Annotation: Deconstructing the attention deficit in fragile X syndrome: a developmental neuropsychological approach

Assessing Children's Executive Function: BADS-C Validity

OBJECTIVES

To investigate the external and ecological validity of a standardized test of children's executive functioning (EF), the Behavioral Assessment of the Dysexecutive Syndrome for Children (BADS-C).

BACKGROUND

There are few standardized measures for assessing executive functions in children, and the evidence for the validity of most measures is currently limited.

METHOD

A normative sample of 256 children and adolescents from age 8-16 years completed the BADS-C, and a parent or teacher completed rating scales of the child's everyday problems related to EF (Children's version of the Dysexecutive Questionnaire; DEX-C) and Strengths and Difficulties Questionnaire (SDQ), a commonly used measure of emotional, social, cognitive, and behavioral problems.

RESULTS

Exploratory factor analyses yielded a two-factor structure to the BADS-C, indicative of monitoring and abstract reasoning processes, and a three-factor structure to the DEX-C, reflecting behavioral, and cognitive components of the dysexecutive syndrome as well as emotional responsiveness. Regression analyses showed significant relationships between BADS-C scores and everyday functioning as reported on the DEX and SDQ. Furthermore, there were significant differences in BADS-C scores between those children in the upper and lower quartiles on the SDQ.

CONCLUSION

Results provide tentative evidence of BADS-C and DEX-C construct, convergent and predictive validity.

Telehealth-enabled behavioral treatment for problem behaviors in boys with fragile X syndrome: a randomized controlled trial

Background

Children with fragile X syndrome (FXS) are at increased risk for exhibiting problem behaviors such as aggression and self-injury. However, many children with FXS have limited access to behavioral treatments that have known efficacy due to the low availability of treatment providers and the wide geographical dispersion of families with FXS across the country. Telehealth may offer a cost-effective and practical solution to overcome these significant barriers. We examined the effect of administering an established behavior analytic intervention called functional communication training (FCT) via telehealth on levels of problem behaviors exhibited by boys with FXS. We also examined treatment acceptability, as well as the effect of the treatment on levels of parenting stress.

Methods

Boys with FXS, aged 3 to 10 years, who displayed problem behaviors daily, were randomized to receive FCT via telehealth (n = 30) or treatment as usual (n = 27) over 12 weeks. Outcome measures included in-session observations of problem behavior, the Aberrant Behavior Checklist—Community (ABC-C), the Treatment Acceptability Rating Form—Revised (TARF-R), and the Parenting Stress Index, 4th edition (PSI-4).

Results

Intention-to-treat analyses indicated that scores on the irritability subscale of the ABC-C, our primary outcome measure, decreased significantly for boys who received FCT via telehealth compared to boys who received treatment as usual (p < .001, Cohen’s d = 0.65). In-session observations conducted for those who received treatment showed that levels of problem behavior decreased by 91% from baseline. Levels of parenting stress related to child behavioral problems were also lower following FCT treatment, and caregivers reported that the intervention was acceptable.

Conclusions

These findings support telehealth-enabled FCT as a framework for expanding access to behavioral treatments for problem behaviors in children with FXS. Expanded delivery of behavior analytic treatment via telehealth also has the potential to lower healthcare costs, improve child and family quality of life, and lead to advances in the treatment of problem behavior in the broader population of individuals with neurodevelopmental disorders.

Trial registration

ClinicalTrials.gov, NCT03510156. Registered 27 April 2018

Expressed emotion and impulsiveness in mothers of children with Fragile X Syndrome and Down Syndrome: The relation to behavioral problems in their offspring

BACKGROUND

Fragile X Syndrome (FXS) and Down Syndrome (DS) are common causes of Intellectual Disability (ID). Mothers of individuals with FXS sometimes have the premutation condition which makes them display neurocognitive signs, such as impulsiveness impairments, while mothers of DS individuals, as a group, do not have impairments. Although behavior problems in individuals with ID may be related to high Expressed Emotion (EE) in parents, parenting in families with ID members has been little explored.

AIM

To explore the relationship between a mother's EE and impulsiveness, in mothers of individuals with FXS and DS, with behavior problems in their offspring.

METHOD

A questionnaire was developed to collect data about impulsiveness and EE in mothers, along with information about behavior problems in ID individuals.

RESULTS

EE scores were associated with behavior problems in their offspring for both samples. Mothers with the premutation showed higher scores in EE than mothers of DS individuals. However, impulsiveness scores were not different between both parental groups, and were related to EE scores.

CONCLUSIONS

EE is a parental feature that is possible to modulate and seems to be related to behavior problems in ID individuals. More research should be carried on to create interventions to reduce this attitude in parents of ID individuals.

Characterization of ultrasonic vocalizations of Fragile X mice

Fragile X Syndrome (FXS) is the leading form of inherited intellectual disability. It is caused by the transcriptional silencing of FMR1, the gene which codes for the Fragile X Mental Retardation Protein (FMRP). Patients who have FXS exhibit numerous behavioral and cognitive impairments, such as attention-deficit/hyperactivity disorder, obsessive compulsive disorder, and autistic-like behaviors. In addition to these behavioral abnormalities, FXS patients have also been shown to exhibit various deficits in communication such as abnormal sentence structures, increased utterances, repetition of sounds and words, and reduced articulation. These deficits can dramatically hinder communication for FXS patients, exacerbating learning and cognition impairments while decreasing their quality of life. To examine the biological underpinnings of these communication abnormalities, studies have used a mouse model of the Fragile X Syndrome; however, these vocalization studies have resulted in inconsistent findings that often do not correlate with abnormalities observed in FXS patients. Interestingly, a detailed examination of frequency modulated vocalizations that are believed to be a better assessment of rodent communication has never been conducted. The following study used courtship separation to conduct a detailed examination of frequency modulated ultrasonic vocalizations (USV) in FXS mice. Our analyses of frequency modulated USVs demonstrated that adult FXS mice exhibited longer phrases and more motifs. Phrases are vocalizations consisting of multiple frequency modulated ultrasonic vocalizations, while motifs are repeated frequency modulated USV patterns. Fragile X mice had a higher proportion of "u" syllables in all USVs and phrases while their wildtype counterparts preferred isolated "h" syllables. Although the specific importance of these syllables towards communication deficits still needs to be evaluated, these findings in production of USVs are consistent with the repetitive and perseverative speech patterns observed in FXS patients. This study demonstrates that FXS mice can be used to study the underlying biological mechanism(s) mediating FXS vocalization abnormalities.

