with Down syndrome

People with Down syndrome (DS) encounter difficulties in their daily lives. In recent years, smart homes have provided some answers to the problem of residential autonomy. In fact, smart homes can provide support for complex routines and activities, while adjusting to the person's behaviors and needs and offering maximum control of the environment. In this context, the objectives of this study were to assess (i) the usability of the smart home platform as well as (ii) the impact of the use (for 6 months) of this platform by adults with DS on many dimensions such as residential autonomy, projection into the future, the development of a life plan, self-determination, quality of life, self-esteem, anxiety, and psychological well-being. The first objective of a preliminary study was to verify that the support platform we use is suitable and can be used effectively by people with DS. For the preliminary study, the evaluations show effective, satisfactory and efficient use of all applications. Regarding the objective of our study, the evaluations show positive impacts on many dimensions such as living skills, self-determination, quality of life, self-esteem, anxiety and certain components of life psychological well-being.

Morphosyntactic development in German-speaking individuals with Down syndrome-longitudinal data

Introduction

The present study provides longitudinal data on the development of receptive and expressive grammar in children and adolescents with Down syndrome and addresses the role of nonverbal cognitive abilities and verbal short-term memory for morphosyntactic development.

Method

Seventeen German-speaking individuals with Down syndrome (aged 4;6-17;1 years at first testing (T1)) were assessed twice, 4;4-6;6 years apart. For a subset of five participants, there was also a third assessment 2 years after the second. Receptive grammar, nonverbal cognition, and verbal short-term memory were tested using standardized measures. For expressive grammar, elicitation tasks were used to assess the production of subject-verb agreement and of wh-questions.

Results

At group level, the participants showed a significant increase in grammar comprehension from T1 to T2. However, progress diminished with increasing chronological age. Notable growth could not be observed beyond the age of 10 years.With respect to expressive grammatical abilities, progress was limited to those participants who had mastered verbal agreement inflection around age 10 years. Individuals who did not master verbal agreement by late childhood achieved no progress in producing wh-questions, either.There was an increase in nonverbal cognitive abilities in the majority of participants. Results for verbal short-term memory followed a similar pattern as those for grammar comprehension. Finally, neither nonverbal cognition nor verbal short-term memory were related to changes in receptive or expressive grammar.

Discussion

The results point to a slowdown in the acquisition of receptive grammar which starts before the teenage years. For expressive grammar, improvement in wh-question production only occurred in individuals with good performance in subject-verb agreement marking, which suggests that the latter might have a trigger function for further grammatical development in German-speaking individuals with Down syndrome. The study provides no indication that nonverbal cognitive abilities or verbal short-term memory performance determined the receptive or expressive development. The results lead to clinical implications for language therapy.

From neurodevelopment to neurodegeneration: utilizing human stem cell models to gain insight into Down syndrome

Down syndrome (DS), caused by triplication of chromosome 21, is the most frequent aneuploidy observed in the human population and represents the most common genetic form of intellectual disability and early-onset Alzheimer's disease (AD). Individuals with DS exhibit a wide spectrum of clinical presentation, with a number of organs implicated including the neurological, immune, musculoskeletal, cardiac, and gastrointestinal systems. Decades of DS research have illuminated our understanding of the disorder, however many of the features that limit quality of life and independence of individuals with DS, including intellectual disability and early-onset dementia, remain poorly understood. This lack of knowledge of the cellular and molecular mechanisms leading to neurological features of DS has caused significant roadblocks in developing effective therapeutic strategies to improve quality of life for individuals with DS. Recent technological advances in human stem cell culture methods, genome editing approaches, and single-cell transcriptomics have provided paradigm-shifting insights into complex neurological diseases such as DS. Here, we review novel neurological disease modeling approaches, how they have been used to study DS, and what questions might be addressed in the future using these innovative tools.

Brain reserve theory: Are adults with intellectual disability more vulnerable to age than peers with typical development?

BACKGROUND

Life expectancy is on rise and the intriguing question is: When does cognitive decline occur among adults with intellectual disability, compared to adults with typical development? This cross-sectional study examined cognitive performance of crystallised/fluid intelligence, working and long-term memory of adults with intellectual disability of etiologies other than Down syndrome (IQ 50-68) and adults with typical development (IQ 85-114) in four age cohorts (30-39; 40-49; 50-59; 60-69).

METHOD

The WAIS III^HEB and the Rey-AVLT were administered to both groups.

RESULTS

Four patterns of cognitive performance were found: (a) Vocabulary (crystallised intelligence), Spatial Span Forward and Retention yielded similar scores across all four age cohorts in participants with typical development and with intellectual disability. (b) Similarities, Raven and Digit Span Backward exhibit lower scores only in 50-59 or 60-69 compared to the 30-39 age cohort in both groups, (c) Digit Span Forward, Spatial Span Backward and Total Leaning (LTM) yielded lower scores in the 50-59 or 60-69 age cohorts in the typical group, but similar scores in participants with intellectual disability along the age cohorts, (d) Block Design (fluid intelligence) yielded a lower score in the 50-59 cohort versus lower scores only at ages 60-69 in participants with typical development.

CONCLUSIONS

Our findings suggest a possible parallel trajectory in age-related cognitive performance for individuals with and without intellectual disability in six measures, and a possible more preserved trajectory in fluid intelligence and some memory measures in adults with intellectual disability compared to their peers. Caution should be exercised regarding Digit and Spatial Span Backwards, which yielded a floor effect in participants with intellectual disability. The Cognitive Reserve Theory, the Safeguard Hypothesis and late maturation might serve as explanations for these findings.

