Diffusion Tensor Imaging in Autism Spectrum Disorder: A Review
Brittany G. Travers, Nagesh Adluru, Chad Ennis, Do P. M. Tromp, Dan Destiche, Sam Doran, Erin D. Bigler, Nicholas Lange, Janet E. Lainhart, and Andrew L. Alexander
White matter tracts are like the “highways” of the brain, allowing for fast and efficient communication among diverse brain regions. The purpose of this paper is to review the results of autism studies that have used diffusion tensor imaging, which is a neuroimaging method that allows us to examine the structure and integrity of these white matter tracts. From the 48 studies we reviewed, persons with autism spectrum disorder (ASD) tended to have decreased white matter integrity spanning across many regions of the brain but most consistently in regions such as the corpus callosum (connecting the left and right hemispheres and associated with motor skill and complex information processing), the cingulum bundles (connecting regions along the middle-line of the brain with important frontal projections and associated with executive function), and white matter tracts that pass through the temporal lobe (connecting temporal lobe regions with other brain regions and associated with language and social functioning). The pattern of results in these studies suggests that the white matter tracts may be atypical in persons with ASD. Additionally, the review suggests that people with ASD may not exhibit the typical left-greater-than-right-brain asymmetry in white matter integrity compared with people with typical development. White matter alterations in persons with ASD are a target of emerging interventions and may help identify the brain basis of individual differences in this population. © 2012 INSAR/Wiley Periodicals, Inc.
Article citation: Autism Res 2012, 5: 289–313. DOI: 10.1002/aur.1243
Atypical Visuospatial Processing in Autism: Insights from Functional Connectivity Analysis
Katherine Johnson, Christine Ecker, Erik O'Hanlon, Michael Gill, Louise Gallagher, and Hugh Garavan
Numerous studies have reported atypical processing of visual-spatial information in individuals with autism spectrum disorder (ASD), but the cause is unknown. There is extensive evidence to suggest neural connectivity is abnormal in ASD. The aim of this study was to examine whether brain connectivity in individuals with ASD was abnormal during visual-spatial information processing. Individuals with ASD and control participants completed a mental rotation task during functional magnetic resonance imaging (MRI) scanning, whereby two 3D shapes were judged to be the same (Same Trials) or mirror imaged (Mirror Trials). Control participants were slower at detecting mirror-imaged pairs than same pairs whereas the ASD group completed the two trial types at similar speeds. In the ASD group, mental rotation was associated with a marked reduction in brain activity and a highly abnormal connectivity between numerous brain regions. Relative to controls, the ASD group showed reduced connectivity or opposite patterns of connectivity between pairs of brain regions. In terms of connectivity, the two groups showed a very different response to an increase in task difficulty. During more challenging Mirror Trials, controls tended to increase connections between certain brain regions, whereas the ASD group appeared to suppress connections between these regions. There was an interesting exception to this pattern in the visual cortex, a finding that may suggest that the ASD group has an advantage in the early processing of visual stimuli. Overall, this study has identified a novel abnormality of visuospatial processing in ASD that is associated with aberrant neural connectivity and that may stem from enhanced visual perceptual processing. © 2012 INSAR/Wiley Periodicals, Inc.
Article citation: Autism Res 2012, 5: 314–330. DOI: 10.1002/aur.1245
Atypical Cry Acoustics in 6-Month-Old Infants at Risk for Autism Spectrum Disorder
Stephen J. Sheinkopf, Jana M. Iverson, Melissa L. Rinaldi, and Barry M. Lester
This study examined ways in which infants at risk for autism produced cries as compared with the cries of low-risk infants. Recordings of babies’ cries were excerpted from vocal recordings of 6-month-old infants at risk for autism spectrum disorder (ASD) and low-risk infants. Infants were considered to be at risk for ASD if they had an older sibling with a confirmed ASD diagnosis. These cry recordings were then analyzed using a computer-based system designed for this purpose. Cries were categorized as either pain-related or non-pain-related based on observations of the videotapes. At-risk infants produced pain-related cries with higher and more variable fundamental frequency (commonly referred to as “pitch”) as compared with low-risk infants. A small number of the at-risk infants were later diagnosed with an ASD at 36 months of age. The cries for these babies had among the highest fundamental frequency values and also differed in other acoustic characteristics. These results provide preliminary evidence that alterations in cry production may be part of an atypical vocal signature of autism in early life. © 2012 INSAR/Wiley Periodicals, Inc.
