Mapping developmental trajectories of attention and working memory in fragile X syndrome: Developmental freeze or developmental change?

Similar Gap-Overlap Profiles in Children with Fragile X Syndrome and IQ-Matched Autism

PURPOSE

Fragile X syndrome (FXS) is a single-gene disorder characterized by moderate to severe cognitive impairment and a high association with autism spectrum disorder (ASD) and Attention-Deficit/Hyperactivity Disorder (ADHD). Atypical visual attention is a feature of FXS, ASD, and ADHD. Thus, studying early attentional patterns in young children with FXS can offer insight into early emerging neurocognitive processes underlying challenges and contribute to our understanding of common and unique features of ASD and ADHD in FXS.

METHODS

The present study examined visual attention indexed by the gap-overlap paradigm in children with FXS (n = 39) compared to children with ASD matched on intellectual ability and age (n = 40) and age-matched neurotypical controls (n = 34). The relationship between gap-overlap performance and intellectual ability, ASD, and ADHD across groups was characterized. Saccadic reaction times (RT) were collected across baseline, gap, and overlap conditions.

RESULTS

Results indicate no group differences in RT for any conditions. However, RT of the ASD and NT groups became slower throughout the experiment whereas RT of the FXS group did not change, suggesting difficulties in habituation for the FXS group. There was no relationship between RT and intellectual ability, ADHD, or ASD symptoms in the FXS and ASD groups. In the NT group, slower RT was related to elevated ADHD symptoms only.

CONCLUSION

Taken together, findings suggest that the social attention differences documented in FXS and ASD may be due to other cognitive factors, such as reward or motivation, rather than oculomotor control of visual attention.

ADHD and ASD symptoms in young males with fragile X syndrome: associations with early trajectories of inhibitory control

Inhibitory control (IC), the ability to suppress inappropriate responses, emerges late in the first year of life and improves across typical development, concurrent with brain maturation. The development of IC is critical to various social-emotional and behavioral functions, with IC difficulties being linked to numerous neurodevelopmental disorders, including attention-deficit/hyperactivity disorder (ADHD) and autism spectrum disorder (ASD). Fragile X syndrome (FXS) is a single-gene disorder characterized by IC difficulties, and elevated rates of ADHD and ASD, making it a useful model for understanding the early development and consequences of IC. In this longitudinal study, we characterized IC trajectories across multiple time points between 16 and 71 months of age in young males with FXS (n = 79) relative to neurotypical (NT) controls (n=49). To explore the association between behavioral outcomes and IC, we identified a subsample of 50 children with longitudinal IC data and an outcome assessment for ADHD and ASD symptoms at age 5 (FXS: n = 26, NT: n = 24). Results indicated that, compared to their NT peers, young males with FXS exhibit differences in IC as early as 24 months, with group differences increasing through age 5. Additionally, we determined that lower IC levels at 24 months were associated with later ADHD symptoms and a decreasing slope in IC over time was associated with later ASD symptoms in male children with FXS. These findings help refine early developmental phenotypes of FXS and highlight IC as a potential target for early detection and intervention of ASD and ADHD symptoms in male children with FXS.

Social Anxiety in Neurodevelopmental Disorders: The Case of Fragile X Syndrome

Despite significant advances in understanding and treating social anxiety in the general population, progress in this area lags behind for individuals with intellectual disability. Fragile X syndrome is the most common cause of inherited intellectual disability and is associated with an elevated prevalence rate of social anxiety. The phenotype of fragile X syndrome encompasses multiple clinically significant characteristics that are posed as risk markers for social anxiety in other populations. Here, evidence is reviewed that points to physiological hyperarousal, sensory sensitivity, emotion dysregulation, cognitive inflexibility, and intolerance of uncertainty as primary candidates for underlying mechanisms of heightened social anxiety in fragile X syndrome. A multilevel model is presented that provides a framework for future research to test associations.

Executive Function and Working Memory Deficits in Females with Fragile X Premutation

The Fragile X premutation is a genetic instability of the FMR1 gene caused by 55–199 recurrences of the CGG sequence, whereas there are only 7–54 repeats of the CGG sequence in the normal condition. While males with the premutation of Fragile X were found to have difficulties in executive functions and working memory, little data have been collected on females. This study is among the first to address executive functions and phonological memory in females with the Fragile X premutation. Twenty-three female carriers aged 20–55 years and twelve non carrier females matched in age and levels of education (in years) participated in this study. Executive functions and phonological memory were assessed using the self-report questionnaire The Behavior Rating Inventory of Executive Function (BRIEF) and behavioral measures (nonword repetitions, forward and backward digit span). Females who were carriers of the premutation of the FMR1 gene reported less efficient executive functions in the BRIEF questionnaire compared to the control group. In addition, a relationship was found between the number of repetitions on the CGG sequence of nucleotides, nonword repetitions, and forward digit span. The findings suggest that the premutation of Fragile X in females affects their performance of executive functions and may have impact on everyday functioning.

Re-visiting the 'mysterious myth of attention deficit': A systematic review of the recent evidence

Based on the inclusive and methodologically rigorous framework provided by Ed Zigler's developmental approach, we previously challenged what we called, 'the mysterious myth of attention deficit', the fallacy of attention as a universal deficit among persons with intellectual disability (ID). In this latest update, we conducted a systematic review of studies of essential components of attention among persons with ID published in the interim since the last iteration of the mysterious myth narrative was submitted for publication approximately a decade ago. We searched the databases PubMed and PsycINFO for English-language peer-reviewed studies published from 1 January 2011 through 5 February 2021. In keeping with the developmental approach, the two essential methodological criteria were that the groups of persons with ID were aetiologically homogeneous and that the comparisons with persons with average IQs (or with available norms) were based on an appropriate index of developmental level, or mental age. Stringent use of these criteria for inclusion served to control for bias in article selection. Articles were then categorised based on aetiological group studied and component of visual attention. Based on these criteria, 18 articles were selected for inclusion out of the 2837 that were identified. The included studies involved 547 participants: 201 participants with Down syndrome, 214 participants with Williams syndrome and 132 participants with fragile X syndrome. The findings from these articles call attention to the complexities and nuances in understanding attentional functioning across homogeneous aetiological groups and highlight that functioning must be considered in relation to aetiology; factors associated with the individual, such as developmental level, motivation, styles and biases; and factors associated with both the task, such as context, focus, social and emotional implications, and levels of environmental complexity.