The Conserved Transcriptional Activation Activity Identified in Dual-Specificity Tyrosine-(Y)-Phosphorylation-Regulated Kinase 1

Dual-specificity tyrosine-(Y)-phosphorylation-regulated kinase 1 (DYRK1) encodes a conserved protein kinase that is indispensable to neuron development. However, whether DYRK1 possesses additional functions apart from kinase function remains poorly understood. In this study, we firstly demonstrated that the C-terminal of ascidian Ciona robusta DYRK1 (CrDYRK1) showed transcriptional activation activity independent of its kinase function. The transcriptional activation activity of CrDYRK1 could be autoinhibited by a repression domain in the N-terminal. More excitingly, both activation and repression domains were retained in HsDYRK1A in humans. The genes, activated by the activation domain of HsDYRK1A, are mainly involved in ion transport and neuroactive ligand-receptor interaction. We further found that numerous mutation sites relevant to the DYRK1A-related intellectual disability syndrome locate in the C-terminal of HsDYRK1A. Then, we identified several specific DNA motifs in the transcriptional regulation region of those activated genes. Taken together, we identified a conserved transcription activation domain in DYRK1 in urochordates and vertebrates. The activation is independent of the kinase activity of DYRK1 and can be repressed by its own N-terminal. Transcriptome and mutation data indicate that the transcriptional activation ability of HsDYRK1A is potentially involved in synaptic transmission and neuronal function related to the intellectual disability syndrome.

Single-cell sequencing: promises and challenges for human genetics

Over the last decade, single-cell sequencing has transformed many fields. It has enabled the unbiased molecular phenotyping of even whole organisms with unprecedented cellular resolution. In the field of human genetics, where the phenotypic consequences of genetic and epigenetic alterations are of central concern, this transformative technology promises to functionally annotate every region in the human genome and all possible variants within them at a massive scale. In this review aimed at the clinicians in human genetics, we describe the current status of the field of single-cell sequencing and its role for human genetics, including how the technology works as well as how it is being applied to characterize and monitor diseases, to develop human cell atlases, and to annotate the genome.

Integrating familiar listeners and speech recognition technologies into augmentative and alternative communication intervention for adults with down syndrome: Descriptive exploration

Many individuals with Down syndrome exhibit speech impairments that necessitate augmentative and alternative communication (AAC) intervention. AAC intervention allows for access to communication through means other than, or supplemental to, speech. This descriptive study provided initial insight into the feasibility of incorporating familiar listeners (e.g., family members) and speech recognition technology into AAC intervention to increase communication success for individuals with Down syndrome. Six adults with Down syndrome participated. The participants' intelligibility to a familiar listener, unfamiliar listeners, and speech recognition technologies (i.e., Google Speech-to-Text and Windows Speech Recognition) was evaluated. Additionally, consistency in word pronunciation was evaluated to examine the feasibility of future training of speech recognition technologies. The participating adults with Down syndrome experienced limited intelligibility to all listeners and technologies but were most intelligible to familiar listeners. The adults also demonstrated consistencies across their production of words, and across one another's productions. The findings suggest the promise in using familiar listeners as a current resource and speech recognition technology as a future resource in AAC intervention for adults with Down syndrome. However, intervention research and technological development are needed to thoroughly explore these approaches.

Astroglial and microglial pathology in Down syndrome: Focus on Alzheimer's disease

Down syndrome (DS) arises from the triplication of human chromosome 21 and is considered the most common genetic cause of intellectual disability. Glial cells, specifically astroglia and microglia, display pathological alterations that might contribute to DS neuropathological alterations. Further, in middle adulthood, people with DS develop clinical symptoms associated with premature aging and Alzheimer's disease (AD). Overexpression of the amyloid precursor protein (APP) gene, encoded on chromosome 21, leads to increased amyloid-β (Aβ) levels and subsequent formation of Aβ plaques in the brains of individuals with DS. Amyloid-β deposition might contribute to astroglial and microglial reactivity, leading to neurotoxic effects and elevated secretion of inflammatory mediators. This review discusses evidence of astroglial and microglial alterations that might be associated with the AD continuum in DS.

Prospective memory in adults with down syndrome

Prospective memory (PM) refers to the ability to remember one's intentions (what I must do), at the appropriate time, in the future (when I must do it). The objective of this work is to study the performance of people with Down syndrome (DS) compared to two control groups, matched by mental age and chronological age. For this purpose, an adapted version of the virtual week, which is an ecological test to simulate the functioning of PM in everyday life, was used. The results suggest that people with DS have difficulties in PM that mainly concern the binding (association) between prospective (when to do) and retrospective (what to do) components. Moreover, people with DS perform better in PM when the task is repeated and time-based. These results are discussed in light of studies conducted with other populations.

Cognitive outcome measures for tracking Alzheimer's disease in Down syndrome

Down syndrome (DS) is now viewed as a genetic type of Alzheimer's disease (AD), given the near-universal presence of AD pathology in middle adulthood and the elevated risk for developing clinical AD in DS. As the field of DS prepares for AD clinical intervention trials, there is a strong need to identify cognitive measures that are specific and sensitive to the transition from being cognitively stable to the prodromal (e.g., Mild Cognitive Impairment-Down syndrome) and clinical AD (e.g., Dementia) stages of the disease in DS. It is also important to determine cognitive measures that map onto biomarkers of early AD pathology during the transition from the preclinical to the prodromal stage of the disease, as this transition period is likely to be targeted and tracked in AD clinical trials. The present chapter discusses the current state of research on cognitive measures that could be used to screen/select study participants and as potential outcome measures in future AD clinical trials with adults with DS. In this chapter, we also identify key challenges that need to be overcome and questions that need to be addressed by the DS field as it prepares for AD clinical trials in the coming years.

Neurodevelopment in Down syndrome: Concordance in humans and models

Great strides have been made over the past 30 years in understanding the neurodevelopmental changes underlying the intellectual disability (ID) in Down syndrome (DS). Detailed studies of human tissue coupled with findings from rodent and induced pluripotent stem cells (iPSCs) model systems have uncovered the changes in neurogenesis, synaptic connectivity, and myelination that drive the anatomical and physiological changes resulting in the disability. However, there remain significant conflicting data between human studies and the models. To fully understand the development of ID in DS, these inconsistencies need to be reconciled. Here, we review the well documented neurodevelopmental phenotypes found in individuals with DS and examine the degree to which widely used models recapitulate these phenotypes. Resolving these areas of discord will further research on the molecular underpinnings and identify potential treatments to improve the independence and quality of life of people with DS.

