A theoretical analysis of the role of hyperarousal in the learning and behavior of fragile X males

Adaptive group behavior of Fragile X mice in unfamiliar environments

Fragile X Syndrome (FXS) stands out as a prominent cause of inherited intellectual disability and a prevalent disorder closely linked to autism. FXS is characterized by substantial alterations in social behavior, encompassing social withdrawal, avoidance of eye contact, heightened social anxiety, increased arousal levels, language deficits, and challenges in regulating emotions. Conventional behavioral assessments primarily focus on short-term interactions within controlled settings. In this study, we conducted a comprehensive examination of the adaptive group behavior of Fmr1 KO male mice over a three-day period, without introducing experimental interventions or task-based evaluations. The data unveiled intricate behavioral anomalies, with the most significant changes manifesting during the initial adaptation to unfamiliar environments. Notably, certain behaviors exhibited a gradual return to typical patterns over time. This dynamic Fmr1 KO phenotype exhibited heightened activity, featuring increased exploration, amplified social interest, and an unconventional approach to social interactions characterized by a higher frequency of shorter engagements. These findings contribute to the growing understanding of social behavior in individuals with FXS and underscore the significance of comprehending their adaptive responses in various environmental contexts.

[Sensory regulation disorders in child psychiatry]

INTRODUCTION

The processing of sensory information determines the development and growth of a child's abilities. Dysfunction in the processing of sensory stimuli can affect a child's behavior and can disrupt development. Sensory Regulation Disorders are frequently associated with Autism Spectrum Disorder (ASD), with the DSM-5 even including it as a diagnostic criterion. However, they are also observed in other neurodevelopmental disorders. At present, the frequency of Sensory Regulation Disorders in children consulting child psychiatry has never been evaluated, although it seems to be a population at risk.

OBJECTIVES

To evaluate the frequency of sensory regulation disorders in children between 3 and 6 years old who first consult a child psychiatrist in Marseille. To determine whether certain reasons for consultation are correlated with the presence of sensory regulation disorders.

METHODS

A multicenter cross-sectional study was conducted for four months in Marseille. Sensory regulation disorders were assessed by the second version of Dunn's short sensory profile.

RESULTS

Fifty-eight patients were included. A significant difference was found between the frequency of SRT in our primary child psychiatry population and the general population. Subgroup analyses according to the reason for consultation showed that there would be more SRT in the Motor Instability/Inattention, Conduct Disorder and Socialization Disorder subgroups.

CONCLUSION

We observed a higher frequency of SRT in the child psychiatry consultation population. SRT could explain, or at least partly participate in, the children's symptomatology. The results are in favor of an early detection of SRT in the population of children consulting child psychiatry. The evaluation of the sensory profiles of these children allows a better understanding of the child's functioning and an adjustment of the intervention and support strategies proposed to the family.

Examining Phenotypic Differences in Gaze Avoidance Between Autism Spectrum Disorder and Fragile X Syndrome

We examined potential phenotypic differences in eye gaze avoidance exhibited by boys with autism spectrum disorder (ASD) and boys with fragile X syndrome (FXS). In Study 1, the Eye Contact Avoidance Scale (ECAS) was administered to caregivers of boys aged 7-18 years with FXS (n = 148), ASD (n = 168), and mixed developmental disabilities (MDD; n = 128). In Study 2, subsets of boys with FXS (n = 31) and boys with ASD (n = 25) received a brief behavioral treatment probe to improve eye contact. Results showed that boys with FXS obtained significantly higher scores on the ECAS compared to boys with ASD and MDD. Exposure to the brief behavioral treatment probe resulted in significant decreases in scores for boys with FXS, but not for boys with ASD.

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.

Cardiac Startle Response and Clinical Outcomes in Preschool Children With Fragile X Syndrome and Autism Spectrum Disorder

Objective: Poor physiological regulation in response to threat is linked to multiple negative developmental outcomes including anxiety, which is highly prevalent and impairing in young children with neurodevelopmental disabilities like fragile X syndrome (FXS) and autism spectrum disorder (ASD). The present study contrasted cardiac startle response in pre-school-aged children with FXS, with and without ASD, to children with non-syndromic ASD (nsASD) and neurotypical controls (NT). The relationship of cardiac startle to non-verbal mental age (NVMA), ASD severity, and parent-reported anxiety was also examined. Method: Four age-matched groups of pre-school children participated including those with FXS without ASD (FXS-Only, n = 21), FXS with ASD (FXS+ASD, n = 17), nsASD (n = 42), and NT children (n = 27). Participants viewed a silent movie during which a single 200 ms 98-decibel white noise burst occurred. Cardiac activity was analyzed for pre-stimulus respiratory sinus arrhythmia (RSA) and the inter-beat intervals (IBI) at the auditory stimulus and 10 s post-stimulus. The Spence Pre-school Anxiety Scale, Autism Diagnostic Observation Schedule-2nd Edition, and Mullen Scales of Early Learning were examined in relation to startle response. Results: The nsASD group demonstrated heightened cardiac activity at the auditory stimulus and 10 s post-stimulus compared to the NT controls. Neither of the FXS groups showed differences from any other group. Higher pre-stimulus RSA was associated with reduced cardiac response across groups, while the relationship between cognitive ability and ASD severity to cardiac response varied between groups. Parent-reported anxiety was not associated with cardiac response for any group. Conclusion: These findings demonstrate group distinctions in cardiac responses to auditory startle. Although FXS and ASD share behavioral characteristics, the nsASD group showed a heightened cardiac startle response compared to the NT group that was not present in the FXS groups with or without ASD. Non-verbal mental age was associated with greater stimulus or post-stimulus reactivity for all groups except the FXS+ASD group, which showed no association between startle response and any clinical outcomes. Increased understanding of the relationship between physiological regulation and clinical outcomes will assist in identifying the timing and targets for effective interventions for individuals with neurodevelopmental disabilities.

Trajectories of Heart Activity Across Infancy to Early Childhood Differentially Predict Autism and Anxiety Symptoms in Fragile X Syndrome

