Michele D. Poe

Early Brain Overgrowth in Autism Associated With an Increase in Cortical Surface Area Before Age 2 Years

CONTEXT Brain enlargement has been observed in 2-year-old children with autism, but the underlying mechanisms are unknown. OBJECTIVE To investigate early growth trajectories in brain volume and cortical thickness. DESIGN Longitudinal magnetic resonance imaging study. SETTING Academic medical centers. PARTICIPANTS Fifty-nine children with autism spectrum disorder (ASD) and 38 control children. INTERVENTION Children were examined at approximately 2 years of age. Magnetic resonance imaging was repeated approximately 24 months later (when aged 4-5 years; 38 children with ASD; 21 controls). MAIN OUTCOME MEASURES Cerebral gray and white matter volumes and cortical thickness. RESULTS We observed generalized cerebral cortical enlargement in individuals with ASD at both 2 and 4 to 5 years of age. Rate of cerebral cortical growth across multiple brain regions and tissue compartments in children with ASD was parallel to that seen in the controls, indicating that there was no increase in rate of cerebral cortical growth during this interval. No cerebellar differences were observed in children with ASD. After controlling for total brain volume, a disproportionate enlargement in temporal lobe white matter was observed in the ASD group. We found no significant differences in cortical thickness but observed an increase in an estimate of surface area in the ASD group compared with controls for all cortical regions measured (temporal, frontal, and parieto-occipital lobes). CONCLUSIONS Our longitudinal magnetic resonance imaging study found generalized cerebral cortical enlargement in children with ASD, with a disproportionate enlargement in temporal lobe white matter. There was no significant difference from controls in the rate of brain growth for this age interval, indicating that brain enlargement in ASD results from an increased rate of brain growth before age 2 years. The presence of increased cortical volume, but not cortical thickness, suggests that early brain enlargement may be associated with increased cortical surface area. Cortical surface area overgrowth in ASD may underlie brain enlargement and implicates a distinct set of pathogenic mechanisms.

Neuropsychological profile of autism and the broad autism phenotype

CONTEXT Multiple articles describe a constellation of language, personality, and social-behavioral features present in relatives that mirror the symptom domains of autism, but are much milder in expression. Studies of this broad autism phenotype (BAP) may provide a potentially important complementary approach for detecting the genes causing autism and defining associated neural circuitry by identifying more refined phenotypes that can be measured quantitatively in both affected and unaffected individuals and that are tied to functioning in particular regions of the brain. OBJECTIVE To gain insight into neuropsychological features that index genetic liability to autism. DESIGN Case-control study. SETTING The general community. PARTICIPANTS Thirty-eight high-functioning individuals with autism and parents of autistic individuals, both with and without the BAP (n = 83), as well as control individuals. MAIN OUTCOME MEASURES A comprehensive battery of neuropsychological tasks assessing social cognition, executive function, and global vs local processing strategies (central coherence). RESULTS Both individuals with autism and parents with the BAP differed from controls on measures of social cognition, with performance in the other 2 domains being more similar to controls. CONCLUSIONS Data suggest that the social cognitive domain may be an important target for linking phenotype to cognitive process to brain structure in autism and may ultimately provide insight into the genes involved in autism.

Longitudinal study of amygdala volume and joint attention in 2- to 4-year-old children with autism

CONTEXT Cerebral cortical volume enlargement has been reported in 2- to 4-year-olds with autism. Little is known about the volume of subregions during this period of development. The amygdala is hypothesized to be abnormal in volume and related to core clinical features in autism. OBJECTIVES To examine amygdala volume at 2 years with follow-up at 4 years of age in children with autism and to explore the relationship between amygdala volume and selected behavioral features of autism. DESIGN Longitudinal magnetic resonance imaging study. SETTING University medical setting. PARTICIPANTS Fifty autistic and 33 control (11 developmentally delayed, 22 typically developing) children between 18 and 35 months (2 years) of age followed up at 42 to 59 months (4 years) of age. MAIN OUTCOME MEASURES Amygdala volumes in relation to joint attention ability measured with a new observational coding system, the Social Orienting Continuum and Response Scale; group comparisons including total tissue volume, sex, IQ, and age as covariates. RESULTS Amygdala enlargement was observed in subjects with autism at both 2 and 4 years of age. Significant change over time in volume was observed, although the rate of change did not differ between groups. Amygdala volume was associated with joint attention ability at age 4 years in subjects with autism. CONCLUSIONS The amygdala is enlarged in autism relative to controls by age 2 years but shows no relative increase in magnitude between 2 and 4 years of age. A significant association between amygdala volume and joint attention suggests that alterations to this structure may be linked to a core deficit of autism.