The innate immune system stimulating cytokine GM-CSF improves learning/memory and interneuron and astrocyte brain pathology in Dp16 Down syndrome mice and improves learning/memory in wild-type mice

Down syndrome (DS) is characterized by chronic neuroinflammation, peripheral inflammation, astrogliosis, imbalanced excitatory/inhibitory neuronal function, and cognitive deficits in both humans and mouse models. Suppression of inflammation has been proposed as a therapeutic approach to treating DS co-morbidities, including intellectual disability (DS/ID). Conversely, we discovered previously that treatment with the innate immune system stimulating cytokine granulocyte-macrophage colony-stimulating factor (GM-CSF), which has both pro- and anti-inflammatory activities, improved cognition and reduced brain pathology in a mouse model of Alzheimer's disease (AD), another inflammatory disorder, and improved cognition and reduced biomarkers of brain pathology in a phase II trial of humans with mild-to-moderate AD. To investigate the effects of GM-CSF treatment on DS/ID in the absence of AD, we assessed behavior and brain pathology in 12-14 month-old DS mice (Dp[16]1Yey) and their wild-type (WT) littermates, neither of which develop amyloid, and found that subcutaneous GM-CSF treatment (5 μg/day, five days/week, for five weeks) improved performance in the radial arm water maze in both Dp16 and WT mice compared to placebo. Dp16 mice also showed abnormal astrocyte morphology, increased percent area of GFAP staining in the hippocampus, clustering of astrocytes in the hippocampus, and reduced numbers of calretinin-positive interneurons in the entorhinal cortex and subiculum, and all of these brain pathologies were improved by GM-CSF treatment. These findings suggest that stimulating and/or modulating inflammation and the innate immune system with GM-CSF treatment may enhance cognition in both people with DS/ID and in the typical aging population.

Neurogenesis and neuronal differentiation in the postnatal frontal cortex in Down syndrome

Although Down syndrome (DS), the most common developmental genetic cause of intellectual disability, displays proliferation and migration deficits in the prenatal frontal cortex (FC), a knowledge gap exists on the effects of trisomy 21 upon postnatal cortical development. Here, we examined cortical neurogenesis and differentiation in the FC supragranular (SG, II/III) and infragranular (IG, V/VI) layers applying antibodies to doublecortin (DCX), non-phosphorylated heavy-molecular neurofilament protein (NHF, SMI-32), calbindin D-28K (Calb), calretinin (Calr), and parvalbumin (Parv), as well as β-amyloid (APP/Aβ and Aβ_1-42) and phospho-tau (CP13 and PHF-1) in autopsy tissue from age-matched DS and neurotypical (NTD) subjects ranging from 28-weeks (wk)-gestation to 3 years of age. Thionin, which stains Nissl substance, revealed disorganized cortical cellular lamination including a delayed appearance of pyramidal cells until 44 wk of age in DS compared to 28 wk in NTD. SG and IG DCX-immunoreactive (-ir) cells were only visualized in the youngest cases until 83 wk in NTD and 57 wk DS. Strong SMI-32 immunoreactivity was observed in layers III and V pyramidal cells in the oldest NTD and DS cases with few appearing as early as 28 wk of age in layer V in NTD. Small Calb-ir interneurons were seen in younger NTD and DS cases compared to Calb-ir pyramidal cells in older subjects. Overall, a greater number of Calb-ir cells were detected in NTD, however, the number of Calr-ir cells were comparable between groups. Diffuse APP/Aβ immunoreactivity was found at all ages in both groups. Few young cases from both groups presented non-neuronal granular CP13 immunoreactivity in layer I. Stronger correlations between brain weight, age, thionin, DCX, and SMI-32 counts were found in NTD. These findings suggest that trisomy 21 affects postnatal FC lamination, neuronal migration/neurogenesis and differentiation of projection neurons and interneurons that likely contribute to cognitive impairment in DS.

Caught in the ACTS: Defining Abstract Cognitive Task Sequences as an Independent Process

Cognitive neuroscience currently conflates the study of serial responses (e.g., delay match to sample/nonsample, n-back) with the study of sequential operations. In this essay, our goal is to define and disentangle the latter, termed abstract cognitive task sequences (ACTS). Existing literatures address tasks requiring serial events, including procedural learning of implicit motor responses, statistical learning of predictive relationships, and judgments of attributes. These findings do not describe the behavior and underlying mechanism required to succeed at remembering to evaluate color, then shape; or to multiply, then add. A new literature is needed to characterize these sorts of second-order cognitive demands of studying a sequence of operations. Our second goal is to characterize gaps in knowledge related to ACTS that merit further investigation. In the following sections, we define more precisely what we mean by ACTS and suggest research questions' further investigation would be positioned to address.

An Investigation of Working Memory Profile and Fluid Intelligence in Children With Neurodevelopmental Difficulties

The present study aims to evaluate the distinct patterns of working memory (WM) capacity of children with Developmental Language Disorder (DLD), High-functioning children with Autism Spectrum Disorder (ASD) and children with Down syndrome (DS). More specifically, the current study investigates the complex relationship of fluid intelligence and WM between 39 children with DLD, 20 H igh-functioning children with ASD, and 15 children with DS. All children were evaluated in different measures of Phonological Working Memory, Visual-spatial Working Memory whereas Fluid Intelligence was measured with Raven Progressive Matrices. The result analysis revealed a significant difference among the three groups, both among each function separately and the correlations among them, as well. The results revealed that the DLD groups and High-functioning ASD group exhibited a common picture or an overlap of performances in all Phonological and Visuo-spatial working memory measures, except Backward Digit Recall task. As for the DS group research findings revealed different and unique working memory patterns in comparison to DLD group and High-functioning ASD. Their differences have been studied and further conclusions have been drawn about the different patterns of working memory among the three clinical groups. The implications of these findings are discussed in light of support for learning. The common profile that characterize the two developmental conditions and the distinct pattern of working memory performance in DS group underlies the need for further research in the field.

