Peabody Picture Vocabulary Test: Proxy for Verbal IQ in Genetic Studies of Autism Spectrum Disorder.

This study assessed the utility of a brief assessment (the Peabody Picture Vocabulary Test-4th Edition; PPVT4) as a proxy for verbal IQ (VIQ) in large-scale studies of autism spectrum disorder (ASD). In a sample of 2,420 proband with ASD, PPVT4:IQ correlations were strong. PPVT4 scores were, on average, 5.46 points higher than VIQ; 79% of children had PPVT4 scores within one standard deviation (+/-15) of their VIQ and 90% were similarly classified as having abilities above or below 70 on both measures. Distributions of PPVT4 and VIQ by de novo mutation status were highly similar. These results strongly support the utility of PPVT4 as a proxy for VIQ in large-scale ASD studies, particularly for genetic investigations.

Understanding definitions of minimally verbal across instruments: evidence for subgroups within minimally verbal children and adolescents with autism spectrum disorder.

BACKGROUND: Minimally verbal (MV) children with autism spectrum disorder (ASD) are often assumed to be profoundly cognitively impaired and excluded from analyses due to challenges completing standardized testing protocols. A literature aimed at increasing understanding of this subgroup is emerging; however, the many methods used to define MV status make it difficult to compare studies. Understanding how different instruments and definitions used to identify MV children affect sample composition is critical to advance research on this understudied clinical population. METHOD: The MV status of 1,470 school-aged children was defined using five instruments commonly used in ASD research. MV sample composition was compared across instruments. Analyses examined the proportion of overlap across MV subgroups and the extent to which child characteristics varied across MV subgroups defined using different definitions or combinations of measures. RESULTS: A total of 257 children were classified as MV on at least one instrument. Proportion of overlap between definitions ranged from 3% to 100%. The stringency of definition (i.e. few-to-no vs. some words) was associated with differences in cognitive and adaptive functioning; more stringent definitions yielded greater consistency of MV status across instruments. Cognitive abilities ranged from profoundly impaired to average intelligence; 16% had NVIQ ≥ 70. Approximately half exhibited verbal skills commensurate with nonverbal cognitive ability, whereas half had verbal abilities significantly lower than their estimated NVIQ. CONCLUSIONS: Future studies of MV children must carefully consider the methods used to identify their sample, acknowledging that definitions including children with 'some words' may yield larger samples with a wider range of language and cognitive abilities. Broadly defined MV samples may be particularly important to delineate factors interfering with language development in the subgroup of children whose expressive impairments are considerably below their estimated nonverbal cognitive abilities.

Developmental trajectories of cerebral blood flow and oxidative metabolism at baseline and during working memory tasks.

The neurobiological interpretation of developmental BOLD fMRI findings remains difficult due to the confounding issues of potentially varied baseline of brain function and varied strength of neurovascular coupling across age groups. The central theme of the present research is to study the development of brain function and neuronal activity through in vivo assessments of cerebral blood flow (CBF), oxygen extraction fraction (OEF) and cerebral metabolic rate of oxygen (CMRO2) both at baseline and during the performance of a working memory task in a cohort of typically developing children aged 7 to 18years. Using a suite of 4 emerging MRI technologies including MR blood oximetry, phase-contrast MRI, pseudo-continuous arterial spin labeling (pCASL) perfusion MRI and concurrent CBF/BOLD fMRI, we found: 1) At baseline, both global CBF and CMRO2 showed an age related decline while global OEF was stable across the age group; 2) During the working memory task, neither BOLD nor CBF responses showed significant variations with age in the activated fronto-parietal brain regions. Nevertheless, detailed voxel-wise analyses revealed sub-regions within the activated fronto-parietal regions that show significant decline of fractional CMRO2 responses with age. These findings suggest that the brain may become more "energy efficient" with age during development.

Assessing intracranial vascular compliance using dynamic arterial spin labeling.