Profiles of aberrant white matter microstructure in fragile X syndrome

Previous studies attempting to quantify white matter (WM) microstructure in individuals with fragile X syndrome (FXS) have produced inconsistent findings, most likely due to the various control groups employed, differing analysis methods, and failure to examine for potential motion artifact. In addition, analyses have heretofore lacked sufficient specificity to provide regional information. In this study, we used Automated Fiber-tract Quantification (AFQ) to identify specific regions of aberrant WM microstructure along WM tracts in patients with FXS that differed from controls who were matched on age, IQ and degree of autistic symptoms. Participants were 20 patients with FXS, aged 10 to 23 years, and 20 matched controls. Using Automated Fiber-tract Quantification (AFQ), we created Tract Profiles of fractional anisotropy and mean diffusivity along 18 major WM fascicles. We found that fractional anisotropy was significantly increased in the left and right inferior longitudinal fasciculus (ILF), right uncinate fasciculus, and left cingulum hippocampus in individuals with FXS compared to controls. Conversely, mean diffusivity was significantly decreased in the right ILF in patients with FXS compared to controls. Age was significantly negatively associated with MD values across both groups in 11 tracts. Taken together, these findings indicate that FXS results in abnormal WM microstructure in specific regions of the ILF and uncinate fasciculus, most likely caused by inefficient synaptic pruning as a result of decreased or absent Fragile X Mental Retardation Protein (FMRP). Longitudinal studies are needed to confirm these findings.

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.

Concurrent Relations between Face Scanning and Language: A Cross-Syndrome Infant Study

Typically developing (TD) infants enhance their learning of spoken language by observing speakers' mouth movements. Given the fact that word learning is seriously delayed in most children with neurodevelopmental disorders, we hypothesized that this delay partly results from differences in visual face scanning, e.g., focusing attention away from the mouth. To test this hypothesis, we used an eye tracker to measure visual attention in 95 infants and toddlers with Down syndrome (DS), fragile X syndrome (FXS), and Williams syndrome (WS), and compared their data to 25 chronological- and mental-age matched 16-month-old TD controls. We presented participants with two talking faces (one on each side of the screen) and a sound (/ga/). One face (the congruent face) mouthed the syllable that the participants could hear (i.e., /ga/), while the other face (the incongruent face) mouthed a different syllable (/ba/) from the one they could hear. As expected, we found that TD children with a relatively large vocabulary made more fixations to the mouth region of the incongruent face than elsewhere. However, toddlers with FXS or WS who had a relatively large receptive vocabulary made more fixations to the eyes (rather than the mouth) of the incongruent face. In DS, by contrast, fixations to the speaker's overall face (rather than to her eyes or mouth) predicted vocabulary size. These findings suggest that, at some point in development, different processes or strategies relating to visual attention are involved in language acquisition in DS, FXS, and WS. This knowledge may help further explain why language is delayed in children with neurodevelopmental disorders. It also raises the possibility that syndrome-specific interventions should include an early focus on efficient face-scanning behaviour.

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.

Anxiety, hyperactivity and stereotypy in a zebrafish model of fragile X syndrome and autism spectrum disorder

Fragile X syndrome (FXS) is the most common form of inherited intellectual disability and is caused by a loss of function of the fragile X mental retardation (fmr1) gene. Animal fmr1-knockout (KO) models are not only of interest for the study of FXS, but have also important implications for our understanding of autism spectrum disorder (ASD). Here we report the behavioral changes in fmr1-knockout zebrafish in an open field with two white and two transparent walls. The neophobic responses that in wild-type (WT) zebrafish normally occur during the first 5-10 min in an unfamiliar environment (such as freezing, hypo-activity and preferences for the bottom and opaque walls of the tank), were weakened in fmr1 mutants, suggesting a reduction of novelty-induced anxiety. The fmr1-KO zebrafish showed somewhat increased vertical activity beyond the 'neophobic phase', but no overall hyperactivity. The mutants demonstrated a clear habituation-independent preference for the transparent walls. Whether this was attributable to altered spatial information processing or to reduced avoidance of open spaces is discussed. Finally, since restrictive repetitive (or stereotypical) behaviors are frequently present in FXS and ASD patients, we analyzed relative turning angles, directional and preferential turning ratios and performed frequency-domain analysis. However, no indications of abnormal movement patterning were detected. The possible reasons for the absence of stereotypical behaviors are discussed in terms of behavioral endpoint selection and of eliciting conditions. Overall, our findings are consistent with those reported in fmr1-KO mice and suggest that further analysis of the fmr1-KO zebrafish model has potential to deepen our understanding of FXS and ASD.

Using discrete trial training to identify specific learning impairments in boys with fragile X syndrome

We examined whether discrete trial training (DTT) could be used to identify learning impairments in mathematical reasoning in boys with fragile X syndrome (FXS). Boys with FXS, aged 10-23 years, and age and IQ-matched controls, were trained to match fractions to pie-charts and pie-charts to decimals either on a computer or with a trained behavior analyst using DTT. Participants with FXS obtained significantly lower learning rates on the fractions to pie-charts task, and were more likely to perseverate on previously reinforced responses during learning compared to controls. These data suggest that DTT can be used to identify specific learning impairments in boys with FXS, as well as other low-functioning individuals with developmental disabilities.

The fragile X syndrome-autism comorbidity: what do we really know?

Autism spectrum disorder (ASD) is a common comorbid condition in people with fragile X syndrome (FXS). It has been assumed that ASD symptoms reflect the same underlying psychological and neurobiological impairments in both FXS and non-syndromic ASD, which has led to the claim that targeted pharmaceutical treatments that are efficacious for core symptoms of FXS are likely to be beneficial for non-syndromic ASD as well. In contrast, we present evidence from a variety of sources suggesting that there are important differences in ASD symptoms, behavioral and psychiatric correlates, and developmental trajectories between individuals with comorbid FXS and ASD and those with non-syndromic ASD. We also present evidence suggesting that social impairments may not distinguish individuals with FXS with and without ASD. Finally, we present data that demonstrate that the neurobiological substrates of the behavioral impairments, including those reflecting core ASD symptoms, are different in FXS and non-syndromic ASD. Together, these data suggest that there are clinically important differences between FXS and non-syndromic ASD that are masked by reliance on the categorical diagnosis of ASD. We argue for use of a symptom-based approach in future research, including studies designed to evaluate treatment efficacy.