Short-term memory outcome measures: Psychometric evaluation and performance in youth with Down syndrome

BACKGROUND

Improving short-term memory (STM) performance for individuals with Down syndrome (DS) has been a target of recent clinical trials. Validation of STM outcome measures is essential for research rigor in trials among children and adolescents with DS.

AIMS

The current study investigated the psychometric properties of four direct STM assessments and one everyday memory parent form.

METHODS AND PROCEDURES

Measures were administered to a sample of 74 youth with DS at two visits, two weeks apart. Overall cognitive abilities were also assessed.

OUTCOMES AND RESULTS

The OMQ-PF had good feasibility and distribution of scores, but floor effects were prominent for direct measures. Test-retest reliability was poor to moderate for all measures and practice effects were problematic for the NEPSY-II List Memory and DAS-II Recall of Objects subtests. Commonalities in responses were observed, including primacy/recency effects, and some STM scores were correlated with overall cognitive abilities.

CONCLUSIONS AND IMPLICATIONS

The OMQ-PF met most study criteria, but no direct measure met sufficient criteria to be strongly recommended for future clinical trials. Because higher cognitive abilities were related to assessment completion, STM measures may require adaptation for use in broader samples of youth with DS across all levels of cognitive ability.

Language and executive functioning in young adults with Down syndrome

BACKGROUND

This study examined the association between executive functioning and language in young adults with Down syndrome (DS).

METHOD

Nineteen young adults with DS (aged 19-24 years) completed standardised measures of overall cognition, vocabulary, verbal fluency and executive function skills.

RESULTS

Friedman's analysis of variance (χ² (3) = 28.15, P < .001) and post hoc comparisons indicated that, on average, participants had a significantly lower overall non-verbal than verbal cognitive age equivalent and lower expressive than receptive vocabulary skills. Using Spearman correlations, performance on a verbal measure of cognition inhibition was significantly negatively related to receptive vocabulary (ρ = -.529, adjusted P = .036) and verbal fluency (ρ = -.608, adjusted P = .022). Attention was significantly positively correlated with receptive (ρ = .698, adjusted-p = .005) and expressive (ρ = .542, adjusted P = .027) vocabulary. Verbal working memory was significantly positively associated with receptive vocabulary (ρ = .585, adjusted P = .022) and verbal fluency (ρ = .737, adjusted P = .003). Finally, visuospatial working memory was significantly associated with receptive vocabulary (ρ = .562, adjusted P = .027).

CONCLUSIONS

Verbal and non-verbal measures of executive functioning skills had important associations with language ability in young adults with DS. Future translational research is needed to investigate causal pathways underlying these relationships. Research should explore if interventions aimed at increasing executive functioning skills (e.g. attention, inhibition and working memory) have the potential to lead to increases in language for young adults with DS.

Altered cell and RNA isoform diversity in aging Down syndrome brains

Down syndrome (DS) neurocognitive disabilities associated with trisomy 21 are known; however, gene changes within individual brain cells occurring with age are unknown. Here, we interrogated >170,000 cells from 29 aging DS and control brains using single-nucleus RNA sequencing. We observed increases in inhibitory-over-excitatory neurons, microglial activation in the youngest DS brains coinciding with overexpression of genes associated with microglial-mediated synaptic pruning, and overexpression of the chromosome 21 gene RUNX1 that may be a potential driving factor in microglial activation. Single-nucleus long-read sequencing revealed hundreds of thousands of unannotated RNA transcripts. These included diverse species for the Alzheimer’s disease gene—amyloid precursor protein—that contained intra-exonic junctions previously associated with somatic gene recombination, which was also identified in ∼8,000 other genes.

Down syndrome (DS), trisomy of human chromosome 21 (HSA21), is characterized by lifelong cognitive impairments and the development of the neuropathological hallmarks of Alzheimer’s disease (AD). The cellular and molecular modifications responsible for these effects are not understood. Here we performed single-nucleus RNA sequencing (snRNA-seq) employing both short- (Illumina) and long-read (Pacific Biosciences) sequencing technologies on a total of 29 DS and non-DS control prefrontal cortex samples. In DS, the ratio of inhibitory-to-excitatory neurons was significantly increased, which was not observed in previous reports examining sporadic AD. DS microglial transcriptomes displayed AD-related aging and activation signatures in advance of AD neuropathology, with increased microglial expression of C1q complement genes (associated with dendritic pruning) and the HSA21 transcription factor gene RUNX1. Long-read sequencing detected vast RNA isoform diversity within and among specific cell types, including numerous sequences that differed between DS and control brains. Notably, over 8,000 genes produced RNAs containing intra-exonic junctions, including amyloid precursor protein (APP) that had previously been associated with somatic gene recombination. These and related results illuminate large-scale cellular and transcriptomic alterations as features of the aging DS brain.

Common genetic signatures of Alzheimer's disease in Down Syndrome

Background: People with Down Syndrome (DS) are born with an extra copy of Chromosome (Chr) 21 and many of these individuals develop Alzheimer’s Disease (AD) when they age. This is due at least in part to the extra copy of the APP gene located on Chr 21. By 40 years, most people with DS have amyloid plaques which disrupt brain cell function and increase their risk for AD. About half of the people with DS develop AD and the associated dementia around 50 to 60 years of age, which is about the age at which the hereditary form of AD, early onset AD, manifests. In the absence of Chr 21 trisomy, duplication of APP alone is a cause of early onset Alzheimer’s disease, making it likely that having three copies of APP is important in the development of AD and in DS.

