Objectives: In the current study, we sought to examine whether infants who go on to develop ASD symptoms show different patterns of visual orienting at 6 months of age when compared to low-risk infants and genetic high-risk infants who do not develop ASD symptoms. If so, does the organizational integrity of white matter explain atypical visual orienting?
Methods: We used risk status and ADOS scores at 24 months to form three discrete groups; genetic low-risk or typically developing infants (hereafter LR, n = 37), genetic high-risk infants who do not meet ADOS criteria for an ASD at 24 months (hereafter HR-, n = 28), and infants who meet ADOS classification for an ASD at 24 months (hereafter ASD, n = 14). At 6 months of age, visual orienting data was extracted from a gap/overlap paradigm and imaging data was extracted from a Diffusion Tensor Imaging sequence. The three groups did not significantly differ in age (p = 0.297), nonverbal developmental level (p = 0.789), or number of valid gap (p = 0.306) or overlap trials (p = 0.148) completed.
Results: A disease specific pattern emerged for the overlap latencies such that the ASD group showed longer latencies than both the HR- (p = 0.013) and the LR group (p = 0.038), who were statistically equivalent. The data revealed a disease continuum model in gap latencies such that the ASD group showed significantly longer latencies than the LR group, but the HR- group did not significantly differ from the LR or ASD groups and their latencies fell at an intermediate position between LR and ASD (e.g., ASD > HR- > LR). We found that the organizational integrity of white matter (RD) in the splenium moderated the association between risk status and visual orienting (overlap latencies, as per the disease specific finding above). The results revealed a disordinal interaction, F(2, 65) = 3.35, p = .041, such that latencies in the overlap condition were not related to white matter integrity in the ASD group, whereas the association between overlap latencies and splenium RD among LR infants was quite strong.
Conclusions: These findings suggest that patterns of visual orienting at 6 months differentiate infants who go on to develop characteristics of ASD at 24 months from LR infants and HR infants who do not develop ASD symptoms, and that microstructural integrity of the splenium is putatively involved in this process.
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