Rule-based category learning in Down syndrome

Rule-based category learning was examined in youths with Down syndrome (DS), youths with intellectual disability (ID), and typically developing (TD) youths. Two tasks measured category learning: the Modified Card Sort task (MCST) and the Concept Formation test of the Woodcock-Johnson-III ( Woodock, McGrew, & Mather, 2001 ). In regression-based analyses, DS and ID groups performed below the level expected for their nonverbal ability. In cross-sectional developmental trajectory analyses, results depended on the task. On the MCST, the DS and ID groups were similar to the TD group. On the Concept Formation test, the DS group had slower cross-sectional change than the other 2 groups. Category learning may be an area of difficulty for those with ID, but task-related factors may affect trajectories for youths with DS.

A neurodevelopmental perspective on the acquisition of nonverbal cognitive skills in adolescents with fragile X syndrome

This longitudinal study was designed to investigate trajectories of nonverbal cognitive ability in adolescents with fragile X syndrome with respect to the relative influence of fragile X mental retardation protein (FMRP), autism symptom severity, and environmental factors on visualization and fluid reasoning abilities. Males and females with fragile X syndrome (N = 53; ages 10-16 years) were evaluated with the Leiter-R at up to four annual assessments. On average, IQ declined with age. FMRP levels predicted change in fluid reasoning, but not in visualization. The role of FMRP in the neural development that underlies the fragile X syndrome cognitive phenotype is discussed.

Common and specific impairments in attention functioning in girls with chromosome 22q11.2 deletion, fragile X or Turner syndromes

Background

Chromosome 22q11.2 deletion syndrome (22q11.2DS), fragile X syndrome (FXS), and Turner syndrome (TS) are complex and variable developmental syndromes caused by different genetic abnormalities; yet, they share similar cognitive impairments in the domains of numbers, space, and time. The atypical development of foundational neural networks that underpin the attentional system is thought to result in further impairments in higher-order cognitive functions. The current study investigates whether children with similar higher-order cognitive impairments but different genetic disorders also show similar impairments in alerting, orienting, and executive control of attention.

Methods

Girls with 22q11.2DS, FXS, or TS and typically developing (TD) girls, aged 7 to 15 years, completed an attention network test, a flanker task with alerting and orienting cues. Exploration of reaction times and accuracy allowed us to test for potential commonalities in attentional functioning in alerting, orienting, and executive control. Linear regression models were used to test whether the predictors of group and chronological age were able to predict differences in attention indices.

Results

Girls with 22q11.2DS, FXS, or TS demonstrated unimpaired function of the alerting system and impaired function of the executive control system. Diagnosis-specific impairments were found such that girls with FXS made more errors and had a reduced orienting index, while girls with 22q11.2DS showed specific age-related deficits in the executive control system.

Conclusions

These results suggest that the control but not the implementation of attention is selectively impaired in girls with 22q11.2DS, TS or FXS. Additionally, the age effect on executive control in girls with 22q11.2DS implies a possible altered developmental trajectory.

Social approach and emotion recognition in fragile X syndrome

Evidence is emerging that individuals with Fragile X syndrome (FXS) display emotion recognition deficits, which may contribute to their significant social difficulties. The current study investigated the emotion recognition abilities, and social approachability judgments, of FXS individuals when processing emotional stimuli. Relative to chronological age- (CA-) and mental age- (MA-) matched controls, the FXS group performed significantly more poorly on the emotion recognition tasks, and displayed a bias towards detecting negative emotions. Moreover, after controlling for emotion recognition deficits, the FXS group displayed significantly reduced ratings of social approachability. These findings suggest that a social anxiety pattern, rather than poor socioemotional processing, may best explain the social avoidance observed in FXS.

Viewing social scenes: a visual scan-path study comparing fragile X syndrome and Williams syndrome

Fragile X syndrome (FXS) and Williams syndrome (WS) are both genetic disorders which present with similar cognitive-behavioral problems, but distinct social phenotypes. Despite these social differences both syndromes display poor social relations which may result from abnormal social processing. This study aimed to manipulate the location of socially salient information within scenes to investigate the visual attentional mechanisms of: capture, disengagement, and/or general engagement. Findings revealed that individuals with FXS avoid social information presented centrally, at least initially. The WS findings, on the other hand, provided some evidence that difficulties with attentional disengagement, rather than attentional capture, may play a role in the WS social phenotype. These findings are discussed in relation to the distinct social phenotypes of these two disorders.

Biobehavioral indicators of social fear in young children with fragile X syndrome

Anxiety is among the most impairing conditions associated with Fragile X syndrome (FXS) and is putatively linked to atypical physiological arousal. However, few studies have examined this association in young children with FXS. The authors examined whether patterns of arousal and behavior during an experimental stranger approach paradigm differ between a cross-sectional sample of 21 young children with FXS and 19 controls (12-58 months old). Groups did not differ in mean levels of behavioral fear. Unlike the control group, however, the FXS group demonstrated increased facial fear at older ages, as well as age-dependent changes in associations between heart activity and distress vocalizations. These findings may inform theoretical models of anxiety etiology in FXS and early detection efforts.

Ontogeny of contextual fear memory formation, specificity, and persistence in mice

Pinpointing the precise age when young animals begin to form memories of aversive events is valuable for understanding the onset of anxiety and mood disorders and for detecting early cognitive impairment in models of childhood-onset disorders. Although these disorders are most commonly modeled in mice, we know little regarding the development of learning and memory in this species because most previous studies have been restricted to rats. Therefore, in the present study, we constructed an ontogenetic timeline of contextual fear memory ranging from infancy to adulthood in mice. We found that the ability of mice to form long-term context-shock associations emerged ∼13-14 d of age, which is several days earlier than previously reported for rats. Although the ability to form contextual fear memories remained stable from infancy into adulthood, infant mice had shorter-lasting memories than adolescent and adult mice. Furthermore, we found that mice subjected to fetal alcohol exposure showed a delay in the developmental emergence of contextual fear memory, illustrating the utility of this ontogenetic approach in detecting developmental delays in cognitive function stemming from maladaptive early life experience.

A 'learning platform' approach to outcome measurement in fragile X syndrome: a preliminary psychometric study

BACKGROUND

Clinical trials of medications to alleviate the cognitive and behavioural symptoms of individuals with fragile X syndrome (FXS) are now underway. However, there are few reliable, valid and/or sensitive outcome measures available that can be directly administered to individuals with FXS. The majority of assessments employed in clinical trials may be suboptimal for individuals with intellectual disability (ID) because they require face-to-face interaction with an examiner, taxing administration periods, and do not provide reinforcement and/or feedback during the test. We therefore examined the psychometric properties of a new computerised 'learning platform' approach to outcome measurement in FXS.