Methods: We investigate the relationship between AD and DS through integrative analysis of genesets derived from a MeSH query of AD and DS associated beta amyloid peptides, Chr 21, GWAS identified AD risk factor genes, and differentially expressed genes in individuals with DS.

Results:  Unique and shared aspects of each geneset were evaluated based on  functional enrichment analysis, transcription factor profile and network interactions. Genes that may be important to both disorders in the context of direct association with APP processing, Tau post translational modification  and network connectivity are ACSM1, APBA2, APLP1, BACE2, BCL2L, COL18A1, DYRK1A, IK, KLK6, METTL2B, MTOR, NFE2L2, NFKB1, PRSS1, QTRT1, RCAN1, RUNX1, SAP18 SOD1, SYNJ1, S100B.

Conclusions: Our findings confirm that oxidative stress, apoptosis, inflammation and immune system processes likely contribute to the pathogenesis of AD and DS which is consistent with other published reports.

Assessment of dementia in a clinical sample of persons with intellectual disability

BACKGROUND

Assessment of age-associated disorders has become increasingly important.

METHODS

In a clinical setting, people with intellectual disability with and without dementia were assessed retrospectively using the Neuropsychological Test Battery (NTB) and the Dementia Questionnaire for People with Learning Disabilities (DLD) at two different times to analyse neuropsychological changes and diagnostic validity. One group (n = 44) was assessed with both instruments, while the DLD was applied in 71 patients.

RESULTS

In the NTB (n = 44), only patients with dementia (n = 26) showed a decline in the NTB total score and three subscales. Receiver operating characteristic analysis revealed a diagnostic sensitivity of .67, a specificity of .81, and an area under the curve (AUC) of .767. In the DLD group (n = 71), only those with dementia displayed a decrease in the cognitive and social scale; diagnostic sensitivity and specificity values were low (.61/.63) and the AUC was .704.

CONCLUSIONS

Neuropsychological assessment was sensitive to detect cognitive changes over time. Sensitivity values of both instruments suggest a reassessment at a later time point.

Relationship between Apgar scores and long-term cognitive outcomes in individuals with Down syndrome

This study examined the contribution of the Apgar score at 1 and 5 min after birth to later cognitive functioning in 168 individuals with Down syndrome who were between 6 and 25 years of age at time of cognitive testing. Our results showed that a lower Apgar score at 1 min was related to a worse performance in later cognitive measures of receptive vocabulary, verbal comprehension and production, visual memory and working memory. Results also showed that a lower Apgar score at 5 min was only related to worse later outcomes of verbal comprehension and production and auditory working memory. Our findings suggest a need for future studies investigating how specific perinatal events reflected in the Apgar score are linked to later cognitive functioning in individuals with Down syndrome.

Translation and validation of the inflammatory bowel disease fatigue (IBD-F) patient self-assessment questionnaire

Introduction

Inflammatory bowel disease (IBD) is a group of chronic gastrointestinal diseases with frequent systemic complications that are incurable according to current knowledge. These diseases adversely affect various areas of life, lowering patients’ quality of life. One of the most frequently reported symptoms is fatigue.

Aim

Translation and validation of the IBD-F patient self-assessment scale with a Polish IBD population.

Material and methods

After consent from the author of the questionnaire had been obtained, the questionnaire was translated using the forward- and back-translation method. After arriving at the final Polish version of the questionnaire and ensuring that the questions and statements were comprehensible, the questionnaire was validated with a group of 129 IBD patients.

Results

High values of intraclass correlation coefficient (ICC) were achieved for overall results in both parts of the IBD-F questionnaire between test and retest (values exceeding 0.75). A high Cronbach’s α consistency coefficient was achieved for the entire IBD-F questionnaire, both in the test and in the retest (0.968 and 0.975, respectively). Broken down into parts, Cronbach’s α coefficient for Section I (presence and severity of fatigue) of the IBD-F questionnaire was 0.883, and for Section II (impact of fatigue on the person’s life) it was 0.966. All patients evaluating the Polish version of the IBD-F questionnaire deemed the content of the questions comprehensible.

Conclusions

The analysis of the results obtained, the Polish version of the IBD-F questionnaire was considered valid, reliable, and clinically useful.

Everyday Memory in People with Down Syndrome

Although memory functions in people with Down Syndrome (DS) have been studied extensively, how well people with DS remember things about everyday life is not well understood. In the current study, 31 adolescents/young adults with DS and 26 with intellectual disabilities (ID) of mixed etiology (not DS) participated. They completed an everyday memory questionnaire about personal facts and recent events (e.g., school name, breakfast). They also completed a standard laboratory task of verbal long-term memory (LTM) where they recalled a list of unrelated words over trials. Results did not indicate impaired everyday memory, but impaired verbal LTM, in people with DS relative to people with mixed ID. Furthermore, the laboratory verbal LTM task predicted everyday memory for both groups after taking into account mental age equivalent. Our research showed both an independence and a connection between everyday memory and the standard laboratory memory task and has important research and clinical implications.

Capturing cognitive and behavioral variability among individuals with Down syndrome: a latent profile analysis

BACKGROUND

There is a high degree of inter- and intra-individual variability observed within the phenotype of Down syndrome. The Down Syndrome Cognition Project was formed to capture this variability by developing a large nationwide database of cognitive, behavioral, health, and genetic information on individuals with Down syndrome, ages 6-25 years. The current study used the Down Syndrome Cognition Project database to characterize cognitive and behavioral variability among individuals with Down syndrome.

METHODS

Latent profile analysis was used to identify classes across a sample of 314 participants based on their cognition (IQ and executive functioning), adaptive and maladaptive behavior, and autism spectrum disorder symptomatology. A multivariate multinomial regression model simultaneously examined demographic correlates of class.