Background: Fragile X syndrome (FXS) is a monogenic disorder characterized by high rates of autism spectrum disorder (ASD) and anxiety. A longstanding "hyperarousal hypothesis" in FXS has argued that ANS dysfunction underpins many symptoms of FXS. However, the developmental onset and trajectory of ANS dysfunction, as well as the consequences of ANS dysfunction on later psychiatric symptoms, remain poorly understood in FXS. Insight into the emergence, trajectory, and consequences of ANS dysfunction across early development in FXS has critical implications for prevention, intervention, and optimal outcomes in both typical and atypical development. This longitudinal study investigated whether and when males with FXS evidence atypical ANS function from infancy through early childhood, and how trajectories of ANS function across infancy and early childhood predict ASD and anxiety symptom severity later in development. Methods: Participants included 73 males with FXS and 79 age-matched typically developing (TD) males. Baseline heart activity was recorded at multiple assessments between 3 and 83 months of age, resulting in 372 observations. General arousal and parasympathetic activity were indexed via interbeat interval (IBI) and respiratory sinus arrhythmia (RSA), respectively. ASD and anxiety symptoms were assessed at 36 months of age or later in a subgroup of participants (FXS n = 28; TD n = 25). Results: Males with FXS exhibited atypical patterns of developmental change in ANS function across infancy and early childhood. As a result, ANS dysfunction became progressively more discrepant across time, with the FXS group exhibiting significantly shorter IBI and lower RSA by 29 and 24 months of age, respectively. Shorter IBI at 24 months and a flatter IBI slope across development predicted elevated anxiety symptoms, but not ASD symptoms, later in childhood in both FXS and TD males. Reduced RSA at 24 months predicted elevated ASD symptoms, but not anxiety symptoms, in both groups. Developmental change in RSA across early development did not predict later anxiety or ASD symptoms. Conclusion: This is the first longitudinal study to examine the "hyperarousal hypothesis" in infants and young children with FXS. Findings suggest that hyperarousal (i.e., shorter IBI, lower RSA) is evident in males with FXS by 24-29 months of age. Interestingly, unique aspects of early ANS function differentially relate to later ASD and anxiety symptoms. General arousal, indexed by shorter IBI that becomes progressively more discrepant from TD controls, predicts later anxiety symptoms. In contrast, parasympathetic-related factors, indexed by lower levels of RSA, predict ASD symptoms. These findings support the "hyperarousal hypothesis" in FXS, in that ANS dysfunction evident early in development predicts later-emerging symptoms of ASD and anxiety. This study also have important implications for the development of targeted treatments and interventions that could potentially mitigate the long-term effects of hyperarousal in FXS.

A novel eye-tracking paradigm for indexing social avoidance-related behavior in fragile X syndrome

Fragile X syndrome (FXS) is characterized by hallmark features of gaze avoidance, reduced social approach, and social anxiety. The development of therapeutics to manage these symptoms has been hindered, in part, by the lack of sensitive outcome measures. This study investigated the utility of a novel eye-tracking paradigm for indexing social avoidance-related phenotypes. Adolescent/young adult-aged males with FXS (n = 24) and typical development (n = 23) participated in the study. Participants viewed faces displaying direct or averted gaze and the first fixation duration on the eyes was recorded as an index of initial stimulus registration. Fixation durations did not differ across the direction of gaze conditions in either group, although the control group showed longer initial fixations on the eyes relative to the FXS group. Shorter initial fixation on averted gaze in males with FXS was a robust predictor of the severity of their social avoidance behavior exhibited during a social greeting context, whereas parent-reported social avoidance symptoms were not related to performance in the semi-naturalistic context. This eye-tracking paradigm may represent a promising outcome measure for FXS clinical trials because it provides a quantitative index that closely maps onto core social avoidance phenotypes of FXS, can be completed in less than 20 min, and is suitable for use with individuals with low IQ.

Prevalence and Predictors of Anxiety Disorders in Adolescent and Adult Males with Autism Spectrum Disorder and Fragile X Syndrome

Anxiety disorders affect ~ 15-20% of youths without neurodevelopmental disorders, with persons having autism spectrum disorder (ASD) and fragile X syndrome (FXS) at elevated risk for anxiety disorders. Few studies have compared rates and predictors of anxiety disorders in adolescents with FXS or ASD. This study directly compares rates, predictors, and medication of anxiety disorders between age-matched, male adolescents with FXS (n = 31) or ASD (n = 20). Results indicate that 51.6% of FXS and 50.0% of ASD adolescents met criteria for an anxiety disorder. Cognitive scores and ASD severity did not predict anxiety. Of those with anxiety, ~ 40% of the FXS and 20% of the ASD participants were prescribed medications for anxiety.

A Multimethod Analysis of Pragmatic Skills in Children and Adolescents With Fragile X Syndrome, Autism Spectrum Disorder, and Down Syndrome

PURPOSE

Pragmatic language skills are often impaired above and beyond general language delays in individuals with neurodevelopmental disabilities. This study used a multimethod approach to language sample analysis to characterize syndrome- and sex-specific profiles across different neurodevelopmental disabilities and to examine the congruency of 2 analysis techniques.

METHOD

Pragmatic skills of young males and females with fragile X syndrome with autism spectrum disorder (FXS-ASD, n = 61) and without autism spectrum disorder (FXS-O, n = 40), Down syndrome (DS, n = 42), and typical development (TD, n = 37) and males with idiopathic autism spectrum disorder only (ASD-O, n = 29) were compared using variables obtained from a detailed hand-coding system contrasted with similar variables obtained automatically from the language analysis program Systematic Analysis of Language Transcripts (SALT).

RESULTS

Noncontingent language and perseveration were characteristic of the pragmatic profiles of boys and girls with FXS-ASD and boys with ASD-O. Boys with ASD-O also initiated turns less often and were more nonresponsive than other groups, and girls with FXS-ASD were more nonresponsive than their male counterparts. Hand-coding and SALT methods were largely convergent with some exceptions.

CONCLUSION

Results suggest both similarities and differences in the pragmatic profiles observed across different neurodevelopmental disabilities, including idiopathic and FXS-associated cases of ASD, as well as an important sex difference in FXS-ASD. These findings and congruency between the 2 language sample analysis techniques together have important implications for assessment and intervention efforts.

Improving social gaze behavior in fragile X syndrome using a behavioral skills training approach: a proof of concept study

Background

Individuals diagnosed with fragile X syndrome (FXS), the most common known inherited form of intellectual disability, commonly exhibit significant impairments in social gaze behavior during interactions with others. Although this behavior can restrict social development and limit educational opportunities, behavioral interventions designed to improve social gaze behavior have not been developed for this population. In this proof of concept (PoC) study, we examined whether administering a behavioral skills training package—discrete trial instruction (DTI) plus relaxation training—could increase social gaze duration in males with FXS.

Methods

As part of a larger clinical trial, 20 boys with FXS, aged 8 to 18 years, were randomized to receive DTI plus relaxation training administered at one of two prescribed doses over a 2-day period at our research center. Potential improvements in social gaze behavior were evaluated by direct observations conducted across trials during the training, and generalization effects were examined by administering a social challenge before and after the treatment. During the social challenge, social gaze behavior was recorded using an eye tracker and physiological arousal levels were simultaneously recorded by monitoring the child’s heart rate.

Results

Levels of social gaze behavior increased significantly across blocks of training trials for six (60%) boys who received the high-dose behavioral treatment and for three (30%) boys who received the low-dose behavioral treatment. Boys who received the high-dose treatment also showed greater improvements in social gaze behavior during the social challenge compared to boys who received the low-dose treatment. There was no effect of the treatment on physiological arousal levels recorded on the heart rate monitor at either dose.

Conclusions

These results suggest that appropriate social gaze behavior can be successfully taught to boys with FXS using a standardized behavioral skills training approach. Future studies will need to evaluate whether younger children with FXS might benefit from this treatment, and/or whether more naturalistic forms of behavioral skills training might be beneficial, before social gaze avoidance becomes established in the child’s repertoire.