METHOD

A brief computerised test, incorporated into the Discrete Trial Trainer©- a commercially available software program designed for children with ID - was administered to 13 girls with FXS, 12 boys with FXS and 15 matched ID controls aged 10 to 23 years (mental age = 4 to 12 years). The software delivered automated contingent access to reinforcement, feedback, token delivery and prompting procedures (if necessary) on each trial to facilitate responding. The primary outcome measure was the participant's learning rate, derived from the participant's cumulative record of correct responses.

RESULTS

All participants were able to complete the test and floor effects appeared to be minimal. Learning rates averaged approximately five correct responses per minute, ranging from one to eight correct responses per minute in each group. Test-retest reliability of the learning rates was 0.77 for girls with FXS, 0.90 for boys with FXS and 0.90 for matched ID controls. Concurrent validity with raw scores obtained on the Arithmetic subtest of the Wechsler Intelligence Scale for Children-III was 0.35 for girls with FXS, 0.80 for boys with FXS and 0.56 for matched ID controls. The learning rates were also highly sensitive to change, with effect sizes of 1.21, 0.89 and 1.47 in each group respectively following 15 to 20, 15-min sessions of intensive discrete trial training conducted over 1.5 days.

CONCLUSIONS

These results suggest that a learning platform approach to outcome measurement could provide investigators with a reliable, valid and highly sensitive measure to evaluate treatment efficacy, not only for individuals with FXS but also for individuals with other ID.

Comprehensive neurocognitive endophenotyping strategies for mouse models of genetic disorders

There is a need for refinement of the current behavioral phenotyping methods for mouse models of genetic disorders. The current approach is to perform a behavioral screen using standardized tasks to define a broad phenotype of the model. This phenotype is then compared to what is known concerning the disorder being modeled. The weakness inherent in this approach is twofold: First, the tasks that make up these standard behavioral screens do not model specific behaviors associated with a given genetic mutation but rather phenotypes affected in various genetic disorders; secondly, these behavioral tasks are insufficiently sensitive to identify subtle phenotypes. An alternate phenotyping strategy is to determine the core behavioral phenotypes of the genetic disorder being studied and develop behavioral tasks to evaluate specific hypotheses concerning the behavioral consequences of the genetic mutation. This approach emphasizes direct comparisons between the mouse and human that facilitate the development of neurobehavioral biomarkers or quantitative outcome measures for studies of genetic disorders across species.

Effects of computerized match-to-sample training on emergent fraction-decimal relations in individuals with fragile X syndrome

Individuals diagnosed with fragile X syndrome (FXS), the most common known form of inherited intellectual disability, are reported to exhibit considerable deficits in mathematical skills that are often attributed to brain-based abnormalities associated with the syndrome. We examined whether participants with FXS would display emergent fraction-decimal relations following brief, intensive match-to-sample training on baseline relations. The performance profiles on tests of symmetry and transitivity/equivalence of 11 participants with FXS, aged 10-23 years, following baseline match-to-sample training were compared to those of 11 age- and IQ-matched controls with idiopathic developmental disability. The results showed that both groups of participants showed significant improvements in the baseline (trained) relations, as expected. However, participants with FXS failed to show significant improvements in the (untrained) symmetry and transitivity/equivalence relations compared to those in the control group. A categorical analysis of the data indicated that five participants with FXS and eight controls showed at least "intermediate" emergence of symmetry relations, whereas one individual with FXS and three controls showed at least intermediate emergence of transitivity/equivalence relations. A correlation analysis of the data indicated that improvements in the symmetry relations were significantly associated with improvements in the transitivity/equivalence relations in the control group (r=.69, p=.018), but this was not the case in the FXS group (r=.34, p>.05). Participant IQ was significantly associated with improvements in the symmetry relations in individuals with FXS (r=.60, p=.049), but not in controls (r=.21, p>.05). Taken together, these results suggest that brief, computerized match-to-sample training may produce emergent mathematical relations for a subset of children with FXS and developmental disabilities. However, the ability of individuals with FXS to form transitivity/equivalence relations may be impaired relative to those with idiopathic developmental disabilities, which may be attributed to neurodevelopmental variables associated with the syndrome.

Fragile X syndrome and targeted treatment trials

Work in recent years has revealed an abundance of possible new treatment targets for fragile X syndrome (FXS). The use of animal models, including the fragile X knockout mouse which manifests a phenotype very similar to FXS in humans, has resulted in great strides in this direction of research. The lack of Fragile X Mental Retardation Protein (FMRP) in FXS causes dysregulation and usually overexpression of a number of its target genes, which can cause imbalances of neurotransmission and deficits in synaptic plasticity. The use of metabotropic glutamate receptor (mGluR) blockers and gamma amino-butyric acid (GABA) agonists have been shown to be efficacious in reversing cellular and behavioral phenotypes, and restoring proper brain connectivity in the mouse and fly models. Proposed new pharmacological treatments and educational interventions are discussed in this chapter. In combination, these various targeted treatments show promising preliminary results in mitigating or even reversing the neurobiological abnormalities caused by loss of FMRP, with possible translational applications to other neurodevelopmental disorders including autism.

Delineation of behavioral phenotypes in genetic syndromes: characteristics of autism spectrum disorder, affect and hyperactivity

We investigated autism spectrum disorder (ASD) symptomatology, hyperactivity and affect in seven genetic syndromes; Angelman (AS; n = 104), Cri du Chat (CdCS; 58), Cornelia de Lange (CdLS; 101), Fragile X (FXS; 191), Prader-Willi (PWS; 189), Smith-Magenis (SMS; 42) and Lowe (LS; 56) syndromes (age range 4-51). ASD symptomatology was heightened in CdLS and FXS. High levels of impulsivity were seen in SMS, AS, CdCS, FXS and adults with CdLS. Negative affect was prominent in adults with CdLS, while positive affect was prominent in adults with AS and FXS. Heightened levels of overactivity and impulsivity were identified in FXS, AS and SMS while low levels were identified in PWS. These findings confirm and extend previously reported behavioral phenotypes.