Executive functions and their relationship with intellectual capacity and age in schoolchildren with intellectual disability

BACKGROUND

There is certain empirical evidence of, on the one hand, a positive correlation between executive functions (EFs) and intelligence in people with intellectual disability (ID) and, on the other hand, a slower rate of development of EFs in these people relative to people without ID. This evidence is not, however, unequivocal, and further studies are required.

METHODS

We analysed the relationship between development of EFs and both age and intellectual capacity, in a sample of 106 students with either ID or borderline intellectual functioning (BIF) at a special education centre [63 boys and 43 girls, 11-18 years old, mean total intelligence quotient (TIQ) of 59.6]. We applied nine instruments to evaluate both neuropsychological development (working memory, inhibitory control, cognitive flexibility, planning, processing speed and verbal fluency) and behavioural development [teachers' perceptions of the EFs of their students by Behavior Rating Inventory of Executive Function - Second Edition (BRIEF-2) School]. ID and BIF groups were statistically compared in terms of mean performance measures in EF tests. We looked at the correlation between EFs and age, and correlations between EFs and intelligence: TIQ, fluid intelligence [measured by the perceptual reasoning (PR) sub-index of Wechsler Intelligence Scale for Children-IV (WISC-IV)] and crystallised intelligence (measured by the verbal comprehension (VC) sub-index of WISC-IV). Regression models were built for variables with strong correlation.

RESULTS

In most of the tests used to evaluate EFs, the ID subgroup performed significantly worse than the subgroup with BIF. In general, teachers' thought that participants had 'medium-low' levels of EFs. TIQ, by WISC-IV scale, correlated significantly with scores in all tests for all EFs. The PR sub-index correlated significantly with 14 of the tests for EFs; 35% of the variation in PR can be explained by variation in performance in Picture Span (working memory) and Mazes (planning). The VC sub-index correlated weakly with seven of the EF tests. We found significant correlations in the ID group between age and scores in all tests of working memory and inhibitory control. Age - considering all participants - did not correlate with any of the variables of teachers' perception except for working memory, and this correlation was not strong.

CONCLUSIONS

The results of our study are consistent with descriptions of the typical population: (1) fluid intelligence is more related to EFs than crystallised intelligence is; and (2) working memory capacity is the EF most strongly related with general, fluid and crystallised forms of intelligence. The results suggest that as children and adolescents with ID/BIF get older, their capacities for working memory and inhibitory control increase; development of the other EFs studied was less evident. Teachers' perceptions of the EFs of children with ID or BIF were independent of intellectual capacity and age. More research is needed to delve further into the development of EFs in people with ID/BIF.

Responsive Parenting as a Target for Telehealth Language Interventions in Fragile X Syndrome: Implications for Scalability and Best Practices

This review highlights the ways in which telehealth procedures can be implemented to help bridge the research-to-practice gap in supporting developmental outcomes for youth with fragile X syndrome (FXS). We review how the literature to date has informed potential treatment targets in the areas of speech and language development with a focus on understanding and supporting the dyadic relationship between the child and their biological mother, who is also impacted biologically. Notably, parental responsivity is an area that is strongly related to child language outcomes, both early and into adolescence, and thus, it is an important treatment target for subsequent interventions. To date, several parent-implemented interventions have been done in FXS across a broad age range (2-17-year-olds) all showing support not only that parents are successful in learning responsive strategies but also that there are subsequent impacts to child language development. Moreover, these interventions were successfully implemented at a distance through telehealth procedures including video teleconferencing and shared recordings of parent-child interactions. This review also addresses potential moderators of treatment gains. Implications for scaling such interventions in the future as well as best practices for incorporating telehealth procedures into future research and intervention programs are also discussed.

Early behavioral and physiological markers of social anxiety in infants with fragile X syndrome

Background

Social anxiety is highly prevalent in neurotypical children and children with fragile X syndrome (FXS). FXS is a genetic syndrome that is characterized by intellectual disability and an increased risk for autism spectrum disorder. If social anxiety is left untreated, negative outcomes are highly prevalent later in life. However, early detection of social anxiety is challenging as symptoms are often subtle or absent very early in life. Given the prevalence and impairment associated with childhood social anxiety, efforts have accelerated to identify risk markers of anxiety. A cluster of early features of anxiety have been identified including elevated behavioral inhibition, attentional biases, and physiological dysregulation that index early emerging markers of social anxiety. Infants with FXS provide a unique opportunity to study the earlier predictors of social anxiety. The current study utilized a multi-method approach to investigate early markers of social anxiety in 12-month-old infants with FXS.

Method

Participants included 32 infants with FXS and 41 low-risk controls, all approximately 12 months old. Parent-reported social behavioral inhibition was recorded from the Infant Behavior Questionnaire (IBQ-R). Direct observations of behavioral inhibition and attention were measured during a stranger approach task with respiratory sinus arrhythmia collected simultaneously.

Results

Parent-reported social behavioral inhibition was not significantly different between groups. In contrast, direct observations suggested that infants with FXS displayed elevated behavioral inhibition, increased attention towards the stranger, and a blunted respiratory sinus arrhythmia response.

Conclusions

Findings suggest that infants with FXS show both behavioral and physiological markers of social anxiety at 12 months old using a biobehavioral approach with multiple sources of input. Results highlight the importance of a multi-method approach to understanding the complex early emergent characteristics of anxiety in infants with FXS.