Trial registration

ClinicalTrials.gov, NCT02616796. Registered 30 November 2015.

Sensory Difficulties in Children With an FMR1 Premutation

Abnormal sensory processing is one of the core characteristics of the fragile X phenotype. Studies of young children with fragile X syndrome (FXS) and the FMR1 premutation have shown sensory challenges as early as infancy and into early childhood. This study sought to examine differences in sensory difficulties in children with an FMR1 premutation compared with children with FXS and typically developing children. We conducted an online survey of 176 parents of affected children (FXS or FMR1 premutation). Most respondents were mothers who are Caucasian (86%), have a 4-year college or graduate degree (68%), and are married (92%). Children ranged in age from 5 to 18, with a mean age of 13.0 years (3.3 SD). Participants completed the BBC Sensory Scales, a 50-item Likert-type scale (1 = Almost Always, 4 = Almost Never) comprised of 8 subscales that assessed auditory processing, visual processing, tactile processing, and eating and feeding behaviors. Mean scores were calculated for the items and each of the subscales. Non-parametric tests examined differences in child and family-level variables. Across all BBCSS subscales, children with an FMR1 premutation displayed more sensory challenges than typically developing children. For six out of the eight subscales, children with the full mutation had the lowest scores indicating more sensory challenges, but this was closely followed by children with an FMR1 premutation. Fragile X status was associated with seven of the eight subscales; children with an FMR1 premutation did not differ from children with FXS on any of the subscales but had more digestive problems than children with no fragile X. Gender, autism status, and family income were also related to sensory sensitivities. In conclusion, these data provide further evidence that some children with an FMR1 premutation experience sensory difficulties that are similar to children with FXS but different than typically developing children.

A Screening Tool to Measure Eye Contact Avoidance in Boys with Fragile X Syndrome

We examined the reliability, validity and factor structure of the Eye Contact Avoidance Scale (ECAS), a new 15-item screening tool designed to measure eye contact avoidance in individuals with fragile X syndrome (FXS). Internal consistency of the scale was acceptable to excellent and convergent validity with the Social Responsiveness Scale, Second Edition (SRS-2) and the Anxiety, Depression, and Mood Scale (ADAMS) was good. Boys with a comorbid ASD diagnosis obtained significantly higher scores on the ECAS compared to boys without ASD, when controlling for communication ability. A confirmatory factor analysis indicated that a two-factor model (avoidance and aversion) provided an excellent fit to the data. The ECAS appears to be a promising reliable and valid tool that could be employed as an outcome measure in future pharmacological/behavioral treatment trials for FXS.

Signaling of noncomprehension in communication breakdowns in fragile X syndrome, Down syndrome, and autism spectrum disorder

The ability to indicate a failure to understand a message is a critical pragmatic (social) language skill for managing communication breakdowns and supporting successful communicative exchanges. The current study examined the ability to signal noncomprehension across different types of confusing message conditions in children and adolescents with fragile X syndrome (FXS), Down syndrome (DS), autism spectrum disorder (ASD), and typical development (TD). Controlling for nonverbal mental age and receptive vocabulary skills, youth with comorbid FXS and ASD and those with DS were less likely than TD controls to signal noncomprehension of confusing messages. Youth with FXS without ASD and those with idiopathic ASD did not differ from controls. No sex differences were detected in any group. Findings contribute to current knowledge of pragmatic profiles in different forms of genetically-based neurodevelopmental disorders associated with intellectual disability, and the role of sex in the expression of such profiles.

LEARNING OUTCOMES

Upon completion of this article, readers will have learned about: (1) the social-communicative profiles of youth with FXS, DS, and ASD, (2) the importance of signaling noncomprehension in response to a confusing message, and (3) the similarities and differences in noncomprehension signaling in youth with FXS (with and without ASD), DS, idiopathic ASD, and TD.

HPA axis function predicts development of working memory in boys with FXS

The present study examines verbal working memory over time in boys with fragile X syndrome (FXS) compared to nonverbal mental-age (NVMA) matched, typically developing (TD) boys. Concomitantly, the relationship between cortisol-a physiological marker for stress-and verbal working memory performance over time is examined to understand the role of physiological mechanisms in cognitive development in FXS. Participants were assessed between one and three times over a 2-year time frame using two verbal working memory tests that differ in complexity: memory for words and auditory working memory with salivary cortisol collected at the beginning and end of each assessment. Multilevel modeling results indicate specific deficits over time on the memory for words task in boys with FXS compared to TD controls that is exacerbated by elevated baseline cortisol. Similar increasing rates of growth over time were observed for boys with FXS and TD controls on the more complex auditory working memory task, but only boys with FXS displayed an association of increased baseline cortisol and lower performance. This study highlights the benefit of investigations of how dynamic biological and cognitive factors interact and influence cognitive development over time.

Quantifying naturalistic social gaze in fragile X syndrome using a novel eye tracking paradigm

A hallmark behavioral feature of fragile X syndrome (FXS) is the propensity for individuals with the syndrome to exhibit significant impairments in social gaze during interactions with others. However, previous studies employing eye tracking methodology to investigate this phenomenon have been limited to presenting static photographs or videos of social interactions rather than employing a real-life social partner. To improve upon previous studies, we used a customized eye tracking configuration to quantify the social gaze of 51 individuals with FXS and 19 controls, aged 14-28 years, while they engaged in a naturalistic face-to-face social interaction with a female experimenter. Importantly, our control group was matched to the FXS group on age, developmental functioning, and degree of autistic symptomatology. Results showed that participants with FXS spent significantly less time looking at the face and had shorter episodes (and longer inter-episodes) of social gaze than controls. Regression analyses indicated that communication ability predicted higher levels of social gaze in individuals with FXS, but not in controls. Conversely, degree of autistic symptoms predicted lower levels of social gaze in controls, but not in individuals with FXS. Taken together, these data indicate that naturalistic social gaze in FXS can be measured objectively using existing eye tracking technology during face-to-face social interactions. Given that impairments in social gaze were specific to FXS, this paradigm could be employed as an objective and ecologically valid outcome measure in ongoing Phase II/Phase III clinical trials of FXS-specific interventions.

Therapeutic Strategies in Fragile X Syndrome: From Bench to Bedside and Back

Fragile X syndrome (FXS), an inherited intellectual disability often associated with autism, is caused by the loss of expression of the fragile X mental retardation protein. Tremendous progress in basic, preclinical, and translational clinical research has elucidated a variety of molecular-, cellular-, and system-level defects in FXS. This has led to the development of several promising therapeutic strategies, some of which have been tested in larger-scale controlled clinical trials. Here, we will summarize recent advances in understanding molecular functions of fragile X mental retardation protein beyond the well-known role as an mRNA-binding protein, and will describe current developments and emerging limitations in the use of the FXS mouse model as a preclinical tool to identify therapeutic targets. We will review the results of recent clinical trials conducted in FXS that were based on some of the preclinical findings, and discuss how the observed outcomes and obstacles will inform future therapy development in FXS and other autism spectrum disorders.