The GABA(A) receptor agonist THIP ameliorates specific behavioral deficits in the mouse model of fragile X syndrome

Hyperactivity, hypersensitivity to auditory stimuli, and exaggerated fear are common behavioral abnormalities observed in individuals with fragile X syndrome (FXS), a neurodevelopmental disorder that is the most common genetic cause of autism. Evidence from studies of the Fmr1 knockout (KO) mouse model of FXS supports the notion that impaired GABAergic transmission in different brain regions such as the amygdala, striatum or cerebral cortex is central to FXS behavioral abnormalities. This suggests that the GABAergic system might be an intriguing target to ameliorate some of the phenotypes in FXS. Our recent work revealed that THIP (gaboxadol), a GABA(A) receptor agonist, can restore principal neuron excitability deficits in the Fmr1 KO amygdala, suggesting that THIP may also restore some of the key behavioral abnormalities in Fmr1 KO mice. Here, we reveal that THIP significantly attenuated hyperactivity in Fmr1 KO mice, and reduced prepulse inhibition in a volume-dependent manner. In contrast, THIP did not reverse the deficits in cued fear or startle response. Thus, this study shows that enhancing GABAergic transmission can correct specific behavioral phenotypes of the Fmr1 KO mouse further supporting that targeting the GABAergic system, and specifically tonic inhibition, might be important for correcting or ameliorating some key behaviors in FXS.

Fragile X syndrome: lifespan developmental implications for those without as well as with intellectual disability

PURPOSE OF REVIEW

Advances in developmental neuropsychiatry and the mental health needs of people with intellectual disability are creating ever greater understanding of the critical associations between human genome variations and psychological functioning throughout lifespan and across the entire intellectual ability spectrum. This review highlights the recent developments and their clinical implications for people with fragile X syndrome.

RECENT FINDINGS

There is substantial evidence for individuals of all ages and intellectual abilities being prone to psychological profiles determined not only by having a fragile X gene full mutation, but also by having premutations and intermediate alleles. The importance of these genetic contributors to mental life, if anything, increases with age. Premutation carriers are prone to neurodegenerative mid-life fragile X tremor-ataxia syndrome. Women with premutations experience premature ovarian insufficiency. Imbalances in the (gamma amino butyrie acid)-glutamate mediated postsynaptic cascade central neuronal pathways are a current focus of psychopharmacological enquiry, giving the hope of syndrome-specific medical treatments.

SUMMARY

Findings from genetic, neurological, biochemical, psychological and pharmacological research are combining to revolutionize understanding of the pathogenesis of developmental and psychological disabilities affecting individuals with fragile X syndrome irrespective of age, intelligence level and gene mutation status. Results of syndrome-specific medication trials are awaited.

What can we learn about autism from studying fragile X syndrome?

Despite early controversy, it is now accepted that a substantial proportion of children with fragile X syndrome (FXS) meets diagnostic criteria for autism spectrum disorder (ASD). This change has led to an increased interest in studying the association of FXS and ASD because of the clinical consequences of their co-occurrence and the implications for a better understanding of ASD in the general population. Here, we review the current knowledge on the behavioral, neurobiological (i.e., neuroimaging), and molecular features of ASD in FXS, as well as the insight into ASD gained from mouse models of FXS. This review covers critical issues such as the selectivity of ASD in disorders associated with intellectual disability, differences between autistic features and ASD diagnosis, and the relationship between ASD and anxiety in FXS patients and animal models. While solid evidence supporting ASD in FXS as a distinctive entity is emerging, neurobiological and molecular data are still scarce. Animal model studies have not been particularly revealing about ASD in FXS either. Nevertheless, recent studies provide intriguing new leads and suggest that a better understanding of the bases of ASD will require the integration of multidisciplinary data from FXS and other genetic disorders.

Top-down or bottom-up: Contrasting perspectives on psychiatric diagnoses

Clinical psychiatry is confronted with the expanding knowledge of medical genetics. Most of the research into the genetic underpinnings of major mental disorders as described in the categorical taxonomies, however, did reveal linkage with a variety of chromosomes. This heterogeneity of results is most probably due to the assumption that the nosological categories as used in these studies are disease entities with clear boundaries. If the reverse way of looking, the so-called bottom-up approach, is applied, it becomes clear that genetic abnormalities are in most cases not associated with a single psychiatric disorder but with a certain probability to develop a variety of aspecific psychiatric symptoms. The adequacy of the categorical taxonomy, the so-called top-down approach, seems to be inversely related to the amount of empirical etiological data. This is illustrated by four rather prevalent genetic syndromes, fragile X syndrome, Prader-Willi syndrome, 22q11 deletion syndrome, and Noonan syndrome, as well as by some cases with rare chromosomal abnormalities. From these examples, it becomes clear that psychotic symptoms as well as mood, anxiety, and autistic features can be found in a great variety of different genetic syndromes. A psychiatric phenotype exists, but comprises, apart from the chance to present several psychiatric symptoms, all elements from developmental, neurocognitive, and physical characteristics.

Motor deficits on a ladder rung task in male and female adolescent and adult CGG knock-in mice

The fragile X premutation is a tandem CGG trinucleotide repeat expansion on the FMR1 gene between 55 and 200 repeats in length. A CGG knock-in (CGG KI) mouse with CGG trinucleotide repeat lengths between 70 and 350 has been developed and used to model the histopathology and cognitive deficits reported in carriers of the fragile X premutation. Previous studies have shown that CGG KI mice show progressive deficits in processing spatial and temporal information. To characterize the motor deficits associated with the fragile X premutation, male and female CGG KI mice ranging from 2 to 16 months of age with trinucleotide repeats ranging from 72 to 240 CGG in length were tested for their ability to perform a skilled ladder rung walking test. The results demonstrate that both male and female CGG KI mice showed a greater number of foot slips as a function of increased CGG repeat length, independent of the age of the animal or general activity level.

Using perceptual signatures to define and dissociate condition-specific neural etiology: autism and fragile X syndrome as model conditions

The functional link between genetic alteration and behavioral end-state is rarely straightforward and never linear. Cases where neurodevelopmental conditions defined by a distinct genetic etiology share behavioral phenotypes are exemplary, as is the case for autism and Fragile X Syndrome (FXS). In this paper and its companion paper, we propose a method for assessing the functional link between genotype and neural alteration across these target conditions by comparing their perceptual signatures. In the present paper, we discuss how such signatures can be used to (1) define and differentiate various aspects of neural functioning in autism and FXS, and subsequently, (2) to infer candidate causal (genetic) mechanisms based on such signatures (see companion paper, this issue).