Disentangling autism spectrum and attention-deficit/hyperactivity symptoms over development in fragile X syndrome

Even genetic disorders associated with monogenic aetiologies are characterized by complex and variable risk for poor outcomes, highlighting the need to follow trajectories longitudinally. Here, we investigated the longitudinal relationships between attention deficit hyperactivity disorder (ADHD) and autism spectrum disorder (ASD) symptoms in a population at high risk for both: boys with fragile X syndrome. 59 boys with fragile X syndrome aged 3-10 years old at entry participated in this study, and were followed up one and two years after their first visit. As expected, we found strong relationships over three timepoints for ADHD symptoms (as measured by the parent-rated Conners scale) and ASD symptoms (as measured by the Social Communication Questionnaire [SCQ]). In addition, using structural equation modeling (SEM) we found that ADHD symptoms at time 2 predicted ASD symptoms at time 3, suggestive of a causal relationship. Importantly, these relationships hold when including chronological age at entry to the study, as well as when including severity of impairment as measured by IQ, and their effects on both ASD and ADHD symptoms do not reach significance. This result highlights the need to study outcomes longitudinally and it informs the comorbidity of the two symptom domains in FXS as well as their potential directionality, both of which have been little researched. In addition, our findings may suggest a future need to study how ADHD symptoms and their treatment impact individuals with ASD.

Understanding attention, memory and social biases in fragile X syndrome: Going below the surface with a multi-method approach

Fragile X syndrome (FXS) is characterised by atypical social behaviours, such as gaze aversion. However, it remains unclear whether, or if so how, these behaviours affect cognitive processing and influence memory. We asked children with FXS (N = 16) and typically developing children (TD; N = 46) to explore naturalistic scenes containing social and non-social salient items unrelated to their task at hand (searching for a simple target object). We also assessed children's memory for target locations. We complemented behavioural responses with eye-tracking data for the subset of participants who managed to comply with calibration and the demands of the experimental testing session (6 children with FXS and 43 TD children). Children with FXS performed well at the experimental task, and showed similar accuracy and speed in locating targets in natural scenes to children of equivalent verbal abilities. They also learned target locations over blocks, but their memory of target locations was not as precise as that of comparison children. In addition, children with FXS initially directed few first looks to salient social items within the scenes, but these looks increased over blocks. Like TD children, children with FXS also dwelled gaze upon social items while recalling target locations from memory. Individual differences in everyday social characteristics also related to gaze and behavioural measures. In conclusion, experimental approaches can highlight cognitive underpinnings of atypical social behaviour in FXS, pinpointing both similarities and differences to TD individuals.

Relationship Between Task-Based and Parent Report-Based Measures of Attention and Executive Function in Children with Fetal Alcohol Spectrum Disorders (FASD)

A majority of children with fetal alcohol spectrum disorders (FASD) have demonstrated attention and executive function deficits as measured by both parent report measures and performance on tasks requiring sustained levels of attention. However, prior studies have consistently reported a lack of association between parental report-based and task-based performance measures. The current study investigated whether changes in performance over time within-task (i.e., first-half versus second-half) better correspond to parental reports of executive function and temperament in children with FASD. Greater differences in split-half performance during a continuous performance task were found to be associated with higher parent-reported levels of behavioral regulation and inhibitory control. These findings suggest that within-task performance differences may more accurately reflect individual differences in executive function and temperament as measured by parental report and help to further inform the way in which cognitive processes are measured in children with FASD.

Developmental studies in fragile X syndrome

Fragile X syndrome (FXS) is the most common single gene cause of autism and intellectual disabilities. Humans with FXS exhibit increased anxiety, sensory hypersensitivity, seizures, repetitive behaviors, cognitive inflexibility, and social behavioral impairments. The main purpose of this review is to summarize developmental studies of FXS in humans and in the mouse model, the Fmr1 knockout mouse. The literature presents considerable evidence that a number of early developmental deficits can be identified and that these early deficits chart a course of altered developmental experience leading to symptoms well characterized in adolescents and adults. Nevertheless, a number of critical issues remain unclear or untested regarding the development of symptomology and underlying mechanisms. First, what is the role of FMRP, the protein product of Fmr1 gene, during different developmental ages? Does the absence of FMRP during early development lead to irreversible changes, or could reintroduction of FMRP or therapeutics aimed at FMRP-interacting proteins/pathways hold promise when provided in adults? These questions have implications for clinical trial designs in terms of optimal treatment windows, but few studies have systematically addressed these issues in preclinical and clinical work. Published studies also point to complex trajectories of symptom development, leading to the conclusion that single developmental time point studies are unlikely to disambiguate effects of genetic mutation from effects of altered developmental experience and compensatory plasticity. We conclude by suggesting a number of experiments needed to address these major gaps in the field.

Executive Function in Fragile X Syndrome: A Systematic Review

Executive function (EF) supports goal-directed behavior and includes key aspects such as working memory, inhibitory control, cognitive flexibility, attention, processing speed, and planning. Fragile X syndrome (FXS) is the leading inherited monogenic cause of intellectual disability and is phenotypically characterized by EF deficits beyond what is expected given general cognitive impairments. Yet, a systematic review of behavioral studies using performance-based measures is needed to provide a summary of EF deficits across domains in males and females with FXS, discuss clinical and biological correlates of these EF deficits, identify critical limitations in available research, and offer suggestions for future studies in this area. Ultimately, this review aims to advance our understanding of the underlying pathophysiological mechanisms contributing to EF in FXS and to inform the development of outcome measures of EF and identification of new treatment targets in FXS.

The Influence of Hyperactivity, Impulsivity, and Attention Problems on Social Functioning in Adolescents and Young Adults With Fragile X Syndrome

OBJECTIVE

Individuals with fragile X syndrome (FXS) present primarily with cognitive and social deficits in addition to symptoms of ADHD. The relationship between symptoms of ADHD, cognitive functioning, and social skills has never been explicitly studied.

METHOD

Here, we analyzed both longitudinal ( n = 70; Time 1: ages 6-18; Time 2: ages 15-26) and cross-sectional ( n = 73; Time 2 only) data using hierarchical linear regression to assess how global intellectual functioning (IQ) and symptoms of ADHD influence social functioning in individuals with FXS.

RESULTS

We found that ADHD symptoms at Times 1 and 2 consistently predict social functioning in both males and females with FXS at Time 2.

CONCLUSION

Our results suggest that addressing ADHD symptoms in childhood may have positive, long-term effects on the social functioning of adolescents and young adults with FXS.