RESULTS

Results supported a 3-class model. Each class demonstrated a unique profile across the subdomains of cognition and behavior. The "normative" class was the largest (n = 153, 48%) and displayed a relatively consistent profile of cognition and adaptive behavior, with low rates of maladaptive behavior and autism symptomatology. The "cognitive" class (n = 109, 35%) displayed low cognitive scores and adaptive behavior and more autism symptomatology, but with low rates of maladaptive behavior. The "behavioral" class, the smallest group (n = 52, 17%), demonstrated higher rates of maladaptive behavior and autism symptomatology, but with cognition levels similar to the "normative" class; their adaptive behavior scores fell in between the other two classes. Household income and sex were the only demographic variables to differ among classes.

CONCLUSIONS

These findings highlight the importance of subtyping the cognitive and behavioral phenotype among individuals with Down syndrome to identify more homogeneous classes for future intervention and etiologic studies. Results also demonstrate the feasibility of using latent profile analysis to distinguish subtypes in this population. Limitations and future directions are discussed.

[Cognition in Down's Syndrome: Development across the Life Span and Neuropsychological Assessment in Adults]

Das Down-Syndrom ist die häufigste genetische Ursache einer Intelligenzminderung. Da Menschen mit einem Down-Syndrom ein erhöhtes Risiko aufweisen, an einer Alzheimer-Demenz zu erkranken, ist eine umfassende Untersuchung der kognitiven Funktionen indiziert, sowohl im jungen Erwachsenenalter (zur Erhebung des kognitiven Ausgangsniveaus) als auch im Verlauf zur Demenzdiagnostik. Das weite Spektrum an kognitiver Leistungsfähigkeit bei Menschen mit einem Down-Syndrom stellt eine diagnostische Herausforderung dar. Wir möchten daher einen Überblick geben (1) über die kognitive Entwicklung über die Lebensspanne, (2) über verschiedene mögliche Ursachen kognitiver Veränderungen bei erwachsenen Menschen mit einem Down-Syndrom und (3) über neuropsychologische Diagnostik und entsprechende Verfahren für den Erwachsenenbereich. Schließlich geben wir, auf der Grundlage unserer Erfahrungen, (4) allgemeine Empfehlungen zur Untersuchung und Befundinterpretation bei Menschen mit Intelligenzminderung.

Evaluation of Visuospatial Short-term and Working Memory from the First to Second Year of Life: A Novel Task

The prototypical tasks for assessing visuospatial memory in infancy are based on the search for a hidden object in two locations. Fewer studies include more locations, delayed responses nor changes in the object's position. Our aim was to assess the visuospatial short-term and working memory in 12, 15, 18 and 22-month-old children (N = 65). Assessment included our experimental task, a working memory task and a cognitive developmental scale. Short-term and working memory abilities increased markedly at 22 months compared to younger ages and the performance of the children in our experimental task is related to other tasks previously used.

Executive function in Down syndrome: A meta-analysis

BACKGROUND

Executive function (EF) refers to a set of cognitive processes involved in goal-oriented behavior-especially inhibition, attention shifting, and working memory. EF has been identified as a probable area of difficulty in Down syndrome (DS), but the exact nature of the difficulty has not been well-established.

AIMS

The meta-analysis sought to confirm or disconfirm EF as an area of difficulty in DS and elucidate an EF profile.

METHODS AND PROCEDURES

A random-effects meta-analysis was conducted on 57 studies that compared a group with DS to a typically developing (TD) mental age matched group on one or more executive function tasks. Heterogeneity was examined and moderators analyzed.

OUTCOMES AND RESULTS

The overall mean weighted effect size was large (d = -0.87), indicating poorer EF in groups with DS vs TD groups. Heterogeneity was significant, and moderator analysis revealed an EF profile with a very large effect for verbal WM/STM, a large effect for shifting, and moderate effects for inhibition and nonverbal WM/STM. Skewness analysis suggested that mean effect sizes might have been dampened, especially for WM/STM and shifting.

CONCLUSIONS AND IMPLICATIONS

Individuals with DS display a pronounced difficulty in EFs; implications for interventions and future research are discussed.

Common genetic signatures of Alzheimer's disease in Down Syndrome

Background: People with Down Syndrome (DS) are born with an extra copy of Chromosome (Chr) 21 and many of these individuals develop Alzheimer's Disease (AD) when they age. This is due at least in part to the extra copy of the APP gene located on Chr 21. By 40 years, most people with DS have amyloid plaques which disrupt brain cell function and increase their risk for AD. About half of the people with DS develop AD and the associated dementia around 50 to 60 years of age, which is about the age at which the hereditary form of AD, early onset AD, manifests. In the absence of Chr 21 trisomy, duplication of APP alone is a cause of early onset Alzheimer's disease, making it likely that having three copies of APP is important in the development of AD and in DS. In individuals with both DS and AD, early behavior and cognition-related symptoms may include a reduction in social behavior, decreased enthusiasm, diminished ability to pay attention, sadness, fearfulness or anxiety, irritability, uncooperativeness or aggression, seizures that begin in adulthood, and changes in coordination and walking. Methods: We investigate the relationship between AD and DS through integrative analysis of genesets derived from a MeSH query of AD and DS associated beta amyloid peptides, Chr 21, GWAS identified AD risk factor genes, and differentially expressed genes in DS individuals. Results: Unique and shared aspects of each geneset were evaluated based on functional enrichment analysis, transcription factor profile and network analyses. Genes that may be important to both disorders: ACSM1, APBA2, APLP1, BACE2, BCL2L, COL18A1, DYRK1A, IK, KLK6, METTL2B, MTOR, NFE2L2, NFKB1, PRSS1, QTRT1, RCAN1, RUNX1, SAP18 SOD1, SYNJ1, S100B. Conclusions: Our findings indicate that oxidative stress, apoptosis, and inflammation/immune system processes likely underlie the pathogenesis of AD and DS.

