Exuberant social and linguistic development characterize the first years of life for the typical child, whereas deviant, stymied, or regressive development mark these years for the child with autism. The brain bases underlying the emergence of complex cognitive capacities in typical and atypical development remain speculative due to the current difficulty in acquiring functional brain imaging data from infants and toddlers without motion artifact. Through the use of a novel technique in which functional magnetic resonance imaging (fMRI) data are collected during natural sleep, this dissertation provides the first fMRI studies of functional brain organization in 1-4 year old typically-developing children and 2-3 year- old children with autism. The feasibility of the sleep fMRI technique was investigated through two studies of typically-developing children. First, presentation of auditory and visual stimuli to typical 2-4 year-old children during sleep revealed differential activity between and within stimulus modalities. Furthermore, stimulus-independent auditory and visual networks were identified. Second, presentation of speech and nonspeech stimuli to two groups of typical children (toddlers and 3 year-olds) revealed age-related differences in the brain response to speech. Specifically, toddlers recruited an extended network pattern of brain activity encompassing frontal, occipital, and cerebellar regions. The 3 year- olds, however, showed a more focal pattern of BOLD activity primarily within bilateral superior temporal regions. This time-delimited, extended pattern of brain activity in the typical toddlers may allow for the rapid burst in language growth seen during the second year of life. These studies add to the growing body of literature indicating that stimulus discrimination and intrinsic functional networks persist during sleep. When speech and nonspeech stimuli were presented to 2-3 year old children with autism spectrum disorder (ASD), a pattern of brain activity was identified that differed from two typically- developing control groups. In comparison to their mental age-matched controls (MA), the ASD group recruited a reduced number of brain regions within the 'extended network'. In comparison to their chronological age-matched controls (CA), the ASD group showed a greater reliance on right hemisphere brain regions. The discussion suggests possible implications of an early, right hemisphere, deviant developmental trajectory for the etiology of autism

BACKGROUND: Anxiety is one of the most common co-occurring conditions in people with autism spectrum disorder. The amygdala has been identified as being associated with anxiety in populations with and without autism, yet associations in autism were based on relatively small or developmentally constrained samples, leaving questions as to whether these results hold at different developmental ages and in a larger, more robust sample. METHODS: Structural neuroimaging and parent report of anxiety symptoms of children ages 5-13 years with (n = 123) and without (n = 171) a diagnosis of autism were collected from the University of Maryland and three sites from the Autism Brain Imaging Data Exchange. Standardized residuals for bilateral amygdala volumes were computed adjusting for site, hemispheric volumes, and covariates (age, sex, Full Scale IQ). RESULTS: Clinically significant anxiety symptoms did not differentiate amygdala volumes between groups (i.e., autism and anxiety, autism without anxiety, without autism or anxiety). No significant association between left or right amygdala volumes and anxiety scores was observed among the sample of individuals with autism. Meta-analytic and Bayes factor estimations provided additional support for the null hypothesis. Age, sex, and autism severity did not moderate associations between anxiety and amygdala volumes. CONCLUSIONS: No relation between amygdala volumes and anxiety symptoms in children with autism was observed in the largest sample to investigate this question. We discuss directions for future research to determine whether additional factors including age or method of assessment may contribute to this lack of association.

Although many studies have examined the location and function of the mirror neuron system (MNS) in human adults, we know relatively little about its development. The current study fills this gap by using fMRI to examine for the first time the development of the brain regions implicated in action execution, action observation, and their overlap. We examined age-related differences in brain activation by contrasting a group of children (n = 21) and adults (n = 18). Surfaced-based analyses of action execution and action observation revealed that brain activity for action observation and execution in children is similar to adults, though adults displayed greater activity than children within the right superior parietal lobe during action execution and the occipital lobe during action observation compared to control. Further, within-individual measures of overlapping activation between action observation and execution revealed age-related differences, such that adults, compared to children, displayed more spatial overlap. Moreover, the extent of the overlap in activation across conditions was related to better motor skills and action representation abilities in children. These data indicate that the MNS changes between middle childhood and adulthood. The data also demonstrate the functional significance of the putative MNS to motor skills and action representation during development.

This study aimed to examine changes in depression and anxiety symptoms from before to during the first 6 months of the COVID-19 pandemic in a sample of 1,339 adolescents (9-18 years old, 59% female) from three countries. We also examined if age, race/ethnicity, disease burden, or strictness of government restrictions moderated change in symptoms. Data from 12 longitudinal studies (10 U.S., 1 Netherlands, 1 Peru) were combined. Linear mixed effect models showed that depression, but not anxiety, symptoms increased significantly (median increase = 28%). The most negative mental health impacts were reported by multiracial adolescents and those under 'lockdown' restrictions. Policy makers need to consider these impacts by investing in ways to support adolescents' mental health during the pandemic.