Developmental trajectories of executive functions in young males with fragile X syndrome

BACKGROUND

Executive functions (EF) have been identified as impaired in FXS, but few studies have examined their developmental trajectories.

AIMS

The primary aim of this longitudinal study was to examine the development of EF in young males with FXS compared to Mental Age (MA)-matched controls.

METHODS AND PROCEDURES

The sample comprised 56 boys with FXS (ages 7-13 years), and 48 MA-matched typical boys (ages 4-8 years). EF tasks included measures of inhibitory control, working memory, cognitive flexibility/set-shifting, problem solving/planning, and processing speed. Tasks were administered at three time points over five-years.

OUTCOMES AND RESULTS

The MA-Matched Typical boys significantly outperformed the FXS boys on all EF tasks, with the FXS Group showing a pattern of slow, but positive growth on most EF tasks. For working memory tasks, significant interactions were noted between MA and autism symptom severity, and MA and medication status. The probability of task completion increased with higher MA.

CONCLUSIONS AND IMPLICATIONS

These findings contribute to our understanding of the development of EF in this population. They also lay the foundation for use of EF tasks in treatment efforts, particularly with respect to documenting improvements and practice effects, and in understanding associations with targeted developmental outcomes.

A comparison of functional academic and daily living skills in males with fragile X syndrome with and without autism

BACKGROUND

Adaptive behaviors, such as functional academic and daily living skills, are critical for independence in adults with intellectual and developmental disabilities. However, little is known about these skills in fragile X syndrome (FXS), the most common form of inherited intellectual disability.

AIMS

The purposes of this study were to describe the functional academic and daily living skills of males diagnosed with FXS across different age groups and compare skill attainment by autism status and other common co-occurring conditions.

METHODS AND PROCEDURES

We used survey methods to assess parent-reported functional academic and daily living skills in 534 males with FXS. Functional academic skills included time and schedules, money, math, reading, and writing skills. Daily living skills included hygiene, cooking, laundry and housekeeping, transportation, and safety skills.

OUTCOMES AND RESULTS

Analyses examined functional academic and daily living skills in a cross-sectional sample of males between ages 5 and 67. Differences in skill attainment were found by child age, co-morbid autism status, total number of co-occurring conditions, and respondent education. Functional academic and daily living skills were predictive of community employment and independent living.

CONCLUSIONS AND IMPLICATIONS

These data provide important information on the mastery of both foundational and more complex adaptive skills in males with FXS. Both functional academic and daily living skills were predictive of measures of independence above and beyond other child and family characteristics. These findings point to the need to focus interventions to support the attainment of independence in males with FXS.

A Cross-Sectional and Longitudinal Study of Novel Metaphor and Metonymy Comprehension in Children, Adolescents, and Adults With Autism Spectrum Disorder

Previous studies have shown that comprehension of figurative language is impaired in individuals with autism spectrum disorder (ASD). However, most studies have focused on lexicalized expressions and have only examined performance at one particular point in time, without examining how performance changes over development. The current study examined the comprehension of novel metaphor and metonymy in individuals with ASDs from a large age range, using both a cross-sectional (Experiment 1) and longitudinal design (Experiment 2). Performance in the ASD group was lower compared to typically developing (TD) controls, across all ages. Importantly, the results from Experiments 1 and 2 showed that, although chronological age was not a good predictor for performance of either novel metaphor or metonymy in the cross-sectional design, performance improved when longitudinal data was considered. Correlations between vocabulary knowledge, visuo-spatial abilities and figurative language comprehension abilities were also explored.

The Emergence of Effortful Control in Young Boys With Fragile X Syndrome

Effortful control, or the ability to suppress a dominant response to perform a subdominant response, is an early-emerging temperament trait that is linked with positive social-emotional development. Fragile X syndrome (FXS) is a single-gene disorder characterized by hallmark regulatory impairments, suggesting diminished effortful control. This study compared the development of effortful control in preschool boys with FXS ( n = 97) and typical development ( n = 32). Unlike their typical peers, the boys with FXS did not exhibit growth in effortful control over time, which could not be accounted for by adaptive impairments, FMR1 molecular measures, or autism symptoms. These results contribute to our understanding of the childhood phenotype of FXS that may be linked to the poor social-emotional outcomes seen in this group.

Acamprosate rescues neuronal defects in the Drosophila model of Fragile X Syndrome

AIMS

Several off-label studies have shown that acamprosate can provide some clinical benefits in youth with Fragile X Syndrome (FXS), an autism spectrum disorder caused by loss of function of the highly conserved FMR1 gene. This study investigated the ability of acamprosate to rescue cellular, molecular and behavioral defects in the Drosophila model of FXS.

MAIN METHODS

A high (100μM) and low (10μM) dose of acamprosate was fed to Drosophila FXS (dfmr1 null) or genetic control (w¹¹¹⁸) larvae and then analyzed in multiple paradigms. A larval crawling assay was used to monitor aberrant FXS behavior, overgrowth of the neuromuscular junction (NMJ) was quantified to assess neuronal development, and quantitative RT-PCR was used to evaluate expression of deregulated cbp53E mRNA.

KEY FINDINGS

Acamprosate treatment partially or completely rescued all of the FXS phenotypes analyzed, according to dose. High doses rescued cellular overgrowth and dysregulated cbp53E mRNA expression, but aberrant crawling behavior was not affected. Low doses of acamprosate, however, did not affect synapse number at the NMJ, but could rescue NMJ overgrowth, locomotor defects, and cbp53E mRNA expression. This dual nature of acamprosate suggests multiple molecular mechanisms may be involved in acamprosate function depending on the dosage used.

SIGNIFICANCE

Acamprosate may be a useful therapy for FXS and potentially other autism spectrum disorders. However, understanding the molecular mechanisms involved with different doses of this drug will likely be necessary to obtain optimal results.