Intelligence trajectories in adolescents and adults with down syndrome: Cognitively stimulating leisure activities mitigate health and ADL problems

GOALS

This study examined: (a) crystallized/fluid intelligence trajectories of adolescents and adults with Down syndrome; and (b) the contribution of endogenous (health, activities of daily living-ADL) and exogenous (cognitively stimulating leisure activities) factors on adults' intelligence with age.

METHOD

Four cohorts (N = 80) with Down syndrome participated: adolescents (ages 16-21) and adults (ages 30-45, 46-60 and 61+). All completed Vocabulary and Similarities (crystallized) and Block Design and Raven (fluid) intelligence tests (WAIS-III^HEB , Wechsler, 2001).

RESULTS

The 30-45 cohort significantly outperformed the 16-21 cohort. Except for Vocabulary, which remained stable, onset of decline was at 40-50. Age-related declining health and ADL correlated with participants' lower fluid intelligence, but cognitive leisure activities mitigated this influence.

CONCLUSIONS

Intelligence development into adulthood supported the continuous trajectory and compensation age theory, rather than accelerated or stable trajectories. Not only endogenous factors but also exogenous factors determined intelligence levels in adults with Down syndrome, supporting cognitive activity theory.

The Acquisition of Survey Knowledge by Individuals With Down Syndrome

People with Down syndrome often exhibit deficiencies in wayfinding activities, particularly route learning (e.g., Courbois et al., 2013; Davis et al., 2014; Farran et al., 2015). Evidence concerning more sophisticated survey learning has been sparse. In the research reported here, two experiments are reported that evaluated survey learning of youth with DS and typically developing children (TD) matched on mental age. In Experiment 1, participants learned two overlapping routes consisting of three turns each through a virtual environment depicting 9 square city blocks. Following acquisition, they were tested on multiple measures of survey knowledge: finding a shortcut, identifying the direction of landmarks not currently visible from their location in the environment, and recognizing a bird's-eye representation of the overall environment. Under these conditions, which should provide relatively optimal opportunities for survey learning, the participants with DS performed comparably to TD participants matched on non-verbal ability on all of our measures of survey learning. Hence, we concluded that people with DS can acquire some survey knowledge when tasked with learning a small environment and given the opportunity to do so. In Experiment 2, the experimenter navigated participants through a large, relatively complex, virtual environment along a circuitous path, beginning and ending at a target landmark. Then, the participants were placed at a pre-specified location in the environment that they had viewed previously and instructed to navigate to the same target (a door) using the shortest possible path from their current location. They completed the task three times: once after being shown the environment one time, once after three exposures, and once after five exposures. Results indicated that the participants with DS exhibited significantly less skill at identifying the shortcut than did the TD participants, with differences emerging as the number of exposures increased. Participants with DS were also less able to recall landmarks at the end of the experiment. Overall, however, the performance of both groups was relatively poor in both experiments - with the performance of participants with DS being worse as conditions became less optimal. These results were discussed in terms of underlying mechanisms that may account for variations in survey learning as environmental complexity increases.

Validation of the NIH Toolbox Cognitive Battery in intellectual disability

OBJECTIVE

To advance the science of cognitive outcome measurement for individuals with intellectual disability (ID), we established administration guidelines and evaluated the psychometric properties of the NIH-Toolbox Cognitive Battery (NIHTB-CB) for use in clinical research.

METHODS

We assessed feasibility, test-retest reliability, and convergent validity of the NIHTB-CB (measuring executive function, processing speed, memory, and language) by assessing 242 individuals with fragile X syndrome (FXS), Down syndrome (DS), and other ID, ages 6 through 25 years, with retesting completed after 1 month. To facilitate accessibility and measurement accuracy, we developed accommodations and standard assessment guidelines, documented in an e-manual. Finally, we assessed the sensitivity of the battery to expected syndrome-specific cognitive phenotypes.

RESULTS

Above a mental age of 5.0 years, all tests had excellent feasibility. More varied feasibility across tests was seen between mental ages of 3 and 4 years. Reliability and convergent validity ranged from moderate to strong. Each test and the Crystallized and Fluid Composite scores correlated moderately to strongly with IQ, and the Crystallized Composite had modest correlations with adaptive behavior. The NIHTB-CB showed known-groups validity by detecting expected executive function deficits in FXS and a receptive language deficit in DS.

CONCLUSION

The NIHTB-CB is a reliable and valid test battery for children and young adults with ID with a mental age of ≈5 years and above. Adaptations for very low-functioning or younger children with ID are needed for some subtests to expand the developmental range of the battery. Studies examining sensitivity to developmental and treatment changes are now warranted.

Perceptual similarity effect in people with Down syndrome

Background The perceptual similarity between two objects, specifically similarity in the shape of the referents, is a crucial element for relating words in earlier stages of development. The role of this perceptual similarity has not been systematically explored in children with Down syndrome (DS). Method: The aim was to explore the role of perceptual similarity in relationships between words in children with DS. Two groups, children with typical development (TD) and children with DS, matched by gender and mental age, participated in a priming task with a preferential looking paradigm. The task presented validated perceptually-related word pairs (prime-target) and perceptually unrelated pairs. In the priming task both groups were asked to look at a target image (e.g. ball) that was perceptually related (e.g. cookie) or unrelated (e.g. skirt) to the prime. Results: Participants from both groups looked more at targets without perceptual similarity than at those with similarity to the prime, suggesting an inhibition effect. Conclusions: This finding suggests the role of visual information, particularly the shape of the referents, in the construction of the lexical system.