Autism-lessons from the X chromosome

Recognized cases of autism spectrum disorders are on the rise. It is unclear whether this increase is attributable to secular trends in biological susceptibility, or to a change in diagnostic practices and recognition. One hint concerning etiological influences is the universally reported male excess (in the range of 4:1 to 10:1). Evidence suggests that genetic influences from the X chromosome play a crucial role in engendering this male vulnerability. In this review, we discuss three categories of genetic disease that highlight the importance of X-linked genes in the manifestation of an autistic phenotype: aneuploides (Turner syndrome and Klinefelter syndrome), trinucleotide expansions (Fragile X syndrome) and nucleotide mutations (Rett Syndrome, Neuroligins 3 & 4, and SLC6A8). The lessons from these diseases include an understanding of autistic features as a broad phenotype rather than as a single clinical entity, the role of multiple genes either alone or in concert with the manifestation of autistic features, and the role of epigenetic factors such as imprinting and X-inactivation in the expression of disease severity. Better understanding of the clinical phenotypes of social cognition and the molecular neurogenetics of X-linked gene disorders will certainly provide additional tools for understanding autism in the years to come.

Fragile X syndrome -- from genes to cognition

Fragile X syndrome (FXS), a single gene disorder with an expanded CGG allele on the X chromosome, is the most common form of inherited cognitive impairment. The cognitive deficit ranges from mild learning disabilities to severe intellectual disability. The phenotype includes hyperactivity, short attention span, emotional problems including anxiety, social avoidance, poor eye contact, and hyperarousal to sensory stimuli. Imaging studies in FXS have clarified the impact of the FMR1 mutation on brain development and function by documenting structural abnormalities, predominantly in the caudate nucleus and cerebellum, and functional deficits in the caudate, frontal-striatal circuits, and the limbic system. On the basis of current research results, a targeted treatment for FXS will be available in the near future. Currently, a number of psychopharmacological agents are helpful in treating many of the problems in FXS including hyperactivity, attention deficits, anxiety, episodic aggression, and hyperarousal. Although the targeted treatments aim at strengthening synaptic connections, it is essential that these treatments are combined with learning programs that address the cognitive deficits in FXS.

Gender differences in neurodevelopmental disorders: autism and fragile x syndrome

Gender is an important factor to consider in understanding the clinical presentation, management, and developmental trajectory of children with neuropsychiatric disorders. While much is known about the clinical and neurobehavioural profiles of boys with neuropsychiatric disorders, surprisingly little is known about girls. The aim of this chapter was to review our understanding of gender by considering the most prevalent childhood onset neuropsychiatric disorders, autism and Fragile X syndrome. This chapter highlights findings which suggest that girls with autism and Fragile X syndrome show some unique differences in cognitive and clinical profiles when compared to boys with these conditions; this may indicate the need for innovative assessment and management approaches which take gender into consideration. Our understanding of how differences emerge in boys and girls with neuropsychiatric disorders is unclear, future research needs to focus on the role of biological maturation rates, sex hormones, and psychosocial factors in order to progress this field.

Insights into brain development from neurogenetic syndromes: evidence from fragile X syndrome, Williams syndrome, Turner syndrome and velocardiofacial syndrome

Over the past few decades, behavioral, neuroimaging and molecular studies of neurogenetic conditions, such as Williams, fragile X, Turner and velocardiofacial (22q11.2 deletion) syndromes, have led to important insights regarding brain development. These investigations allow researchers to examine "experiments of nature" in which the deletion or alteration of one gene or a contiguous set of genes can be linked to aberrant brain structure or function. Converging evidence across multiple imaging modalities has now begun to highlight the abnormal neural circuitry characterizing many individual neurogenetic syndromes. Furthermore, there has been renewed interest in combining analyses across neurogenetic conditions in order to search for common organizing principles in development. In this review, we highlight converging evidence across syndromes from multiple neuroimaging modalities, with a particular emphasis on functional imaging. In addition, we discuss the commonalities and differences pertaining to selective deficits in visuospatial processing that occur across four neurogenetic syndromes. We suggest avenues for future exploration, with the goal of achieving a deeper understanding of the neural abnormalities in these affected populations.

Functional skills of individuals with fragile x syndrome: a lifespan cross-sectional analysis

Parents of 1,105 male and 283 female children with fragile X syndrome described functional skill attainment in eating, dressing, toileting, bathing/hygiene, communication, articulation, and reading. The majority of adult children had mastered many skills independently. Most adults were verbal, used the toilet, dressed, ate independently, bathed, and used a towel independently. However, some skills were not as well-developed, such as using complex sentences, reading, or speaking at a typical rate. As expected, significant differences were found between males and females. The findings highlight major skill attainments, identify skills that should be the target of specific intervention programs, suggest variable trajectories to be tested more precisely through direct assessments and longitudinally, and provide baseline data for treatment studies.

Advances in the treatment of fragile X syndrome

The FMR1 mutations can cause a variety of disabilities, including cognitive deficits, attention-deficit/hyperactivity disorder, autism, and other socioemotional problems, in individuals with the full mutation form (fragile X syndrome) and distinct difficulties, including primary ovarian insufficiency, neuropathy and the fragile X-associated tremor/ataxia syndrome, in some older premutation carriers. Therefore, multigenerational family involvement is commonly encountered when a proband is identified with a FMR1 mutation. Studies of metabotropic glutamate receptor 5 pathway antagonists in animal models of fragile X syndrome have demonstrated benefits in reducing seizures, improving behavior, and enhancing cognition. Trials of metabotropic glutamate receptor 5 antagonists are beginning with individuals with fragile X syndrome. Targeted treatments, medical and behavioral interventions, genetic counseling, and family supports are reviewed here.

Fragile X syndrome: Neural network models of sequencing and memory

A comparative framework of memory processes in males with fragile X syndrome (FXS) and Typically Developing (TYP) mental age-match children is presented. Results indicate a divergence in sequencing skills, such that males with FXS recall sequences similarly to TYP children around five and a half years of age, but eth males with FXS recall significantly worse when compared to TYP children around seven and a half years of age. Performance on one working memory measure, an n-back card task, is modeled with a neural network. To date, no network models explicate the sequencing and memory processes in those with FXS. Noise was added to various levels (weight matrices) in the FXS model and outputs approximated human FXS performance. Three models were compared: 1) FXS; 2) younger mental age-TYP matches; and 3) older reading level-TYP matches. Modeling can help to reify conceptualizations of deficits and to guide in the creation of more valid, science-based remediations. The FXS model suggests that the levels of phonological representation and sequencing in memory are candidates for targeted therapies in males with FXS.