Article citation: Autism Res 2012, 5: 331–339. DOI: 10.1002/aur.1244
Children With Autism Show Reduced Somatosensory Response: An MEG Study
Elysa J. Marco, Kasra Khatibi, Susanna S. Hill, Bryna Siegel, Monica S. Arroyo, Anne F. Dowling, John M. Neuhaus, Elliott H. Sherr, Leighton N. B. Hinkley, and Srikantan S. Nagarajan
Autism spectrum disorders are reported to affect nearly one of every 100 children, with over 90% of these children showing behavioral disturbances related to the processing of basic sensory information. Behavioral sensitivity to light touch, such as profound discomfort with clothing tags and physical contact, is a ubiquitous finding in children on the autism spectrum. In this study, we investigate the strength and timing of brain activity in response to simple, light taps to the fingertip. Our results suggest that children with autism show a diminished early response in the primary somatosensory cortex (S1). This finding is most evident in the left hemisphere. In exploratory analysis, we also show that tactile sensory behavior, as measured by the sensory profile, may be a better predictor of the intensity and timing of brain activity related to touch than a clinical autism diagnosis. We report that children with atypical tactile behavior have significantly lower amplitude somatosensory cortical responses in both hemispheres. Thus, sensory behavioral phenotype appears to be a more powerful strategy for investigating neural activity in this cohort. This study provides evidence for atypical brain activity during sensory processing in autistic children and suggests that our sensory behavior-based methodology may be an important approach to investigating brain activity in people with autism and neurodevelopmental disorders. © 2012 INSAR/Wiley Periodicals, Inc.
Article citation: Autism Res 2012, 5: 340–351. DOI: 10.1002/aur.1247
A Perceptual–Motor Deficit Predicts Social and Communicative Impairments in Individuals With Autism Spectrum Disorders
Sally A. Linkenauger, Matthew D. Lerner, Verónica C. Ramenzoni, and Dennis R. Proffitt
People with autism spectrum disorders (ASDs) have known difficulties with social interaction and motor skills (e.g. clumsiness). It has long been thought that these difficulties may emerge from a common perceptual problem; the identification of which could improve understanding of how such difficulties come about and create new treatment targets. The ability to understand at how one's body may interact with the seen physical environment has been speculated to be such a problem, although this has not been directly tested. Crucially, this ability has shown to respond to training in other populations, making it a potentially fruitful treatment target. This study compared two groups of people with ASDs with age-matched typically developing controls in their ability to understand how their bodies may interact with their environments. Results showed an unprecedented degree of difficulty among those with ASDs in understanding and anticipating how they might be able to interact with standard objects. Moreover, the degree of this difficulty was very strongly related to parent-reported social/communicative challenges across the lifetime. Thus, this study suggests that social/communicative challenges in ASDs may stem from difficulties in a basic ability to integrate one's body with the seen physical environment. This difficulty may affect the ability to maintain and calibrate the relationship between oneself and the social and physical environments. As the ability to understand how one's body interacts with the environment can be taught, this study suggests that it may be a fruitful new target for treatments meant to address core challenges among those with ASDs. © 2012 INSAR/Wiley Periodicals, Inc.
Article citation: Autism Res 2012, 5: 352–362. DOI: 10.1002/aur.1248
Using Eye Movements as an Index of Implicit Face Recognition in Autism Spectrum Disorder
Darren Hedley, Robyn Young, and Neil Brewer
Individuals with an autism spectrum disorder (ASD) are often reported to be worse at face recognition than persons without an ASD. Performance has usually been assessed using overt, explicit recognition tasks where individuals are asked whether or not they recognize a familiar or studied face. Here, we recorded eye movements of participants with and without an ASD while they viewed a studied face, and we compared these with eye movements recorded during the viewing of a new, unfamiliar face. We argued that any differences in eye movements between the studied and new faces would provide an indication of implicit, or unconscious, memory processes and face recognition. Face recognition was also assessed by explicitly asking the participants if they recognized the face they had studied. We also manipulated the view of some faces by changing the pose and lighting, and by masking the image with visual noise. Participants with ASD performed worse than controls on the explicit recognition task. Eye movement-based measures, however, indicated that unconscious face recognition and memory processes may not be affected to the same degree as explicit recognition. © 2012 INSAR/Wiley Periodicals, Inc.
Article citation: Autism Res 2012, 5: 363–379. DOI: 10.1002/aur.1246