Vascular compliance (VC) is an important marker for a number of cardiovascular diseases and dementia, which is typically assessed in the central and peripheral arteries indirectly by quantifying pulse wave velocity (PWV), and/or pulse pressure waveform. To date, very few methods are available for the quantification of intracranial VC. In the present study, a novel MRI technique for in-vivo assessment of intracranial VC was introduced, where dynamic arterial spin labeling (ASL) scans were synchronized with the systolic and diastolic phases of the cardiac cycle. VC is defined as the ratio of change in arterial cerebral blood volume (ΔCBV) and change in arterial pressure (ΔBP). Intracranial VC was assessed in different vascular components using the proposed dynamic ASL method. Our results show that VC mainly occurs in large arteries, and gradually decreases in small arteries and arterioles. The comparison of intracranial VC between young and elderly subjects shows that aging is accompanied by a reduction of intracranial VC, in good agreement with the literature. Furthermore, a positive association between intracranial VC and cerebral perfusion measured using pseudo-continuous ASL with 3D GRASE MRI was observed independent of aging effects, suggesting loss of VC is associated with a decline in perfusion. Finally, a significant positive correlation between intracranial and central (aortic arch) VC was observed using an ungated phase-contrast 1D projection PWV technique. The proposed dynamic ASL method offers a promising approach for assessing intracranial VC in a range of cardiovascular diseases and dementia.

Towards the identification of multi-parametric quantitative MRI biomarkers in lupus nephritis.

PURPOSE: To identify potential biomarkers of the renal impairment in lupus nephritis using a multi-parametric renal quantitative MRI (qMRI) protocol including diffusion weighted imaging (DWI), blood oxygen level dependent (BOLD), arterial spin labeling (ASL) and T1rho MRI between a cohort of healthy volunteers and lupus nephritis (LN) patients. MATERIALS AND METHODS: The renal qMRI protocol was performed twice with repositioning in between on 10 LN patients and 10 matched controls at 1.5 T. Navigator-gated and breath-hold acquisitions followed by non-rigid image registration were used to control respiratory motion. The repeatability of the 4 MRI modalities was evaluated with the intra-class correlation coefficient (ICC) and within-subject coefficient of variation (wsCV). Unpaired t-test and stepwise logistic regression were carried out to evaluate qMRI parameters between the LN and control groups. RESULTS: The reproducibility of the 4 qMRI modalities ranged from moderate to good (ICC=0.4-0.91, wsCV≤12%) with a few exceptions. T1rho MRI and ASL renal blood flow (RBF) demonstrated significant differences between the LN and control groups. Stepwise logistic regression yielded only one significant parameter (medullar T1rho) in differentiating LN from control groups with 95% accuracy. CONCLUSION: A reasonable degree of test-retest repeatability and accuracy of a multi-parametric renal qMRI protocol has been demonstrated in healthy volunteers and LN subjects. T1rho and ASL RBF are promising imaging biomarkers of LN.

Neurobiology of Sensory Overresponsivity in Youth With Autism Spectrum Disorders.

IMPORTANCE: More than half of youth with autism spectrum disorders (ASDs) have sensory overresponsivity (SOR), an extreme negative reaction to sensory stimuli. However, little is known about the neurobiological basis of SOR, and there are few effective treatments. Understanding whether SOR is due to an initial heightened sensory response or to deficits in regulating emotional reactions to stimuli has important implications for intervention. OBJECTIVE: To determine differences in brain responses, habituation, and connectivity during exposure to mildly aversive sensory stimuli in youth with ASDs and SOR compared with youth with ASDs without SOR and compared with typically developing control subjects. DESIGN, SETTING, AND PARTICIPANTS: Functional magnetic resonance imaging was used to examine brain responses and habituation to mildly aversive auditory and tactile stimuli in 19 high-functioning youths with ASDs and 19 age- and IQ-matched, typically developing youths (age range, 9-17 years). Brain activity was related to parents' ratings of children's SOR symptoms. Functional connectivity between the amygdala and orbitofrontal cortex was compared between ASDs subgroups with and without SOR and typically developing controls without SOR. The study dates were March 2012 through February 2014. MAIN OUTCOMES AND MEASURES: Relative increases in blood oxygen level-dependent signal response across the whole brain and within the amygdala during exposure to sensory stimuli compared with fixation, as well as correlation between blood oxygen level-dependent signal change in the amygdala and orbitofrontal cortex. RESULTS: The mean age in both groups was 14 years and the majority in both groups (16 of 19 each) were male. Compared with neurotypical control participants, participants with ASDs displayed stronger activation in primary sensory cortices and the amygdala (P < .05, corrected). This activity was positively correlated with SOR symptoms after controlling for anxiety. The ASDs with SOR subgroup had decreased neural habituation to stimuli in sensory cortices and the amygdala compared with groups without SOR. Youth with ASDs without SOR showed a pattern of amygdala downregulation, with negative connectivity between the amygdala and orbitofrontal cortex (thresholded at z > 1.70, P < .05). CONCLUSIONS AND RELEVANCE: Results demonstrate that youth with ASDs and SOR show sensorilimbic hyperresponsivity to mildly aversive tactile and auditory stimuli, particularly to multiple modalities presented simultaneously, and show that this hyperresponsivity is due to failure to habituate. In addition, findings suggest that a subset of youth with ASDs can regulate their responses through prefrontal downregulation of amygdala activity. Implications for intervention include minimizing exposure to multiple sensory modalities and building coping strategies for regulating emotional response to stimuli.