A comparison of pragmatic language in boys with autism and fragile X syndrome

PURPOSE

Impaired pragmatic language (i.e., language use for social interaction) is a hallmark feature of both autism spectrum disorder (ASD) and fragile X syndrome (FXS), the most common known monogenic disorder associated with ASD. However, few cross-population comparisons of ASD and FXS have been conducted, and it is unclear whether pragmatic language profiles in these conditions overlap.

METHOD

The authors used seminaturalistic and standardized assessment methods to characterize pragmatic language abilities of 29 school-aged boys with idiopathic ASD, 38 with FXS and comorbid ASD, 16 with FXS without ASD, 20 with Down syndrome, and 20 with typical development.

RESULTS

Similar severity of pragmatic language deficits was observed in both of the groups with ASD (idiopathic and fragile X-associated). ASD comorbidity had a detrimental effect on the pragmatic language skills of the boys with FXS. Some different patterns emerged across the two pragmatic assessment tools, with more robust group differences observed in pragmatics assessed in a seminaturalistic conversational context.

CONCLUSION

These findings have implications for pragmatic language assessment and intervention, as well as for understanding the potential role of the fragile X gene, Fragile X Mental Retardation-1, in the pragmatic language phenotype of ASD.

Physiological arousal in autism and fragile X syndrome: group comparisons and links with pragmatic language

This study tested the hypothesis that pragmatic (i.e., social) language impairment is linked to arousal dysregulation in autism spectrum disorder (ASD) and fragile X syndrome (FXS). Forty boys with ASD, 39 with FXS, and 27 with typical development (TD), aged 4-15 years, participated. Boys with FXS were hyperaroused compared to boys with TD but did not differ from boys with ASD. Dampened vagal tone predicted pragmatic impairment in ASD, and associations emerged between cardiac activity and receptive/expressive vocabulary across groups. Findings support autonomic dysfunction as a mechanism underlying pragmatic impairment in ASD and suggest that biophysiological profiles are shared in ASD and FXS, which has implications for understanding the role of fragile X mental retardation-1 (FMR1, the FXS gene) in the pathophysiology of ASD.

Psychophysiological responses to emotional stimuli in children and adolescents with autism and fragile X syndrome

Individuals with autism demonstrate atypical and variable responses to social and emotional stimuli, perhaps reflecting heterogeneity of the disorder. The goal of this study was to determine whether unique profiles of psychophysiological responses to such stimuli could be identified in individuals diagnosed with autism spectrum disorder (ASD), with fragile X syndrome (FXS), and with comorbid autism and fragile X syndrome (ASD + FXS), and in typically developing (TYP) individuals. This study included 52 boys (ages 10-17): idiopathic ASD (n = 12), FXS (n = 12), comorbid ASD + FXS (n = 17), and TYP (n = 11). Physiological responses, including potentiated startle, electrodermal response, heart rate variability, and vagal tone, were collected concurrently while participants viewed emotionally evocative pictures of human faces or nonsocial images. Although some of these measures have been utilized separately for investigations on these diagnostic groups, they have not been considered together. Results using Kruskal-Wallis one-way analysis of variance by ranks indicate statistically significant differences in distributions of autonomic regulation responses between groups. The most notable differences were between the ASD group and both the FXS groups on measures of sympathetic activity, with FXS groups evincing increased activity. Also, both the ASD and ASD + FXS groups showed significantly decreased parasympathetic activity compared with FXS and TYP groups. In addition, the ASD + FXS group demonstrated a unique distribution of startle potentiation and arousal modulation. This study provides evidence that autonomic arousal and regulation profiles could be useful for distinguishing subgroups of autism and shed light on the variability underlying emotional responsivity.

Early identification of autism in fragile X syndrome: a review

Fragile X syndrome (FXS) is the leading genetic cause of autism, accounting for approximately 5% of autism cases with as many as 50% of individuals with FXS meeting DSM-IV-TR criteria for autistic disorder. Both FXS and idiopathic autism (IA) are attributed to genetic causes; however, FXS is an identified single gene disorder whereas autism is a complex disorder with multiple potential causes, some of which have been identified. Studies in IA have focused on the prospective longitudinal examination of infant siblings of children with autism as a target group due to their high risk of developing the disorder. We propose that this same model be applied to the study of infants with FXS. There is a lack of research focusing on the early development of autism within FXS and debate in the literature regarding how to best conceptualise this co-morbidity or whether it should be considered a co-morbid condition at all. Studying the emergence and stability of autism in infants with FXS has multiple benefits such as clarifying the underlying mechanisms of the development of autism in FXS and solidifying similarities and differences between co-morbid FXS with autism and IA. Infant research in both IA and FXS are discussed as well as conclusions and implications for practice and future research.

Hyper-reactivity in fragile X syndrome females: generalised or specific to socially-salient stimuli? A skin conductance study

Fragile X syndrome (FXS) is characterised by hyper-reactivity, autistic tendencies and social anxiety. It has been hypothesised that the FXS social phenotype is secondary to a generalised hyper-reactivity that leads to social avoidance. No study, however, has investigated whether hyperarousal in FXS is generalised or more specific to socially salient information. We recorded skin conductance responses (SCRs) while females with FXS, as well as chronological age-(CA-) and mental age-(MA-) matched controls, viewed two sets of visual images: direct-gaze emotional faces and affectively arousing scenes. Explicit emotion recognition and subjective ratings of emotions aroused by images were also recorded. Overall, females with FXS displayed hyper-reactivity only when viewing the more socially salient stimuli (emotional faces), compared to CA-matched controls, but not MA-matched controls. Moreover, females with FXS also displayed atypical emotion recognition abilities and subjective ratings of their own emotional states. These findings suggest that any hyper-reactivity observed in FXS may be more specific to socially salient stimuli, rather than generalised.

Cardiovascular and behavioral response to auditory stimuli in boys with fragile X syndrome

OBJECTIVE

The aim of this study was to determine whether young boys with fragile X syndrome (FXS) exhibit abnormal physiological or behavioral responses to a moderately intense auditory stimulus, as heightened sensory reactivity is believed to contribute to problem behaviors in this population.

METHODS

We examined the physiological basis, via heart activity, of auditory startle in young boys with FXS (n = 22) compared with typically developing controls (n = 27). Associations with mental age, behavioral reactivity, and chronological age were examined.

RESULTS

Results suggest that older boys with FXS display increased cardiac reactivity to auditory input than younger boys with FXS that distinguishes them from typically developing controls. Higher mental age was associated with decreased latency to react.

CONCLUSIONS

Results contribute to increased understanding of the pathology in sensory processing in boys with FXS, which can inform refinement of the phenotype in young children with FXS and aid in the development of efficacious psychopharmacological and/or behavioral interventions.

