This past year we have continued to evaluate the neural characteristics and associated behavioral consequences of Autism Spectrum Disorder (ASD) in high-functioning individuals (i.e., without intellectual disability). One goal that we have pursued is to gain a better understanding of the sensory processing difficulties experience by our ASD participants. Picky eating and other poor eating habits are common among adolescents with ASD and are often related to aberrant sensory experience, including heightened reactivity to food taste and texture. However, little is known about the neural mechanisms that underlie eating difficulties in ASD. To address this issue, we evaluated neural responses to gustatory stimuli (tastants and pictures of foods) using fMRI and the relation between these gustatory responses and self-reported eating habits (Avery et al., Neuroimage Clinical, 2018). We found that eating-related problems were associated with abnormally strong neural responses in gustatory cortex to pictures of foods, as well as with atypical functional connectivity of gustatory cortex with other regions of the brain. These brain-based differences may predispose these individuals to maladaptive and unhealthy patterns of selective eating behavior. In addition to our focus on sensory processes, such as taste, we have continued our investigations into higher-order aspects of cognition. Primary among these are difficulties with social communication - one of the major hallmarks of ASD. We have evaluated the neural underpinnings of this pervasive problem using behavioral evaluations coupled with measures of cortical thickness based on structural MRI brain scans (Crutcher et al., Autism Research, 2018). The major finding from this effort was a strong relationship between the ASD subjects' self-ratings of social communication difficulties and the thickness of their cerebral cortex. Specifically, poorer self-ratings of social communication were associated with thinner cortex in two brain regions linked to language skills and social processes, the left inferior frontal gyrus and the left medial prefrontal cortex. Thus, consistent with other findings, these data suggest that ASD individuals may have thinner cortices than typically developing (TD) participants in specific regions of the brain, and that this cortical thinning may be an indicator of selective cognitive difficulties. Individuals with ASD without intellectual disability often have normal structural language abilities but deficits in social aspects of communication like pragmatics, prosody, and other aspects of speech. Although spontaneous conversation is the most commonplace yet challenging social task that ASD subjects typically confront, there have been virtually no neuroimaging studies of neural activity during overt speech. This lack of study has been largely due to technical issues involving participant motion while speaking aloud in the scanner that can make analysis of the fMRI data extremely challenging. In a recent study we have been able to overcome this limitation, thereby allowing us to scan ASD and TD participants while they engaged in face-to-face verbal interactions with an experimenter (Jasmin et al., Brain, 2019). Our subjects completed two kinds of tasks: conversation, which had high social demand, and repetition, which had low social demand. Autistic individuals showed abnormally increased interregional correlation relative to control subjects during spontaneous conversation, especially among social processing brain regions. Furthermore, these increased correlations were associated with parent ratings of the ASD participants social impairments. These results add to a growing body of data on the aberrant patterns of neural connectivity in ASD and pave the way for more ecologically valid fMRI evaluations on other aspects of social processing in ASD and other neuropsychiatric disorders. We have also continued our efforts to determine differences and commonalities in the clinical profiles of adolescent girls and boys with ASD (Ratto et al., Journal of Autism & Developmental Disorders, 2018). Of particular interest, our large-scale study of age- and IQ-matched ASD adolescents (N = 228) revealed that, although females and males were rated similarly on gold-standard diagnostic measures overall (ADOS and ADI-R), females with higher IQs were less likely to meet criteria on the ADI-R. Females were also found to be significantly more impaired on parent reported autistic traits and adaptive skills. Overall, these findings suggest that some autistic females may be missed by current diagnostic procedures, thereby providing evidence for the need for clinical instruments specifically designed for the evaluating ASD in females. We have also begun to evaluate the possibility that ASD may have different neural consequences in girls than boys (Smith et al., Frontiers in Human Neuroscience, 2019). In a preliminary report on a relatively small number of females (N = 24) we found differences in the connectivity of the cerebellum to other brain regions in the girls relative to boys with ASD (N=120). These results shed some light on the possibility of sex-specific pathophysiology of ASD and are indicative of potentially divergent neurodevelopmental trajectories for each sex. This sex-dependent, aberrant cerebellar connectivity in ASD might also underlie some of the motor and/or socio-affective difficulties experienced by members of this population, although the symptomatic correlate(s) of these brain findings remain unknown.
Showing the most recent 10 out of 45 publications