Cortisol profiles differentiated in adolescents and young adult males with fragile X syndrome versus autism spectrum disorder

BACKGROUND

Fragile X syndrome (FXS) and non-syndromic autism spectrum disorder (ASD) are distinct disorders with overlapping behavioral features. Both disorders are also highly associated with anxiety with abnormal physiological regulation implied mechanistically. Some reports suggest atypical hypothalamus-pituitary-adrenal (HPA) axis function, indexed via aberrant cortisol reactivity, in both FXS and non-syndromic ASD. However, no study has compared cortisol reactivity across these two disorders, or its relationship to ASD symptom severity.

METHODS

Cortisol reactivity (prior to and following a day of assessments) was measured in 54 adolescent/young adult males with FXS contrasted to 15 males with non-syndromic ASD who had low cognitive abilities.

RESULTS

Greater ASD symptom severity was related to increased cortisol reactivity and higher levels at the end of the day, but only in the non-syndromic ASD group. Elevated anxiety was associated with increased HPA activation in the group with FXS alone.

CONCLUSIONS

Taken together, findings suggest a unique neuroendocrine profile that distinguishes adolescent/young adult males with FXS from those with non-syndromic ASD. Severity of ASD symptoms appears to be related to cortisol reactivity in the non-syndromic ASD sample, but not in FXS; while anxiety symptoms are associated with HPA activation in the FXS sample, but not in ASD despite a high prevalence of ASD, anxiety and physiological dysregulation characteristic in both populations.

Visuo-spatial construction trajectories in Fragile X Syndrome (FXS) and Autism Spectrum Disorders (ASD): Evidence of cognitive heterogeneity within neurodevelopmental conditions

BACKGROUND/AIMS

There have been discrepancies reported in visuo-spatial construction ability in children with Autism Spectrum Disorders (ASD), fragile X Syndrome (FXS) and those with a comorbid diagnosis of FXS and ASD (AFXS). This study aimed to provide a better understanding of the visuo-spatial processing styles in these heterogeneous neurodevelopmental disorders.

METHODS AND PROCEDURE

Navon-type tasks were used to assess visuo-spatial construction ability across 5 groups of children: typically developing, FXS, AFXS, ASD children who scored low-moderate (HFA) and ASD children that scored severe (LFA) on the Childhood Autism Rating Scale (CARS). Analyses of their developmental trajectories compared the performance of these groups.

OUTCOMES AND RESULTS

Each group produced their own distinct trajectory. HFA achieved higher scores from an earlier age than the TD group, while the LFA group's performance was driven by a bias in local processing. The FXS performance was normalised by using mental age as a predictor while neither mental nor chronological age predicted the AFXS group performance.

CONCLUSIONS AND IMPLICATIONS

The study showed unique processing styles. These findings highlight the importance of taking comorbidity and the severity of symptoms within each condition into account in order to understand cognitive abilities and cognitive profiles.

Fragile X syndrome

Fragile X syndrome (FXS) is the leading inherited form of intellectual disability and autism spectrum disorder, and patients can present with severe behavioural alterations, including hyperactivity, impulsivity and anxiety, in addition to poor language development and seizures. FXS is a trinucleotide repeat disorder, in which >200 repeats of the CGG motif in FMR1 leads to silencing of the gene and the consequent loss of its product, fragile X mental retardation 1 protein (FMRP). FMRP has a central role in gene expression and regulates the translation of potentially hundreds of mRNAs, many of which are involved in the development and maintenance of neuronal synaptic connections. Indeed, disturbances in neuroplasticity is a key finding in FXS animal models, and an imbalance in inhibitory and excitatory neuronal circuits is believed to underlie many of the clinical manifestations of this disorder. Our knowledge of the proteins that are regulated by FMRP is rapidly growing, and this has led to the identification of multiple targets for therapeutic intervention, some of which have already moved into clinical trials or clinical practice.

Updated report on tools to measure outcomes of clinical trials in fragile X syndrome

OBJECTIVE

Fragile X syndrome (FXS) has been the neurodevelopmental disorder with the most active translation of preclinical breakthroughs into clinical trials. This process has led to a critical assessment of outcome measures, which resulted in a comprehensive review published in 2013. Nevertheless, the disappointing outcome of several recent phase III drug trials in FXS, and parallel efforts at evaluating behavioral endpoints for trials in autism spectrum disorder (ASD), has emphasized the need for re-assessing outcome measures and revising recommendations for FXS.

METHODS

After performing an extensive database search (PubMed, Food and Drug Administration (FDA)/National Institutes of Health (NIH)'s www.ClinicalTrials.gov, etc.) to determine progress since 2013, members of the Working Groups who published the 2013 Report evaluated the available outcome measures for FXS and related neurodevelopmental disorders using the COSMIN grading system of levels of evidence. The latter has also been applied to a British survey of endpoints for ASD. In addition, we also generated an informal classification of outcome measures for use in FXS intervention studies as instruments appropriate to detect shorter- or longer-term changes.

RESULTS

To date, a total of 22 double-blind controlled clinical trials in FXS have been identified through www.ClinicalTrials.gov and an extensive literature search. The vast majority of these FDA/NIH-registered clinical trials has been completed between 2008 and 2015 and has targeted the core excitatory/inhibitory imbalance present in FXS and other neurodevelopmental disorders. Limited data exist on reliability and validity for most tools used to measure cognitive, behavioral, and other problems in FXS in these trials and other studies. Overall, evidence for most tools supports a moderate tool quality grading. Data on sensitivity to treatment, currently under evaluation, could improve ratings for some cognitive and behavioral tools. Some progress has also been made at identifying promising biomarkers, mainly on blood-based and neurophysiological measures.

CONCLUSION

Despite the tangible progress in implementing clinical trials in FXS, the increasing data on measurement properties of endpoints, and the ongoing process of new tool development, the vast majority of outcome measures are at the moderate quality level with limited information on reliability, validity, and sensitivity to treatment. This situation is not unique to FXS, since reviews of endpoints for ASD have arrived at similar conclusions. These findings, in conjunction with the predominance of parent-based measures particularly in the behavioral domain, indicate that endpoint development in FXS needs to continue with an emphasis on more objective measures (observational, direct testing, biomarkers) that reflect meaningful improvements in quality of life. A major continuous challenge is the development of measurement tools concurrently with testing drug safety and efficacy in clinical trials.