Visual attention and autistic behavior in infants with fragile X syndrome

Aberrant attention is a core feature of fragile X syndrome (FXS), however, little is known regarding the developmental trajectory and underlying physiological processes of attention deficits in FXS. Atypical visual attention is an early emerging and robust indictor of autism in idiopathic (non-FXS) autism. Using a biobehavioral approach with gaze direction and heart activity, we examined visual attention in infants with FXS at 9, 12, and 18 months of age with a cross-sectional comparison to 12-month-old typically developing infants. Analyses revealed lower HR variability, shallower HR decelerations, and prolonged look durations in 12-month old infants with FXS compared to typical controls. Look duration and increased latency to disengage attention were correlated with severity of autistic behavior but not mental age.

Behavioural phenotypes and special educational needs: is aetiology important in the classroom?

BACKGROUND

A number of genetic conditions with associated intellectual disability and/or special educational needs have increasingly well-defined behavioural phenotypes. Thus, the concept of 'behavioural phenotype' and aetiology of intellectual disability may be important with regard to school-based interventions.

METHOD

The evidence for distinctive cognitive and behavioural aspects of five of the most common genetic syndromes (Down syndrome, fragile X syndrome, Williams syndrome, Prader-Willi syndrome and velo-cardio-facial syndrome) associated with special educational needs is reviewed with respect to key studies and findings. The possible utility of aetiology-related interventions in education is discussed with reference to arguments for and against such approaches with respect to published guidelines and published research.

RESULTS

Behavioural phenotypes are probabilistic and many children with a specific genetic syndrome will share commonalities with other children with other genetic syndromes and within syndrome variability is not uncommon. There is evidence that teachers and parents have limited knowledge of aspects of the proposed cognitive and behaviour profiles associated with the reviewed syndromes. While there are published guidelines in the area of learning and behaviour for each of the five reviewed syndromes there is a limited amount of evidence of the efficacy of such approaches in school settings.

CONCLUSION

It is likely that knowing the aetiology of a child's special educational needs will be helpful for staff who work in school settings in relation to cognitive and behavioural implications. However, how such knowledge might inform teaching practice or behavioural interventions has not been studied. A model is proposed that might help inform educators about the possible role of aetiology in the classroom.

Implicit procedural learning in fragile X and Down syndrome

BACKGROUND

Procedural learning refers to rule-based motor skill learning and storage. It involves the cerebellum, striatum and motor areas of the frontal lobe network. Fragile X syndrome, which has been linked with anatomical abnormalities within the striatum, may result in implicit procedural learning deficit.

METHODS

To address this issue, a serial reaction time (RT) task including six blocks of trials was performed by 14 individuals with fragile X syndrome, 12 individuals with Down syndrome and 12 mental age-matched control subjects. The first (B1) and fifth (B5) blocks were random whereas the others (B2, B3, B4 and B6) consisted of a repeated 10-step sequence. Results were analysed by Kruskal-Wallis one-way analysis of variance and Wilcoxon signed-rank test.

RESULTS

For patients with fragile X syndrome, the RT was highly suggestive of preserved implicit learning as a significant difference was observed between blocks B5 and B6 (P = 0.009). However, the difference of RT between B4 and B5 did not reach significance, possibly due to a subgroup of individuals who did not learn. In contrast, in the Down syndrome group, RT decreased significantly between B4 and B5 (W = 2; P = 0.003) but not between the last ordered block (B6) and the last random block (B5), suggesting a weakness in procedural learning which was sensitive to the interfering random block.

CONCLUSION

implicit learning is variable in genetic syndromes and therefore relatively independent of general intellectual capacities. The results are discussed together with previous reports.

The expression and assessment of emotions and internal states in individuals with severe or profound intellectual disabilities

The expression of emotions and internal states by individuals with severe or profound intellectual disabilities is a comparatively under-researched area. Comprehensive or standardized methods of assessing or understanding the emotions and internal states within this population, whose ability to communicate is significantly compromised, do not exist. The literature base will be discussed and compared to that applicable to the general population. Methods of assessing broader internal states, notably depression, anxiety, and pain within severe or profound intellectual disabilities are also addressed. Finally, this review will examine methods of assessing internal states within genetic syndromes, including hunger, social anxiety, and happiness within Prader-Willi, Fragile-X and Angelman syndrome. This will allow for identification of robust methodologies used in assessing the expression of these internal states, some of which may be useful when considering how to assess emotions within individuals with intellectual disabilities.

Fragile X: leading the way for targeted treatments in autism

Two different mutations in the FMR1 gene may lead to autism. The full mutation, with >200 CGG repeats in the 5' end of FMR1, leads to hypermethylation and transcriptional silencing of FMR1, resulting in absence or deficiency of the protein product, FMRP. Deficiency of FMRP in the brain causes fragile X syndrome (FXS). Autism occurs in approximately 30% of those with FXS, and pervasive developmental disorders-not otherwise specified occur in an additional 30%. FMRP is an RNA binding protein that modulates receptor-mediated dendritic translation; deficiency leads to dysregulation of many proteins important for synaptic plasticity. Group I metabotropic glutamate receptor (mGluR1/5) activated translation is upregulated in FXS, and new targeted treatments that act on this system include mGluR5 antagonists and GABA agonists, which may reverse the cognitive and behavioral deficits in FXS. Matrix metalloproteinase 9 (MMP-9) is one of the proteins elevated in FXS, and minocycline reduces excess MMP-9 activity in the Fmr1 knockout mouse model of FXS. Both minocycline and mGluR5 antagonists are currently being evaluated in patients with FXS through controlled treatment trials. The premutation (55-200 CGG repeats) may also contribute to the mechanism of autism in approximately 10% of males and 2-3% of females. Premutations with <150 repeats exert cellular effects through a different molecular mechanism, one that involves elevated levels of FMR1 mRNA, CGG-mediated toxicity to neurons, early cell death, and fragile X-associated tremor/ataxia syndrome. In those with large premutations (150-200), lowered levels of FMRP also occur.

Ethical, legal, and social concerns about expanded newborn screening: fragile X syndrome as a prototype for emerging issues

Technology will make it possible to screen for fragile X syndrome and other conditions that do not meet current guidelines for routine newborn screening. This possibility evokes at least 8 broad ethical, legal, and social concerns: (1) early identification of fragile X syndrome, an "untreatable" condition, could lead to heightened anxiety about parenting, oversensitivity to development, alterations in parenting, or disrupted bonding; (2) because fragile X syndrome screening should be voluntary, informed consent could overwhelm parents with information, significantly burden hospitals, and reduce participation in the core screening program; (3) screening will identify some children who are or appear to be phenotypically normal; (4) screening might identify children with other conditions not originally targeted for screening; (5) screening could overwhelm an already limited capacity for genetic counseling and comprehensive care; (6) screening for fragile X syndrome, especially if carrier status is disclosed, increases the likelihood of negative self-concept, societal stigmatization, and insurance or employment discrimination; (7) screening will suggest risk in extended family members, raising ethical and legal issues (because they never consented to screening) and creating a communication burden for parents or expanding the scope of physician responsibility; and (8) screening for fragile X syndrome could heighten discrepancies in how men and women experience genetic risk or decide about testing. To address these concerns we recommend a national newborn screening research network; the development of models for informed decision-making; materials and approaches for helping families understand genetic information and communicating it to others; a national forum to address carrier testing and the disclosure of secondary or incidental findings; and public engagement of scientists, policy makers, ethicists, practitioners, and other citizens to discuss the desired aims of newborn screening and the characteristics of a system needed to achieve those aims.