The pediatric template of brain perfusion.

Magnetic resonance imaging (MRI) captures the dynamics of brain development with multiple modalities that quantify both structure and function. These measurements may yield valuable insights into the neural patterns that mark healthy maturation or that identify early risk for psychiatric disorder. The Pediatric Template of Brain Perfusion (PTBP) is a free and public neuroimaging resource that will help accelerate the understanding of childhood brain development as seen through the lens of multiple modality neuroimaging and in relation to cognitive and environmental factors. The PTBP uses cross-sectional and longitudinal MRI to quantify cortex, white matter, resting state functional connectivity and brain perfusion, as measured by Arterial Spin Labeling (ASL), in 120 children 7-18 years of age. We describe the PTBP and show, as a demonstration of validity, that global summary measurements capture the trajectories that demarcate critical turning points in brain maturation. This novel resource will allow a more detailed understanding of the network-level, structural and functional landmarks that are obtained during normal adolescent brain development.

Simultaneous multi-slice Turbo-FLASH imaging with CAIPIRINHA for whole brain distortion-free pseudo-continuous arterial spin labeling at 3 and 7 T.

Simultaneous multi-slice (SMS) or multiband (MB) imaging has recently been attempted for arterial spin labeled (ASL) perfusion MRI in conjunction with echo-planar imaging (EPI) readout. It was found that SMS-EPI can reduce the T1 relaxation effect of the label and improve image coverage and resolution with little penalty in signal-to-noise ratio (SNR). However, EPI still suffers from geometric distortion and signal dropout from field inhomogeneity effects especially at high and ultrahigh magnetic fields. Here we present a novel scheme for achieving high fidelity distortion-free quantitative perfusion imaging by combining pseudo-continuous ASL (pCASL) with SMS Turbo-FLASH (TFL) readout at both 3 and 7 T. Bloch equation simulation was performed to characterize and optimize the TFL-based pCASL perfusion signal. Two MB factors (3 and 5) were implemented in SMS-TFL pCASL and compared with standard 2D TFL and EPI pCASL sequences. The temporal SNR of SMS-TFL pCASL relative to that of standard TFL pCASL was 0.76 ± 0.10 and 0.74 ± 0.11 at 7 T and 0.70 ± 0.05 and 0.65 ± 0.05 at 3T for MB factor of 3 and 5, respectively. By implementing background suppression in conjunction with SMS-TFL at 3T, the relative temporal SNR improved to 0.84 ± 0.09 and 0.79 ± 0.10 for MB factor of 3 and 5, respectively. Compared to EPI pCASL, significantly increased temporal SNR (p<0.001) and improved visualization of orbitofrontal cortex were achieved using SMS-TFL pCASL. By combining SMS acceleration with TFL pCASL, we demonstrated the feasibility for whole brain distortion-free quantitative mapping of cerebral blood flow at high and ultrahigh magnetic fields.

Reciprocal social behavior in youths with psychotic illness and those at clinical high risk.

Youths at clinical high risk (CHR) for psychosis typically exhibit significant social dysfunction. However, the specific social behaviors associated with psychosis risk have not been well characterized. We administer the Social Responsiveness Scale (SRS), a measure of autistic traits that examines reciprocal social behavior, to the parents of 117 adolescents (61 CHR individuals, 20 age-matched adolescents with a psychotic disorder [AOP], and 36 healthy controls) participating in a longitudinal study of psychosis risk. AOP and CHR individuals have significantly elevated SRS scores relative to healthy controls, indicating more severe social deficits. Mean scores for AOP and CHR youths are typical of scores obtained in individuals with high functioning autism (Constantino & Gruber, 2005). SRS scores are significantly associated with concurrent real-world social functioning in both clinical groups. Finally, baseline SRS scores significantly predict social functioning at follow-up (an average of 7.2 months later) in CHR individuals, over and above baseline social functioning measures (p < .009). These findings provide novel information regarding impairments in domains critical for adolescent social development, because CHR individuals and those with overt psychosis show marked deficits in reciprocal social behavior. Further, the SRS predicts subsequent real-world social functioning in CHR youth, suggesting that this measure may be useful for identifying targets of treatment in psychosocial interventions.