A mouse model of fragile X syndrome exhibits heightened arousal and/or emotion following errors or reversal of contingencies

This study was designed to further assess cognitive and affective functioning in a mouse model of Fragile X syndrome (FXS), the Fmr1(tm1Cgr) or Fmr1 "knockout" (KO) mouse. Male KO mice and wild-type littermate controls were tested on learning set and reversal learning tasks. The KO mice were not impaired in associative learning, transfer of learning, or reversal learning, based on measures of learning rate. Analyses of videotapes of the reversal learning task revealed that both groups of mice exhibited higher levels of activity and wall-climbing during the initial sessions of the task than during the final sessions, a pattern also seen for trials following an error relative to those following a correct response. Notably, the increase in both behavioral measures seen early in the task was significantly more pronounced for the KO mice than for controls, as was the error-induced increase in activity level. This pattern of effects suggests that the KO mice reacted more strongly than controls to the reversal of contingencies and pronounced drop in reinforcement rate, and to errors in general. This pattern of effects is consistent with the heightened emotional reactivity frequently described for humans with FXS.

Open-label treatment trial of lithium to target the underlying defect in fragile X syndrome

OBJECTIVE

In fragile X syndrome (FXS), it is hypothesized that absence of the fragile X mental retardation protein (FMRP) disrupts regulation of group 1 metabotropic glutamate receptor (mGluR and mGluR5)-dependent translation in dendrites. Lithium reduces mGluR-activated translation and reverses phenotypes in the dfxr mutant fly and fmr1 knockout mouse. This pilot add-on trial was conducted to evaluate safety and efficacy of lithium in humans with FXS.

METHODS

Fifteen individuals with FXS, ages 6-23, received lithium titrated to levels of 0.8-1.2 mEq/L. The primary outcome measure, the Aberrant Behavior Checklist --Community Edition (ABC-C) Irritability Subscale, secondary outcome measures (other ABC-C subscales, clinical global improvement scale (CGI), visual analog scale for behavior (VAS), Vineland Adaptive Behavior Scale (VABS)), exploratory cognitive and psychophysiological measures and an extracellular signal-regulated kinase (ERK) activation assay were administered at baseline and 2 months of treatment. Side effects were quantified with a standardized checklist and lithium level, complete blood count (CBC), thyroid stimulating hormone (TSH), and chemistry screen were done at baseline, 2 weeks, 4 weeks and 2 months.

RESULTS

The only significant treatment-related side effects were polyuria/polydipsia (n = 7) and elevated TSH (n = 4). Although the ABC-C Irritability Subscale showed only a trend toward improvement, there was significant improvement in the Total ABC-C score (p = 0.005), VAS (p = 0.003), CGI (p = 0.002), VABS Maladaptive Behavior Subscale (p = 0.007), and RBANS List Learning (p = 0.03) and an enhanced ERK activation rate (p = 0.007). Several exploratory tasks proved too difficult for lower-functioning FXS subjects.

CONCLUSIONS

Results from this study are consistent with results in mouse and fly models of FXS, and suggest that lithium is well-tolerated and provides functional benefits in FXS, possibly by modifying the underlying neural defect. A placebo-controlled trial of lithium in FXS is warranted.

Working memory in individuals with fragile X syndrome

The present research tests the hypothesis that fragile X syndrome (FXS) is associated with a deficit in working memory (WM) and the deficit is more pronounced the higher the control requirements of the task. To this purpose, 15 boys with FXS and 15 typically developing children, matched for mental age, assessed with Logical Operation Test, were tested with batteries of 4 verbal and 4 visuospatial WM tasks requiring different levels of control. Children with FXS showed a performance equal to controls, in WM tasks requiring low and medium-low control but significant impairment in correspondence with greater control requirements. Results show that boys with FXS present a WM deficit only when high control is required by the task, supporting the hypothesis that control can be a critical variable distinguishing WM functions and explaining intellectual differences. On the contrary the hypothesis that the FXS is associated with a visuospatial deficit was not supported.

Age-dependent cognitive changes in carriers of the fragile X syndrome

Fragile X syndrome is a neurodevelopmental disorder that is caused by the silencing of a single gene on the X chromosome, the fragile X mental retardation 1 (FMR1) gene. Affected individuals display a unique neurocognitive phenotype that includes significant impairment in inhibitory control, selective attention, working memory, and visual-spatial cognition. In contrast, little is known about the trajectory and specificity of any cognitive impairment associated with the fragile X premutation (i.e., "carrier status") or its relationship with the recently identified neurodegenerative disorder, fragile X-associated tremor/ataxia syndrome (FXTAS). In the present study, we evaluated a broad sample of 40 premutation males (PM) aged 18-69 years matched on age and IQ to 67 unaffected comparison males (NC). Performance was compared across a range of cognitive domains known to be impaired in fragile X syndrome (i.e., "full mutation"). Tremor was also assessed using a self-report neurological questionnaire. PM displayed statistically significant deficits in their ability to inhibit prepotent responses, differentiating them from NC from age 30 onwards. With increasing age, the two groups follow different trajectories, with PM developing progressively more severe problems in inhibitory control. This deficit also has a strong co-occurrence in males displaying FXTAS-related symptomatology (p<.001). Selective attention was also impaired in PM but did not show any disproportionate aging effect. No other cognitive deficits were observed. We conclude that an inhibitory deficit and its impact across the lifespan are specifically associated with the fragile X premutation status, and may be a precursor for development of a more severe form of cognitive impairment or dementia, which has been reported in patients with the diagnosis of FXTAS.

The fragile X continuum: new advances and perspectives

Fragile X syndrome is the world's most common hereditary cause of intellectual disability in men and to a lesser extent in women. The disorder is caused by the silencing of a single gene on the X chromosome, the Fragile X Mental Retardation Gene-1. A substantial body of research across the disciplines of molecular genetics, child psychiatry and developmental neuroscience bears testament to a decade of exciting and innovative science that has advanced our knowledge about the fragile X 'signature' or influence across cognitive and social development. The core aims of this review are to first discuss fragile X syndrome and premutation involvement in the context of current advances that demonstrate the dynamic nature of the genotype on phenotypic outcomes. Second, to discuss the implications of these recent advances for the development of clinical and educational interventions and resource tools that target specific phenotypic 'signatures' within the fragile X continuum.