Sex differences in tactile defensiveness in children with ADHD and their siblings

Tactile defensiveness (TD) is a disturbance in sensory processing and is observed in some children with attention-deficit-hyperactivity disorder (ADHD). TD has been examined in male children with ADHD and in children with ADHD without differentiating by sex. As males and females with ADHD may differ in the clinical expression of the disorder and associated deficits, the aim of this study was to examine sex differences in TD in males and females with ADHD. Non-affected siblings were also examined to investigate familiality of TD. The Touch Inventory for Elementary-School-Aged Children was administered to 47 children with ADHD (35 males, 12 females; mean age 9y 8mo [SD 1y 11mo]), 36 non-affected siblings (21 males, 15 females; mean age 8y 10mo [SD 2y 4mo]), and 35 control children (16 males, 19 females; mean age 9y 5mo [SD 6mo]). Results indicated that females with ADHD displayed higher levels of TD than males with ADHD (who did not differ from control males). This suggests that TD is sex specific and may contribute to the identification of ADHD in females, thus improving diagnostic and therapeutic strength in this under-referred group. Non-affected siblings were unimpaired, regardless of sex, which suggests that TD is specific to the disorder and not part of a familial risk for ADHD.

Developmental trajectories and correlates of sensory processing in young boys with fragile X syndrome

BACKGROUND AND PURPOSE

No longitudinal study on sensory processing in children with fragile X syndrome (FXS) exists. This study examined developmental trajectories and correlates of sensory processing from infancy through preschool years in 13 boys with FXS.

METHOD

Participants were assessed using observational and parent-report measures 2-6 times between 9 and 54 months of age.

RESULTS

Over time, an increasing proportion of boys displayed sensory processing that differed significantly from test norms. Observational measures were more sensitive than parent-reports early in infancy. Age and developmental quotient significantly predicted levels of hyporesponsiveness; there was a trend for hyperresponsiveness to increase with age. Baseline physiological and biological measures were not predictive.

CONCLUSIONS

Sensory processing problems are observable early and grow increasingly problematic from infancy through the preschool ages. Early identification and intervention may attenuate long-term difficulties for children with FXS.

Autism spectrum phenotype in males and females with fragile X full mutation and premutation

The behavioural phenotype of autism was assessed in individuals with full mutation and premutation fragile X syndrome (FXS) using the Autism Diagnostic Observation Scale-Generic (ADOS-G) and the Autism Diagnostic Interview (ADI-R). The participants, aged 5-80 years, comprised 33 males and 31 females with full mutation, 7 males and 43 females with premutation, and 38 non-fragile X relatives (29 males, 9 females). In the full mutation group, a total of 67% males and 23% females met either the Autism Disorder (AD) or the Autism Spectrum Disorder (ASD) criteria on at least one of the diagnostic tests. In the premutation group, 14% males and 5% females met the ADOS-G criteria for ASD. The presence of autism manifestations in males and females with full mutation and premutation provide support for a spectrum view.

Discourse skills of boys with fragile X syndrome in comparison to boys with Down syndrome

PURPOSE

This study compared the conversational discourse skills of boys who have fragile X syndrome with and without autism spectrum disorder (ASD) with those of boys with Down syndrome and boys who are typically developing.

METHOD

Participants were boys who have fragile X syndrome with (n = 26) and without (n = 28) ASD, boys with Down syndrome (n = 29), and boys who are typically developing (n = 22). Turns during an examiner-child interaction consisting of structured and semistructured activities were coded for the boys' ability to maintain a topic of conversation and the frequency of perseveration.

RESULTS

The results revealed that boys who had both fragile X and ASD produced significantly more noncontingent discourse than did boys who had only fragile X, boys with Down syndrome, or typically developing boys. This finding was observed regardless of whether the topic was maintained or changed and whether the turn type was a response or initiation. Regardless of autism status, boys with fragile X used more perseveration than did boys in the other groups.

CONCLUSION

These findings suggest that some aspects of the conversational discourse difficulties attributed to fragile X syndrome may be a function of the high rate of comorbidity between fragile X and autism, whereas some difficulties may be characteristic of fragile X syndrome.

Language development and fragile X syndrome: profiles, syndrome-specificity, and within-syndrome differences

Fragile X syndrome (FXS) is the leading inherited cause of mental retardation. In this article, we review what is known about the language and related problems of individuals with FXS. In doing so, we focus on the syndrome-specific features of the language phenotype and on the organismic (i.e., genetic and individual neurocognitive and behavioral) and environmental factors associated with within-syndrome variation in the phenotype. We also briefly review those aspects of the behavioral phenotype of FXS that are relevant for understanding syndrome-specific features of, and within-syndrome variability in, language. The review includes summaries of research on the prelinguistic foundations for language development and on each of the major components of language (i.e., vocabulary, morphosyntax, and pragmatics). Throughout the review, we point out implications of existing research for intervention as well as directions for future research.

Language use in females with fragile X or Turner syndrome during brief initial social interactions

Fragile X and Turner syndromes are associated with risk of atypical social function. We examined language use, including normal and atypical speech, during initial social interactions among participants engaged in a brief social role play with an unfamiliar adult. There were 27 participants with Turner syndrome, 20 with fragile X syndrome and 28 in an age-matched comparison group. Females with fragile X did not exhibit more abnormal language, but exhibited less of what is typical during initial interactions. Overall rates of dysfluencies did not differ, although females with fragile X made more phrase repetitions. Females with Turner syndrome had no language use abnormalities. Our findings suggest that language use may influence social function in females with fragile X syndrome and that such language characteristics may be observed in the context of brief encounters with an unfamiliar adult.

A population-based twin study of parentally reported tactile and auditory defensiveness in young children

Some adults and children exhibit defensive behaviors to tactile or auditory stimulation. These symptoms occur not only in subsets of children with ADHD, autism, and Fragile X syndrome, but also in the apparent absence of accompanying disorders. Relatively little research explores the correlates and antecedents of sensory defensiveness. Using a population-based sample of 1,394 toddler-aged twins, mothers reported on tactile and auditory defensiveness, temperament, and behavior problems. The incidence of defensive symptoms was widely distributed, with some accumulation of cases in the extreme range. Girls were overrepresented in the extreme tactile defensiveness group. Both auditory and tactile defensiveness were modestly associated with fearful temperament and anxiety, but they were relatively distinct from other common dimensions of childhood behavioral dysfunction. Twin correlations for the full range of scores and concordance rates for the extremes suggested moderate genetic influences, with some indication that the tactile domain might be more heritable than the auditory domain.