Distance delivery of a parent-implemented language intervention for young boys with fragile X syndrome

BACKGROUND

In addition to significant cognitive delays, boys with fragile X syndrome display phenotypic characteristics that include delays in language, inattention, social anxiety, and escape-maintained challenging behaviors. Despite these challenges, families affected by fragile X syndrome often have limited access to center-based intervention programs.

METHODS

The present study utilized a multiple baseline design across participants to examine the preliminary effectiveness of a 12-week, parent-implemented spoken language intervention for three 5- to 7-year-old boys with fragile X syndrome. The goal of the intervention was to teach the biological mothers of each boy to use a set of verbally responsive language support strategies while participating in shared book reading activities with her child. All aspects of the intervention, including pre- and post-treatment measures, were delivered into the family's home via distance video teleconferencing.

RESULTS

Results from this study provide preliminary support for the efficacy of this parent-implemented language intervention approach by demonstrating generalized improvements in both targeted maternal strategy use and measures of child spoken language.

CONCLUSIONS

The present study expands upon prior language intervention research utilizing distance delivery of services for families affected by fragile X syndrome. Additionally, the study provides early support for the feasibility of collecting pre- and post-treatment assessments at a distance.

Developmental trajectories of hierarchical visuo-spatial processing in fragile X syndrome and ASD: Within- and cross-syndrome variability

BACKGROUND/AIMS

Despite the advances in understanding visuo-spatial processing in developmental disorders such as ASD and fragile X syndrome (FXS), less is known about the profile of those with a comorbid diagnosis, or the role of within-disorder disparities between individuals across the ASD spectrum.

METHODS AND PROCEDURES

Using a developmental trajectory approach, we tested 5 groups of children: Typically developing, FXS, FXS+ASD, ASD individuals who had low-moderate symptoms (HFA) and ASD individuals who had severe symptoms (LFA). Symptoms of ASD were assessed using the Childhood Autism Rating Scale: CARS and hierarchical visuo-spatial processing was assessed using the Navon task.

OUTCOMES AND RESULTS

Crucially, results differed between HFA and LFA participants. Furthermore, the pattern of results differed between those who had a diagnosis of FXS only and FXS+ASD. Poorer performance within the FXS groups and the group who are low functioning on the ASD spectrum indicated a delayed developmental rate compared to typical controls.

CONCLUSIONS AND IMPLICATIONS

This study showed that diagnosis and severity of symptoms are indicative of differences in visuo-spatial processing styles. It is important that heterogeneity within FXS and ASD populations are considered in subsequent studies and look beyond diagnostic group differences.

The emergence and stability of attention deficit hyperactivity disorder in boys with fragile X syndrome

BACKGROUND

Children with fragile X syndrome (FXS) are at high risk for developing a range of behavioural disorders, including attention deficit/hyperactivity disorder (ADHD) and autism spectrum disorders (ASD). However, very few studies have investigated the comorbid profile of FXS and ADHD and the possible dissociation from the FXS and ASD profile. The present study examined the relationship of childhood temperament characteristics of the Surgency facet (activity level, impulsivity, approach, shyness, and smiling and laughter) and the severity of ADHD and ASD features at two measurement time points in childhood, preschool (ages 3-4) and at school entry (ages 5-6).

METHODS

The study consisted of males with FXS measured at each time point (preschool and school entry), as well as comparison of typically developing (TD) boys at the preschool measurement time point. Parent reported measures of temperament and behavioural symptoms were collected at each time point. Multiple regression analyses were used to analyse obtained data.

RESULTS

Elevated activity level scores are associated with ADHD scores at preschool age and elevated shyness and decreased smiling and laughter are strongly associated with ADHD scores upon school entry. Impulsivity emerges as a strong indicator of elevated ADHD scores around school age, but even preschool impulsivity scores demonstrate some predictive value for higher ADHD scores later in school. Finally, no Surgency characteristic was significantly related to ASD scores at any age.

CONCLUSIONS

Impulsivity serves as an indicator of elevated ADHD symptoms across development periods in boys with FXS, while activity level is just indicative of higher ADHD scores at the preschool age. The Surgency facet of temperament at either age does not predict strong relationships of comorbid pathologies of ADHD and ASD in FXS. However, Surgency characteristics may serve as informative discriminative factors when studying behavioural outcomes in boys with FXS.

The cognitive developmental profile associated with fragile X syndrome: A longitudinal investigation of cognitive strengths and weaknesses through childhood and adolescence

Few studies have investigated developmental strengths and weaknesses within the cognitive profile of children and adolescents with fragile X syndrome (FXS), a single-gene cause of inherited intellectual impairment. With a prospective longitudinal design and using normalized raw scores (Z scores) to circumvent floor effects, we measured cognitive functioning of 184 children and adolescents with FXS (ages 6 to 16) using the Wechsler Scale of Intelligence for Children on one to three occasions for each participant. Participants with FXS received lower raw scores relative to the Wechsler Scale of Intelligence for Children normative sample across the developmental period. Verbal comprehension, perceptual organization, and processing speed Z scores were marked by a widening gap from the normative sample, while freedom from distractibility Z scores showed a narrowing gap. Key findings include a relative strength for verbal skills in comparison with visuospatial-constructive skills arising in adolescence and a discrepancy between working memory (weakness) and processing speed (strength) in childhood that diminishes in adolescence. Results suggest that the cognitive profile associated with FXS develops dynamically from childhood to adolescence. Findings are discussed within the context of aberrant brain morphology in childhood and maturation in adolescence. We argue that assessing disorder-specific cognitive developmental profiles will benefit future disorder-specific treatment research.

The attentive brain: insights from developmental cognitive neuroscience

Visual attention functions as a filter to select environmental information for learning and memory, making it the first step in the eventual cascade of thought and action systems. Here, we review studies of typical and atypical visual attention development and explain how they offer insights into the mechanisms of adult visual attention. We detail interactions between visual processing and visual attention, as well as the contribution of visual attention to memory. Finally, we discuss genetic mechanisms underlying attention disorders and how attention may be modified by training.