Developmental course of psychopathology in youths with and without intellectual disabilities

BACKGROUND

We aimed to describe similarities and differences in the developmental course of psychopathology between children with and without intellectual disabilities (ID).

METHODS

Multilevel growth curve analysis was used to analyse the developmental course of psychopathology, using the Child Behavior Checklist (CBCL), in two longitudinal multiple-birth-cohort samples of 6- to 18-year-old children with ID (N = 978) and without ID (N = 2,047) using three repeated measurements across a 6-year period.

RESULTS

Children with ID showed a higher level of problem behaviours across all ages compared to children without ID. A significant difference between the samples in the developmental courses was found for Aggressive Behaviour and Attention Problems, where children with ID showed a significantly larger decrease. Gender differences in the development of psychopathology were similar in both samples, except for Social Problems where males with ID showed a larger decrease in problem behaviour across time than females with ID and males and females without ID.

CONCLUSIONS

Results indicate that children with ID continue to show a greater risk for psychopathology compared to typically developing children, although this higher risk is less pronounced at age 18 than it is at age 6 for Aggressive Behaviour. Contrary to our expectations, the developmental course of psychopathology in children with ID was quite similar from age 6 to 18 compared to children without ID. The normative developmental trajectories of psychopathology in children with ID, presented here, can serve as a yardstick against which development of childhood psychopathology can be detected as deviant.

A multidisciplinary approach to the management of individuals with fragile X syndrome

BACKGROUND

Fragile X syndrome (FXS) is the most common inherited form of intellectual disability. Since the identification of the responsible gene (FMR1) and its protein (FMRP), there has been enormous progress in both clinical and pathogenetic research on the neurobehavioural aspects of the condition. However, studies regarding other medical problems anticipated in individuals with FXS are limited. A multidisciplinary study evaluating various causes of morbidity in the same group has not been published yet.

METHODS

Twenty-four boys with FXS full mutation were recruited out of a larger group of 103 diagnosed in one centre over the past 10 years. Ear nose and throat, eye and cardiac examinations were performed in addition to routine cognitive, behavioural, neurological and speech and language assessments.

RESULTS

The average IQ score was 49.8 +/- 20 (range 25-90). There were four patients (18%) with IQ above 70. Using DSM-IV, attention deficit hyperactivity disorder was diagnosed in five boys out of 22 examined (23%), while 32% were diagnosed with pervasive developmental disorder. The seizure frequency was 17%. A psychiatric disorder was diagnosed in six out of eight boys with electroencephalogram abnormalities (75%). Minimal conductive hearing loss was found in five (5/22) patients. There was significant delay in both expressive and receptive language skills. Ocular findings were refractive errors (13%) and strabismus (4.4%). Mitral valve prolapsus (MVP) was observed in 3/22 (13.7%) patients and aortic annulus dilatation was present in 2/22 (9%) patients.

CONCLUSIONS

Frequency of psychiatric diagnoses made with DSM-IV were in parallel to those reported in the literature. Comorbidity of seizures and psychiatric disorders was noteworthy. The percentage of 'high-functioning' full mutation males supports the previous observations. Ear nose and throat and eye examination revealed remarkably lower prevalence of abnormal findings than reported. MVP was slightly less frequent compared with the single study in the literature. Age at the time of examination had an effect on the outcome of cardiac evaluation. These findings will guide us in future management of the group of patients followed in our institution. The protocol applied provides an applicable outline for multidisciplinary institutional settings dealing with individuals with FXS.

Delineation of early attentional control difficulties in fragile X syndrome: focus on neurocomputational changes

Fragile X syndrome (FXS) is due to the silencing of a single X-linked gene and it is associated with striking attentional difficulties. As FXS is well characterised at the cellular level, the condition provides a unique opportunity to investigate how a genetic dysfunction can impact on the development of neurocomputational properties relevant to attention. Thirteen young boys with FXS and 13 mental-age-matched typically developing controls performed a touch-screen-based search task that manipulated the similarity between targets and distractors and their heterogeneity in size. Search speed, path and errors were recorded as multiple measures of performance. Children did not differ in overall search speed or path when searching amongst distractors, but striking error patterns distinguished children with FXS from controls. Firstly, although clear markers of previously found targets remained on screen, children with FXS perseverated on touching previous hits more than typically developing controls, consistent with the well-documented inhibitory deficits in adults with the disorder. Secondly, they could accurately discriminate single target-distractor pairs, but, when searching a complex display, they touched distractors more often than control children when distractors were similar to targets and especially so when these were infrequent, highlighting difficulties in judging relative size and allocate attentional weight independently of stimulus frequency. Thirdly, their performance was also characterised by inaccuracies in pointing, suggesting additional motor control deficits. Taken together, the findings suggest that fragile X syndrome affects the early development of multiple processes contributing to efficient attentional selection, as would be predicted from an understanding of the neurocomputational changes associated with the disorder.

Autism spectrum disorder in Fragile X syndrome: differential contribution of adaptive socialization and social withdrawal

The present study extends our previous work on characterizing the profile of social behavior abnormalities in boys with Fragile X (FraX) and autism spectrum disorder (ASD) using clinically oriented behavioral rating scales and standardized instruments. The goal was to further distinguish behavioral parameters contributing to the diagnostic classification of FraX + ASD. The study design included two cohorts of boys with FraX (3-8 years), a larger main cohort for cross-sectional analyses (n = 56, 24 with ASD), and a longitudinal subset (n = 30, 11 with ASD) of the main cohort with up to 3 yearly observations. The focus was on the relative contribution of delayed adaptive socialization and social withdrawal, including item components of their corresponding rating instruments, to the diagnosis of ASD in boys with FraX. Using a combination of regression analyses, we demonstrated that: (1) as delayed socialization, social withdrawal is also a correlate of FraX + ASD; (2) items of social withdrawal scales representing avoidance were the main predictors of ASD status, particularly in older boys; (3) adaptive socialization skills reflecting rules of social behavior and recognition and labeling of emotions, linked to verbal reasoning abilities, were selectively associated with FraX + ASD; (4) adaptive socialization is the primary determinant over time of ASD status in boys with FraX; and (5) integrated adaptive socialization-social withdrawal models allow the identification of distinctive FraX + ASD subgroups. Altogether, our findings suggest that two distinct but interrelated social behavior abnormalities, one linked to impaired cognitive processes (delayed socialization) and the second one to disturbance in limbic circuits (avoidance), play a role in the development of ASD in boys with FraX.