Cortical gray and white brain tissue volume in adolescents and adults with autism.

BACKGROUND A number of studies have found brain enlargement in autism, but there is disagreement as to whether this enlargement is limited to early development or continues into adulthood. In this study, cortical gray and white tissue volumes were examined in a sample of adolescents and adults with autism who had demonstrated total brain enlargement in a previous magnetic resonance imaging (MRI) study. METHODS An automated tissue segmentation program was applied to structural MRI scans to obtain volumes of gray, white, and cerebrospinal fluid (CSF) tissue on a sample of adolescent and adult males ages 13-29 with autism (n = 23) and controls (n = 15). Regional differences for brain lobes and brain hemispheres were also examined. RESULTS Significant enlargement in gray matter volume was found for the individuals with autism, with a disproportionate increase in left-sided gray matter volume. Lobe volume enlargements were detected for frontal and temporal, but not parietal or occipital lobes, in the subjects with autism. Age and nonverbal IQ effects on tissue volume were also observed. CONCLUSIONS These findings give evidence for left-lateralized gray tissue enlargement in adolescents and adults with autism, and demonstrate a regional pattern of cortical lobe volumes underlying this effect.

Hyperresponsive sensory patterns in young children with autism, developmental delay, and typical development.

The nature of hyperresponsiveness to sensory stimuli in children with autism, using a new observational measure, the SPA, was examined. Three groups of young participants were assessed (autism, developmental delay, typical). Across all groups, MA was a predictor of hyperresponsiveness, such that aversion to multisensory toys decreased as MA increased. The two clinical groups displayed higher levels of sensory aversion than the typical group. The groups did not differ in the proportion of children habituating to an auditory stimulus; however, nonresponders were more prevalent in the autism group. These findings elucidate developmental influences on sensory features and the specificity of hyperresponsiveness to clinical groups. Implications for understanding pathogenesis, differentiating constructs of hypersensitivity, and planning treatment are discussed.

Sensory features and repetitive behaviors in children with autism and developmental delays.

This study combined parent and observational measures to examine the association between aberrant sensory features and restricted, repetitive behaviors in children with autism (N=67) and those with developmental delays (N=42). Confirmatory factor analysis was used to empirically validate three sensory constructs of interest: hyperresponsiveness, hyporesponsiveness, and sensory seeking. Examining the association between the three derived sensory factor scores and scores on the Repetitive Behavior Scales—Revised revealed the co‐occurrence of these behaviors in both clinical groups. Specifically, high levels of hyperresponsive behaviors predicted high levels of repetitive behaviors, and the relationship between these variables remained the same controlling for mental age. We primarily found non‐significant associations between hyporesponsiveness or sensory seeking and repetitive behaviors, with the exception that sensory seeking was associated with ritualistic/sameness behaviors. These findings suggest that shared neurobiological mechanisms may underlie hyperresponsive sensory symptoms and repetitive behaviors and have implications for diagnostic classification as well as intervention.

Development of a Mouse Test for Repetitive, Restricted Behaviors: Relevance to Autism

Repetitive behavior, a core symptom of autism, encompasses stereotyped responses, restricted interests, and resistance to change. These studies investigated whether different components of the repetitive behavior domain could be modeled in the exploratory hole-board task in mice. Four inbred mouse strains, C57BL/6J, BALB/cByJ, BTBR T+tf/J, and FVB/NJ, and mice with reduced expression of Grin1, leading to NMDA receptor hypofunction (NR1neo/neo mice), were tested for exploration and preference for olfactory stimuli in an activity chamber with a 16-hole floor-board. Reduced exploration and high preference for holes located in the corners of the chamber were observed in BALB/cByJ and BTBR T+tf/J mice. All inbred strains had initial high preference for a familiar olfactory stimulus (clean cage bedding). BTBR T+tf/J was the only strain that did not demonstrate a shift in hole preference towards an appetitive olfactory stimulus (cereal or a chocolate chip), following home cage exposure to the food. The NR1neo/neo mice showed lower hole selectivity and aberrant olfactory stimulus preference, in comparison to wildtype controls. The results indicate that NR1neo/neo mice have repetitive nose poke responses that are less modified by environmental contingencies than responses in wildtype mice. 25-30% of NMDA receptor hypomorphic mice also show self-injurious responses. Findings from the olfactory studies suggest that resistance to change and restricted interests might be modeled in mice by a failure to alter patterns of hole preference following familiarization with an appetitive stimulus, and by high preference persistently demonstrated for one particular olfactory stimulus. Further work is required to determine the characteristics of optimal mouse social stimuli in the olfactory hole-board test.