Use of emotional cues for lexical learning: a comparison of autism spectrum disorder and fragile X syndrome

The present study evaluated the ability of males with fragile X syndrome (FXS), nonsyndromic autism spectrum disorder (ASD), or typical development to learn new words by using as a cue to the intended referent an emotional reaction indicating a successful (excitement) or unsuccessful (disappointment) search for a novel object. Performance for all groups exceeded chance-levels in both search conditions. In the Successful Search condition, participants with nonsyndromic ASD performed similarly to participants with FXS after controlling for severity of ASD. In the Unsuccessful Search condition, participants with FXS performed significantly worse than participants with nonsyndromic ASD, after controlling for severity of ASD. Predictors of performance in both search conditions differed between the three groups. Theoretical and clinical implications are discussed.

Developmental changes in cognitive and behavioural functioning of adolescents with fragile-X syndrome

BACKGROUND

Individuals with fragile-X syndrome exhibit developmental delay, hyperexcitation and social anxiety; they also show lack of attention and hyperactivity. Few studies have investigated whether levels of functioning change with increasing age. Here, we explored developmental changes across adolescence in the cognitive and behavioural profile of individuals with fragile-X syndrome. To this scope, we assessed intellectual functioning, adaptive behaviour, autistic symptomatology, behavioural problems (e.g. hyperactivity/lack of attention) and strengths (prosocial behaviours).

METHOD

Thirty-six participants underwent standardised outcome measures (i.e. the Wechsler Intelligence Scales-Revised, the Childhood Autism Rating Scale, the Vineland Adaptive Behavior Scales, and the Strengths and Difficulty Questionnaire) in three time points (Time 1: 9-11; Time 2: 11-13, and Time 3: 13-15 years).

RESULTS

Verbal IQ improved across time, whereas Nonverbal IQ declined and Full Scale IQ was quite unchanged. Autism ratings decreased; communication and social aspects of adaptive behaviour also enhanced. Finally, elevated levels of hyperactivity/lack of attention at Time 1 significantly improved across the three time points, whereas emotional symptoms, behavioural difficulties, problems with peers and prosocial behaviours remained stable over time.

CONCLUSION

These findings revealed specific developmental changes in cognitive and behavioural functioning of individuals with fragile-X syndrome, likely related to a progressive maturation of brain systems devoted to attentional control.

From Learning to Memory: What Flies Can Tell Us about Intellectual Disability Treatment

Intellectual disability (ID), previously known as mental retardation, affects 3% of the population and remains without pharmacological treatment. ID is characterized by impaired general mental abilities associated with defects in adaptive function in which onset occurs before 18 years of age. Genetic factors are increasing and being recognized as the causes of severe ID due to increased use of genome-wide screening tools. Unfortunately drug discovery for treatment of ID has not followed the same pace as gene discovery, leaving clinicians, patients, and families without the ability to ameliorate symptoms. Despite this, several model organisms have proven valuable in developing and screening candidate drugs. One such model organism is the fruit fly Drosophila. First, we review the current understanding of memory in human and its model in Drosophila. Second, we describe key signaling pathways involved in ID and memory such as the cyclic adenosine 3',5'-monophosphate (cAMP)-cAMP response element binding protein (CREB) pathway, the regulation of protein synthesis, the role of receptors and anchoring proteins, the role of neuronal proliferation, and finally the role of neurotransmitters. Third, we characterize the types of memory defects found in patients with ID. Finally, we discuss how important insights gained from Drosophila learning and memory could be translated in clinical research to lead to better treatment development.

Uncovering the evidence for behavioral interventions with individuals with fragile X syndrome: a systematic review

Fragile X syndrome (FXS) is associated with a wide range of cognitive, emotional, and behavioral difficulties. Although there is considerable research on the behavioral phenotype of FXS, few empirical studies of behavioral interventions with this population have been identified. Through a hand search of 34 behavioral journals, we examined the evidence base for behavioral interventions with individuals with FXS and in light of the current state of knowledge regarding the FXS behavioral phenotype. Systematic review procedures were used to identify behavioral intervention studies that included at least one participant with FXS, extract and summarize the data on several relevant dimensions, and rate the methodological quality of the studies. Results revealed 31 intervention studies with a small number of participants with FXS. Overall, results suggest a behavioral approach to intervention with individuals with FXS shows promise. Future research focused on individuals with FXS will be necessary to continue to examine differences in response to intervention and interventions that specifically address phenotypic characteristics.

Annual research review: Rare genotypes and childhood psychopathology--uncovering diverse developmental mechanisms of ADHD risk

BACKGROUND

Through the increased availability and sophistication of genetic testing, it is now possible to identify causal diagnoses in a growing proportion of children with neurodevelopmental disorders. In addition to developmental delay and intellectual disability, many genetic disorders are associated with high risks of psychopathology, which curtail the wellbeing of affected individuals and their families. Beyond the identification of significant clinical needs, understanding the diverse pathways from rare genetic mutations to cognitive dysfunction and emotional-behavioural disturbance has theoretical and practical utility.

METHODS

We overview (based on a strategic search of the literature) the state-of-the-art on causal mechanisms leading to one of the most common childhood behavioural diagnoses - attention deficit hyperactivity disorder (ADHD) - in the context of specific genetic disorders. We focus on new insights emerging from the mapping of causal pathways from identified genetic differences to neuronal biology, brain abnormalities, cognitive processing differences and ultimately behavioural symptoms of ADHD.

FINDINGS

First, ADHD research in the context of rare genotypes highlights the complexity of multilevel mechanisms contributing to psychopathology risk. Second, comparisons between genetic disorders associated with similar psychopathology risks can elucidate convergent or distinct mechanisms at each level of analysis, which may inform therapeutic interventions and prognosis. Third, genetic disorders provide an unparalleled opportunity to observe dynamic developmental interactions between neurocognitive risk and behavioural symptoms. Fourth, variation in expression of psychopathology risk within each genetic disorder points to putative moderating and protective factors within the genome and the environment.

CONCLUSION

A common imperative emerging within psychopathology research is the need to investigate mechanistically how developmental trajectories converge or diverge between and within genotype-defined groups. Crucially, as genetic predispositions modify interaction dynamics from the outset, longitudinal research is required to understand the multi-level developmental processes that mediate symptom evolution.