Temperament and vagal tone in boys with fragile X syndrome

Physiological hyperarousal, an elevated state of physiological arousal and poor modulation, has been postulated to be a significant source of behavior problems in children with fragile X syndrome (FXS). Temperament has been associated with behavior problems and may also reflect biological reactivity. Young boys with FXS display poorly modulated and low levels of vagal tone (Roberts, Dev Psychobiol 2001;39:107-123) and high activity, poor attention, low adaptability, poor persistence, and low intensity when compared with a reference sample of typically developing (Hatton, Dev Med Child Neurol 1991;41:625-632). In this study, we integrated physiological indices of vagal tone with temperament ratings and compared a sample of 29 young boys with FXS to 31 typically developing boys matched on chronological age and ethnicity. Boys with FXS were more active, less adaptable, and less persistent than the comparison group. Boys with FXS also showed lower baseline levels and less suppression of vagal tone in response to changing task demands. A relationship between baseline vagal tone and persistence was shown across both groups. However, group differences in temperament dimensions did not appear to be mediated or moderated by vagal tone.

Neuropsychiatric symptoms of fragile X syndrome: pathophysiology and pharmacotherapy

Fragile X syndrome is the leading inherited form of mental retardation, and second only to Down's syndrome as a cause of mental retardation attributable to an identifiable genetic abnormality. Fragile X syndrome is caused by a defect in the fragile X mental retardation 1 gene (FMR1), located near the end of the long arm of the X chromosome. FMR1 normally synthesises the fragile X protein (FMRP), but mutations in FMR1 lead to a lack of FMRP synthesis, resulting in fragile X syndrome. While the specific function of FMRP is not yet fully understood, the protein is known to be important for normal brain development. The physical, cognitive and behavioural features of individuals with fragile X syndrome depend on gender (females have two X chromosomes, one active and one inactive) and the molecular status of the mutation (premutation, full mutation or mosaic). Features of the behavioural profile of individuals with fragile X syndrome include hypersensitivity to stimuli, overarousability, inattention, hyperactivity and (mostly in men) explosive and aggressive behaviour to others or self. Social anxiety, other anxiety disorders, depression, impulse control disorder and mood disorders are the most common psychiatric disorders diagnosed in individuals with fragile X syndrome, although no formal studies have been undertaken. There have been very few psychopharmacological studies of the treatment of behaviours associated with fragile X syndrome. These limited studies and surveys of psychotropic drugs used in individuals with fragile X syndrome suggest that stimulants are helpful for hyperactivity, that alpha(2)-adrenoceptor agonists and beta-adrenoceptor antagonists help to control overarousability, impulsivity and aggressiveness, and that SSRIs can control anxiety, impulsivity and irritability, alleviate depressive symptoms and decrease aggressive and self-injurious behaviour. Typical and atypical antipsychotics in combination with other psychotropics have been used for control of psychotic disorders and severe aggressive behaviours. Mood stabilisers have been found to be useful when mood dysregulation or mood disorders are present with or without aggressive behaviour. Folic acid and L-acetylcarnitine (levacecarnine) have not been found to improve deficits or behaviours. As there is no specific psychotropic drug for any of the deficits or behaviours associated with fragile X syndrome, clinicians are advised to diagnose any psychiatric syndromes or disorders present and treat them with the appropriate psychotropic drug. If no psychiatric disorder can be diagnosed and the patient's challenging behaviours cannot be controlled with environmental manipulation or behaviour modification techniques, the most benign psychotropic drug should be used. Antipsychotics should be reserved for psychotic disorders, for impulse control disorders (used in combination with other psychotropics), or when challenging behaviours constitute an emergency. In the future, new medications targeting molecules implicated in the modulation of anxiety, fear and fear responding will be useful for treating the social anxiety and overarousability exhibited by individuals with fragile X syndrome.

Early Intervention Practices and Communication Intervention Strategies for Young Males With Fragile X Syndrome

Purpose: This study describes speech-language pathologists’ impressions of the communication difficulties of young males with fragile X syndrome (FXS) and the need for both syndrome-specific and individualized interventions. The findings of a regional study that identified speech-language pathologists’ impressions of the speech, language, and behavioral difficulties experienced by males with FXS and an array of interventions used by speech-language pathologists to improve communication skills for these children are reported.

Methods: Fifty-one speech-language pathologists providing intervention for males with FXS ranging in age from 2 to 9 years (mean age=6;3 [years;months]) were interviewed.

Results: The majority of the speech-language pathologists reported that boys with FXS exhibit a visually based, experiential or wholistic learning preference. They emphasized the necessity of making environmental accommodations for limited attention span, difficulties with topic and activity transitions, sensory deficits, and low threshold for anxiety. They reported that speech goals focused on slowing rate and increasing precision for verbal children and both low and high levels of assistive technology for nonverbal or minimally verbal children. Language goals focused on listening, auditory comprehension, and narrative/conversation skills. Pragmatic goals emphasized social dialogue, role playing, and topic maintenance.

Clinical Implications: This study suggests that young males with FXS present the clinician with a constellation of behaviors and communication impairments that are both syndrome specific and symptom familiar. The specific communication strengths and deficits described by clinicians working with these children are common to many children with speech and language impairments compounded by cognitive deficits. Intervention programs for young boys with FXS should also attend closely to the specific behavioral (e.g., increased anxiety, attention deficits) and sensory "overload" problems they often exhibit before designing a tailored intervention program.

Self-injurious behavior in young boys with fragile X syndrome

In this study, we distributed surveys to 67 families of young boys with fragile X syndrome to determine the prevalence, onset, form, function, location, and correlates of self-injurious behavior. Fifty-five surveys were completed (82%). The mean age of the boys at the time of the survey was 80 months (range = 20-144). Self-injurious behavior (SIB) was reported for 58% of the participants with a mean age of onset of 31 months. The mean number of forms of self-injury was 2 per participant. Biting was the most commonly reported form of self-injury with the fingers and back of the hand disproportionately targeted as the most prevalent self-injury body site. There was no linear increase in risk of SIB with age past 25 months. SIB was reported as most likely to occur following the presentation of difficult task demands or changes in routine. Significant group differences were found between overall ratings of problem behavior for boys with self-injury compared to those without self-injury. Groups did not differ on measures of fragile X mental retardation protein (FMRP), autism status, adaptive behavior, or age first medicated. Results are discussed in terms of future research designed to further elucidate the behavioral phenotype of fragile X syndrome.

Cortisol and behavior in fragile X syndrome

OBJECTIVE

The purpose of this study was to determine if children with fragile X syndrome, who typically demonstrate a neurobehavioral phenotype that includes social anxiety, withdrawal, and hyper-arousal, have increased levels of cortisol, a hormone associated with stress. The relevance of adrenocortical activity to the fragile X phenotype also was examined.

