This study compared magnetoencephalographic (MEG) imaging-derived indices of auditory and somatosensory cortical processing in children aged 8–12 years with autism spectrum disorder (ASD; N = 18), those with sensory processing dysfunction (SPD; N = 13) who do not meet ASD criteria, and typically developing control (TDC; N = 19) participants. The magnitude of responses to both auditory and tactile stimulation was comparable across all three groups; however, the M200 latency response from the left auditory cortex was significantly delayed in the ASD group relative to both the TDC and SPD groups, whereas the somatosensory response of the ASD group was only delayed relative to TDC participants. The SPD group did not significantly differ from either group in terms of somatosensory latency, suggesting that participants with SPD may have an intermediate phenotype between ASD and TDC with regard to somatosensory processing. For the ASD group, correlation analyses indicated that the left M200 latency delay was significantly associated with performance on the WISC-IV Verbal Comprehension Index as well as the DSTP Acoustic-Linguistic index. Further, these cortical auditory response delays were not associated with somatosensory cortical response delays or cognitive processing speed in the ASD group, suggesting that auditory delays in ASD are domain specific rather than associated with generalized processing delays. The specificity of these auditory delays to the ASD group, in addition to their correlation with verbal abilities, suggests that auditory sensory dysfunction may be implicated in communication symptoms in ASD, motivating further research aimed at understanding the impact of sensory dysfunction on the developing brain.

Atypical corpus callosum size and functional connectivity have been repeatedly implicated in autism spectrum disorders (ASDs). Conversely, individuals with agenesis of the corpus callosum often present with diagnostic features characteristic of autism. An emerging literature has identified genetic and environmental factors which may contribute to both ASD symptomatology and the neuroanatomic finding of altered white matter in the corpus callosum. In this review, we consider what is known about the structure and function of the corpus callosum and provide an update on research identifying corpus callosum abnormalities in individuals with ASD. We also review the literature on behaviors characteristic of autism that are observed in individuals with agenesis of the corpus callosum in an effort to identify some of the neuropathology that is likely to be associated with these behaviors. Finally, we suggest a conceptual model of 'sensory processing inefficiency' for future research aimed at elucidating some of the phenotypic variation in individuals with social communication challenges. KEYWORDS• autism • corpus callosum agenesis • language • neuroimaging • repetitive behaviors • restricted interests • sensory processing • social behavior Atypical corpus callosum size and connectivity have been repeatedly implicated in autism spectrum disorders (ASD). Reflection on the functional sequelae of corpus callosum abnormalities can further our understanding of the neural networks that support social communication beginning at the level of stimulus registration, to integration of information and finally behavioral response. We suggest that impaired interhemispheric communication, mediated by the corpus callosum, contributes to information processing inefficiency. This inefficient processing can impact social communication not only by the way of failure to integrate fast-paced, socially relevant information, but also in the temporal mismatch that can develop in a social dyad between individuals with intact versus impaired information processing. Furthermore, abnormal interhemispheric communication may adversely impact the development of functional organization (i.e., hemispheric specialization for language), further overloading an impaired cognitive processing system. Many individuals with isolated agenesis of the corpus callosum (AgCC), the congenital absence of this key white matter conduit, display traits of autism (or meet full diagnostic criteria) and provide a model for investigating the role of the corpus callosum in neurodevelopment. Specifically, the investigation of cognitive, behavioral and sensory functioning in this population offers a unique window for examining the role of interhemispheric transfer and inhibition in the development of language and social skills.For reprint orders, please contact: reprints@futuremedicine.com