Development of a New Attention Rating Scale for Children With Intellectual Disability: The Scale of Attention in Intellectual Disability (SAID)

Difficulties with attention, impulsivity, and hyperactivity are thought to be as common among children with intellectual disability (ID) as they are in children without ID. Despite this, there is a lack of scales to specifically assess ADHD symptomatology in children and adolescents with ID. This article describes the development and evaluation of a teacher-completed measure; the Scale of Attention in Intellectual Disability (SAID). A community survey of 176 teachers of children 5-13 years of age, with ID at all levels of impairment indicated that the T-SAID is a reliable and valid measure. Integrating this scale with neuropsychological and clinical research holds exciting promise for enhancing our understanding of the nature of attention difficulties within populations with ID.

Cognitive training as a resolution for early executive function difficulties in children with intellectual disabilities

Core executive functions (EF) such as attention, and working memory have been strongly associated with academic achievement, language development and behavioral stability. In the case of children who are vulnerable to cognitive and learning problems because of an underlying intellectual disability, EF difficulties will likely exacerbate an already compromised cognitive system. The current review examines cognitive training programs that aim to improve EF, specifically focusing on the potential of this type of intervention for children who have intellectual disabilities. We conclude that despite considerable discrepancies regarding reported intervention effects, these inconsistencies can be attributed to flaws in both program and study design. We discuss the steps needed to address these limitations and to facilitate the advancement of non-pharmaceutical interventions for children with intellectual disabilities.

Developmental trajectories of attentional control in preschool males with fragile X syndrome

Attention problems are among the most impairing features associated with fragile X syndrome (FXS). However, few studies have examined behavioral development of inhibitory control in very young children with FXS. We examined attentional control in 3-6 year boys with FXS using both an experimental inhibitory control paradigm and parent-report of attention problems. Study 1 examined attentional control in FXS compared to comparison groups matched on chronological and mental age. To determine the stability of impairments over time in FXS, Study 2 examined patterns of developmental change in an expanded longitudinal sample. Across studies, males with FXS demonstrated persistent impairments in inhibitory control and parent-reported attention problems. Inhibitory control was related to, but not solely driven by, lower mental age. Although parent-rated attention problems remained stable across ages, inhibitory control improved with time. Children with more severe attention problems often displayed initially poorer inhibitory control. However, these trajectories also improved more rapidly with age. Our findings indicate that despite persistent deficits in attentional control in young children with FXS, multi-method assessment can be used to capture developmental growth that should be further supported through early, targeted intervention.

Psychopathology and cognitive performance in individuals with membrane-associated guanylate kinase mutations: a functional network phenotyping study

BACKGROUND

Rare pathogenic variants in membrane-associated guanylate kinase (MAGUK) genes cause intellectual disability (ID) and have recently been associated with neuropsychiatric risk in the non-ID population. However, it is not known whether risk for psychiatric symptoms amongst individuals with ID due to MAGUK gene mutations is higher than expected for the degree of general intellectual impairment, nor whether specific cognitive differences are associated with disruption to this gene functional network.

METHODS

This study addresses these two questions via behavioural questionnaires and cognitive testing, applying quantitative methods previously validated in populations with ID. We compared males with X-linked ID caused by mutations in three MAGUK genes (PAK3, DLG3, OPHN1; n = 9) to males with ID caused by mutations in other X chromosome genes (n = 17). Non-parametric and parametric analyses were applied as appropriate to data.

RESULTS

Groups did not differ in age, global cognitive impairment, adaptive function or epilepsy prevalence. However, individuals with MAGUK gene mutations demonstrated significantly higher psychopathology risks, comprising elevated total problem behaviours, prominent hyperactivity and elevated scores on an autism screening checklist. Despite these overt difficulties, individuals in the MAGUK group performed more accurately than expected for age and intelligence quotient (IQ) on computerised tests of visual attention, convergent with mouse models of MAGUK loss-of-function.

CONCLUSIONS

Our findings support a role for MAGUK genes in influencing cognitive parameters relevant to psychiatric risk. In addition to establishing clear patterns of impairment for this group, our findings highlight the importance of careful phenotyping after genetic diagnosis, showing that gene functional network disruptions can be associated with specific psychopathological risks and cognitive differences within the context of ID.

Psychiatric assessment of severe presentations in autism spectrum disorders and intellectual disability

Children with autism spectrum and related disorders and intellectual disability are not protected from the experience of psychiatric illnesses. Many factors can contribute to exacerbation of existing behavioral symptoms or to the emergence of new psychiatric problems. The psychiatric assessment must thus take into account a range of possible etiologic or contributory factors. The approach outlined in this article highlights the value of assessing 4 broad domains, including diagnostic (genetic) factors, medical considerations, developmental influences, and environmental factors. Examples of how the consideration of each of these domains may inform the diagnostic formulation are highlighted.

Parsing eye-tracking data of variable quality to provide accurate fixation duration estimates in infants and adults

Researchers studying infants' spontaneous allocation of attention have traditionally relied on hand-coding infants' direction of gaze from videos; these techniques have low temporal and spatial resolution and are labor intensive. Eye-tracking technology potentially allows for much more precise measurement of how attention is allocated at the subsecond scale, but a number of technical and methodological issues have given rise to caution about the quality and reliability of high temporal resolution data obtained from infants. We present analyses suggesting that when standard dispersal-based fixation detection algorithms are used to parse eye-tracking data obtained from infants, the results appear to be heavily influenced by interindividual variations in data quality. We discuss the causes of these artifacts, including fragmentary fixations arising from flickery or unreliable contact with the eyetracker and variable degrees of imprecision in reported position of gaze. We also present new algorithms designed to cope with these problems by including a number of new post hoc verification checks to identify and eliminate fixations that may be artifactual. We assess the results of our algorithms by testing their reliability using a variety of methods and on several data sets. We contend that, with appropriate data analysis methods, fixation duration can be a reliable and stable measure in infants. We conclude by discussing ways in which studying fixation durations during unconstrained orienting may offer insights into the relationship between attention and learning in naturalistic settings.