METHOD

One hundred and nine children with the fragile X full mutation (70 males and 39 females) and their unaffected siblings (51 males and 58 females) completed an in-home evaluation including a cognitive assessment and a structured social challenge task. Multiple samples of salivary cortisol were collected throughout the evaluation day and on two typical non-school days. Measures of the fragile X mental retardation (FMR1) gene, child intelligence, the quality of the home environment, parental psychopathology, and the effectiveness of educational and therapeutic services also were collected. Linear mixed-effects analyses were used to examine differences in cortisol associated with the fragile X diagnosis and gender (fixed effects) and to estimate individual subject and familial variation (random effects) in cortisol hormone levels. Hierarchical multiple regression analyses were conducted to determine whether adrenocortical activity is associated with behavior problems after controlling for significant genetic and environmental factors.

RESULTS

Results showed that children with fragile X, especially males, had higher levels of salivary cortisol on typical days and during the evaluation. Highly significant family effects on salivary cortisol were detected, consistent with previous work documenting genetic and environmental influences on adrenocortical activity. Increased cortisol was significantly associated with behavior problems in boys and girls with fragile X but not in their unaffected siblings.

CONCLUSIONS

These results provide evidence that the function of the hypothalamic-pituitary-adrenal axis may have an independent association with behavioral problems in children with fragile X syndrome.

Genetic and environmental influences on the cognitive outcomes of children with fragile X syndrome

OBJECTIVE

To measure the genetic and environmental factors influencing the cognitive outcomes in children with fragile X, a common genetic disorder causing cognitive impairments.

METHOD

In-home evaluations were conducted on 120 children (80 boys and 40 girls) with the fragile X full mutation and their unaffected siblings.

RESULTS

Multiple regression analyses show that the cognitive outcomes for girls with fragile X are most strongly predicted by the mean IQ of their parents, with a small proportion of the variance accounted for by the quality of their home environment. FMR1 protein (FMRP) was associated with girls' levels of distractibility. Mean parental IQ was associated only with boys' Performance IQs, while FMRP was associated with boys' Full Scale IQs. The quality of boys' home environments accounted for more of the variance in their cognitive outcomes than it did for affected girls.

CONCLUSIONS

Both biological/genetic factors and environmental factors are significant predictors of IQ in children with fragile X syndrome; however, the influence of specific factors differs between girls and boys. These findings lay the foundation for further investigation into biological and environmental interventions.

The influence of environmental and genetic factors on behavior problems and autistic symptoms in boys and girls with fragile X syndrome

OBJECTIVE

Fragile X syndrome, caused by mutations in a single gene of the X chromosome (FMR1), is associated with neurobehavioral characteristics including social deficits with peers, social withdrawal, gaze aversion, inattention, hyperactivity, anxiety, depression, and autistic behavior. However, there is considerable variability in the behavioral and psychiatric problems among children with this condition. The purpose of this study was to measure genetic and environmental factors influencing behavior problems and autistic symptoms in children with fragile X syndrome.

DESIGN

We conducted an in-home evaluation of 120 children (80 boys and 40 girls) with the fragile X full mutation and their unaffected siblings, including measurements of the FMR1 protein (FMRP), quality of the home environment, maternal and paternal psychopathology, effectiveness of educational and therapeutic services, and child behavior problems.

RESULTS

Results of multiple regression analyses showed that for boys with fragile X, effectiveness of educational and therapeutic services and parental psychological problems predicted internalizing and externalizing types of problems, while the quality of the home environment predicted autistic behavior. For girls with fragile X, the results emphasized significant effects of FMRP on behavior, in particular social withdrawal and anxious/depressed behavior.

CONCLUSIONS

These findings are among the first to link FMRP expression to behavior. They also emphasize the significance of home- and school-based environmental variables in the neurobehavioral phenotype and help to lay the foundation for studies designed to identify specific interventions for reducing problem behavior in children with fragile X syndrome.

Cardiovascular indices of physiological arousal in boys with fragile X syndrome

In this study, the relationship between physiological arousal, as indexed by heart rate variability, was examined in boys with fragile X syndrome (FXS) and typically developing boys matched on chronological age. In addition, the relationship of heart activity to clinical and molecular factors in the group of boys with FXS was examined. Results suggest that boys with FXS have higher levels of heart activity during the passive phases, as reflected in shorter heart periods. This high level of heart activity appears to be due to increased sympathetic activity and reduced parasympathetic activity. Boys with FXS did not display the expected patterns of heart activity in response to phases of increasing challenge, and sympathetic and parasympathetic systems did not appear coordinated in these boys with FXS. Clinical factors may be related to neural regulation of heart activity while molecular factors do not appear to be.

Advances in research on the fragile X syndrome

Fragile X syndrome is a neurodevelopmental disorder that results from a single gene mutation on the X chromosome. The purpose of this review is to summarize key advances made in understanding the fragile X premutation gene seen in carriers and the full mutation gene seen in persons with the syndrome. DNA testing has replaced cytogenetic testing as the primary method for identification of fragile X, although the efficacy of protein level screening is being explored. The premutation is associated with no effects, although there is evidence of physical effects-primarily premature menopause and mild outward features of the fragile X syndrome-among premutation carriers. There is much controversy regarding premutation effects on psychological development. The few experimental studies carried out to date do not suggest noticeable or significant effects. One challenge in addressing this controversy is the sometimes ambiguous differentiation between premutation and full mutation genes. There is a well-established yet highly variable phenotype of the full mutation. Research from this decade has helped to address specific aspects of this phenotype, including the early course of its development in males, the influence of home and family environments, the nature of social difficulties and autistic features seen in boys and girls with fragile X, and the potential role of hyperarousal or hyper-reactivity. Studies in these areas, and on the role of FMR protein, will contribute towards ongoing advances in our understanding of fragile X syndrome and its mechanisms. The variability in physical, social, and cognitive features, as described in this review, is one that prohibits clear-cut screening guidelines designed to avoid high rates of both false positives and false negatives. Results from recent studies indicate the need to consider behavioral features in selecting candidates for fragile X screening. MRDD Research Reviews 2000;6:96-106.

Behavior and autonomic nervous system function assessed via heart period measures: the case of hyperarousal in boys with fragile X syndrome

Physiological responses may inform us about and help us to interpret behavioral responses. For example, hyperarousal may be a source of behavior problems in children with fragile X syndrome (FXS). To evaluate this approach, we examined heart period data in specific contexts in boys with FXS and in normally developing chronological-age-matched boys. Spectral analysis was used to evaluate the parasympathetic and sympathetic nervous systems' contributions to heart period. Boys with FXS had shorter interbeat intervals, lower parasympathetic activity, and similar sympathetic activity. Also, the groups were differentially responsive to experimental challenge. These results have important implications for our understanding of the basic nervous system dysfunction in FXS and for the strategies likely to be effective in terms of pharmacological intervention with these children. These methods can be applied to a variety of contexts and populations, including children who are sensory defensive, socially avoidant, inattentive, or hyperactive.