A comprehensive examination of the memory profile of youth with Down syndrome in comparison to typically developing peers

Down syndrome (DS) is associated with significant memory deficits beyond overall global cognitive impairment. Although a number of studies have examined memory abilities in adults and teens with DS, very few studies have examined memory abilities in children with DS. Additionally, research has yet to examine prospective memory (i.e., remembering to carry out an action in the future) in youth with DS. Consequently, the current study aimed to comprehensively examine the memory profile, including learning, immediate recall, delayed recall and prospective memory, of youth with DS (n = 22, age M = 11.43) in comparison to typically developing, mental-age (MA) matched children (n = 20, age M = 5.04) Consistent with past research, the results indicated that youth with DS performed significantly below MA-expectations on tasks of immediate verbal recall, learning across trials, and prospective memory, and there was a trend toward youth with DS performing below MA-expectations on delayed recall tasks. However, youth with DS did not differ significantly from MA-matched peers on immediate visual recall, rate of learning across trials, or proportion of items recalled on verbal and visual memory tasks following a delay (i.e., proportion relative to their own recall performance prior to the delay). These results highlight the relative strengths and challenges experienced by youth with DS on different learning and memory tasks. The implications of these findings for educators and caregivers are discussed.

Improving Cognitive Visual-Motor Abilities in Individuals with Down Syndrome

Down syndrome causes a reduction in cognitive abilities, with visual-motor skills being particularly affected. In this work, we have focused on this skill in order to stimulate better learning. The proposal relies on stimulating the cognitive visual-motor skills of individuals with Down Syndrome (DS) using exercises with a gestural interaction platform based on the KINECT sensor named TANGO:H, the goal being to improve them. To validate the proposal, an experimental single-case study method was designed using two groups: a control group and an experimental one, with similar cognitive ages. Didactic exercises were provided to the experimental group using visual cognitive stimulation. These exercises were created on the TANGO:H Designer, a platform that was designed for gestural interaction using the KINECT sensor. As a result, TANGO:H allows for visual-motor cognitive stimulation through the movement of hands, arms, feet and head. The "Illinois Test of Psycholinguistic Abilities (ITPA)" was applied to both groups as a pre-test and post-test in its four reference sections: visual comprehension, visual-motor sequential memory, visual association, and visual integration. Two checks were made, one using the longitudinal comparison of the pre-test/post-test of the experimental group, and another that relied on comparing the difference of the means of the pre-test/post-test. We also used an observational methodology for the working sessions from the experimental group. Although the statistical results do not show significant differences between the two groups, the results of the observations exhibited an improvement in visual-motor cognitive skills.

Projected Retained Ability Score (PRAS): A New Methodology for Quantifying Absolute Change in Norm-Based Psychological Test Scores Over Time

A limitation of norm-based ability test scores is that they can only be used to evaluate relative change (compared with change in the norm sample), as opposed to absolute (raw) change in performance from Time 1 to Time 2. To address this limitation, a novel method (Projected Retained Ability Score [PRAS]) was developed to characterize absolute change in norm-based ability test scores. The PRAS method was applied to Differential Ability Scales®–Second Edition (DAS-II) General Conceptual Ability (GCA) scores in three cases of children with the neurodegenerative condition mucopolysaccharidosis type II (MPS II) who were assessed at two visits, 16 to 23 months apart. Although all three cases showed declines in norm-based GCA scores, the PRAS method revealed differences in absolute change in performance. The PRAS method allows for differentiation of slower-than-average improvement or stabilization versus deterioration of cognitive ability when norm-based scores decline from Time 1 to Time 2.

Spaced training improves learning in Ts65Dn and Ube3a mouse models of intellectual disabilities

Benefits of distributed learning strategies have been extensively described in the human literature, but minimally investigated in intellectual disability syndromes. We tested the hypothesis that training trials spaced apart in time could improve learning in two distinct genetic mouse models of neurodevelopmental disorders characterized by intellectual impairments. As compared to training with massed trials, spaced training significantly improved learning in both the Ts65Dn trisomy mouse model of Down syndrome and the maternally inherited Ube3a mutant mouse model of Angelman syndrome. Spacing the training trials at 1 h intervals accelerated acquisition of three cognitive tasks by Ts65Dn mice: (1) object location memory, (2) novel object recognition, (3) water maze spatial learning. Further, (4) spaced training improved water maze spatial learning by Ube3a mice. In contrast, (5) cerebellar-mediated rotarod motor learning was not improved by spaced training. Corroborations in three assays, conducted in two model systems, replicated within and across two laboratories, confirm the strength of the findings. Our results indicate strong translational relevance of a behavioral intervention strategy for improving the standard of care in treating the learning difficulties that are characteristic and clinically intractable features of many neurodevelopmental disorders.

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.

Response Inhibition and Interference Suppression in Individuals With Down Syndrome Compared to Typically Developing Children

The present study aims to investigate inhibition in individuals with Down Syndrome compared to typically developing children with different inhibitory tasks tapping response inhibition and interference suppression. Previous studies that aimed to investigate inhibition in individuals with Down Syndrome reported contradictory results that are difficult to compare given the different types of inhibitory tasks used and the lack of reference to a theoretical model of inhibition that was tested in children (see Bunge et al., 2002; Gandolfi et al., 2014). Three groups took part in the study: 32 individuals with Down Syndrome (DS) with a mean age of 14 years and 4 months, 35 typically developing children 5 years of age (5TD), and 30 typically developing children 6 years of age (6TD). No difference emerged among the groups in fluid intelligence. Based on a confirmatory factor analysis, two different inhibition factors were identified (response inhibition and interference suppression), and two composite scores were calculated. An ANOVA was then executed with the composite inhibitory scores as dependent variables and group membership as the between-subject variable to explore the group differences in inhibition components. The 6TD group outperformed the 5TD group in both response inhibition and interference suppression component scores. No differences were found in both inhibition components between the DS group and 5TD. In contrast, the 6TD group outperformed the DS group in both response inhibition and in the interference suppression component's scores. Summarizing, our findings show that both response inhibition and interference suppression significantly increased during school transition and that individuals with DS showed a delay in both response inhibition and interference suppression components compared to typically developing 6-year-olds, but their performance was similar to typically developing 5-year-olds.