The Relationship Between Temperament and Brain Development in Infant Siblings with Autism Spectrum Disorder

Background:

Differences in temperament profiles are already present at 6 months in infants who develop autism spectrum disorder (ASD) and are some of the disorder’s earliest behavioral signs (Zwaigenbaum et al., 2005; del Rosario et al., 2013; Paterson et al., 2014).  Brain imaging in these same infants has revealed that differences in white matter development are also present by 6 months (Wolff et al., 2012).  However, the relationship between brain development and temperament in infants at risk for ASD has yet to be examined. 

Objectives:  

Given the correspondence of timing of these atypical brain and behavioral phenomena, we aimed to characterize the association between white matter structural connectivity and individual differences in temperament at 6 and 12 months in infant siblings who received a diagnosis of ASD at age two years.

Methods:  

Thirty-seven infants who developed ASD (HRPos) and eighty-three infants with typically developing siblings (LR) were assessed longitudinally in a larger, multi-site study of brain and behavioral development in ASD. Temperament was assessed at 6 and 12 months using the IBQ-R (Gartstein & Rothbart, 2003).  Diffusion tensor imaging data were collected during natural sleep. Five white matter pathways were selected and deterministically segmented in common atlas space (see Verde et al. 2014).  These were the: genu of the corpus callosum, uncinate fasciculus, cingulum, superior cerebellar peduncle (SCP) and the anterior limb of the internal capsule (ALIC). Microstructure was characterized by fractional anisotropy (FA).  The relationships between three aspects of temperament: Surgency, Regulatory Control, and Negative Affect, and FA in five white matter fiber pathways at 6 and 12 months were examined using Pearson correlations.

Results:  

Preliminary analyses found no correlations between white matter pathways and temperament concurrently at 6 months. However, significant concurrent correlations between white matter and temperament were found at 12 months in both groups. In addition, correlations were found between 6-month white matter microstructure and 12-month temperament data, between higher FA in the genu and higher negative affect,(r = .044, p<.05), FA in the SCP at 6 mo and  decreased surgency at 12 mo in the HRPos group (r = -.047, p<.01), and between FA in the cingulum at 6 months and Negative Affect at 12 month in the low risk group (r =.033, p<.01).

Conclusions:

These data suggest that there are indeed relationships between neurobiology and temperament in infants at high risk for ASD.  Brain differences at 6 months correlate with behavior at 12 months, but concurrent relationships are not yet present at 6 months, probably because there is not yet enough variability in temperament. Tracts such as the uncinate, which links the anterior temporal lobe with the orbito-frontal cortex, are likely to play a role in self-control and orienting behavior. These are important for aspects of temperament such as regulatory capacity. These findings of differences in neurobiology and temperament appear before many of the major symptoms of ASD and are likely to have important implications for the development of the disorder. Further examination of a larger dataset is underway and will include trajectory analysis.