Hyporesponsiveness to Social and Nonsocial Sensory Stimuli in Children with Autism, Children with Developmental Delays, and Typically Developing Children

This cross-sectional study seeks to (a) describe developmental correlates of sensory hyporesponsiveness to social and nonsocial stimuli, (b) determine whether hyporesponsiveness is generalized across contexts in children with autism relative to controls, and (c) test the associations between hyporesponsiveness and social communication outcomes. Three groups of children ages 11-105 months (N = 178; autism = 63, developmental delay = 47, typical development = 68) are given developmental and sensory measures including a behavioral orienting task (the Sensory Processing Assessment). Lab measures are significantly correlated with parental reports of sensory hyporesponsiveness. Censored regression models show that hyporesponsiveness decreased across groups with increasing mental age (MA). Group differences are significant but depend upon two-way interactions with MA and context (social and nonsocial). At a very young MA (e.g., 6 months), the autism group demonstrates more hyporesponsiveness to social and nonsocial stimuli (with larger effects for social) than developmental delay and typically developing groups, but at an older MA (e.g., 60 months) there are no significant differences. Hyporesponsiveness to social and nonsocial stimuli predicts lower levels of joint attention and language in children with autism. Generalized processes in attention disengagement and behavioral orienting may have relevance for identifying early risk factors of autism and for facilitating learning across contexts to support the development of joint attention and language.

A Staging System for Infantile Krabbe Disease to Predict Outcome After Unrelated Umbilical Cord Blood Transplantation

OBJECTIVE. Infantile Krabbe disease, a rare neurodegenerative disorder that leads to rapid demyelination, dysmyelination, and death in the first 2 years of life, is responsive to treatment with umbilical cord blood transplantation provided that the patient is treated in the first weeks of life. At present, family history is the only way to identify patients that are asymptomatic with most patients being diagnosed after onset of symptoms. We hypothesized that a staging system based on clinical indicators and neurophysiological and neuroimaging measures can predict posttreatment variation in patients diagnosed with infantile Krabbe disease. METHODS. A retrospective review of pretransplant clinical indicators and neurodevelopmental, brain imaging and neurophysiological measures was performed in 42 patients being considered for treatment with umbilical cord blood transplantation. Based on these evaluations, an expert system approach was used to develop a staging system for infantile Krabbe disease. Another set of analyses in the subset of patients who were transplanted (n = 29) evaluated the association between pretransplant stage of disease and posttransplant neurodevelopmental outcomes. RESULTS. A staging algorithm for infants with infantile Krabbe disease was developed and tested for predicting neurodevelopmental outcome after umbilical cord blood transplantation. Standard neurophysiological and neuroimaging tests were not useful in the staging algorithm. Clinical indicators were found to best classify stage of disease. Pretransplant stage was found to be predictive of neurodevelopmental outcome. CONCLUSIONS. We conclude that the clinical staging system based solely on signs and symptoms of disease can be used to predict outcomes after umbilical cord blood transplantation. This staging system can be used prospectively to guide physicians unfamiliar with the disorder in evaluating, monitoring, and counseling families about treatment outcomes. The staging will be useful for both patients diagnosed with infantile Krabbe disease because of clinical symptoms and those identified through neonatal screening programs.

Trajectories of Early Brain Volume Development in Fragile X Syndrome and Autism.

OBJECTIVE To examine patterns of early brain growth in young children with fragile X syndrome (FXS) compared with a comparison group (controls) and a group with idiopathic autism. METHOD The study included 53 boys 18 to 42 months of age with FXS, 68 boys with idiopathic autism (autism spectrum disorder), and a comparison group of 50 typically developing and developmentally delayed controls. Structural brain volumes were examined using magnetic resonance imaging across two time points, at 2 to 3 and again at 4 to 5 years of age, and total brain volumes and regional (lobar) tissue volumes were examined. In addition, a selected group of subcortical structures implicated in the behavioral features of FXS (e.g., basal ganglia, hippocampus, amygdala) was studied. RESULTS Children with FXS had larger global brain volumes compared with controls but were not different than children with idiopathic autism, and the rate of brain growth from 2 to 5 years of age paralleled that seen in controls. In contrast to children with idiopathic autism who had generalized cortical lobe enlargement, children with FXS showed specific enlargement in the temporal lobe white matter, cerebellar gray matter, and caudate nucleus, but a significantly smaller amygdala. CONCLUSIONS This structural longitudinal magnetic resonance imaging study of preschoolers with FXS observed generalized brain overgrowth in children with FXS compared with controls, evident at age 2 and maintained across ages 4 to 5. In addition, different patterns of brain growth that distinguished boys with FXS from boys with idiopathic autism were found.