Frontolimbic neural circuitry at 6 months predicts individual differences in joint attention at 9 months

Abstract

Elucidating the neural basis of joint attention in infancy promises to yield important insights into the development of language and social cognition, and directly informs developmental models of autism. We describe a new method for evaluating responding to joint attention performance in infancy that highlights the 9- to 10-month period as a time interval of maximal individual differences. We then demonstrate that fractional anisotropy in the right uncinate fasciculus, a white matter fiber bundle connecting the amygdala to the ventral-medial prefrontal cortex and anterior temporal pole, measured in 6-month-olds predicts individual differences in responding to joint attention at 9 months of age. The white matter microstructure of the right uncinate was not related to receptive language ability at 9 months. These findings suggest that the development of core nonverbal social communication skills in infancy is largely supported by preceding developments within right lateralized frontotemporal brain systems.

Figure 1

Three-dimensional reconstructions of the white matter fiber tracts examined in the current study: red = uncinate fasciculi (UF), blue = inferior longitudinal fasciculi (ILF), grey = optic tract.

Figure 2a

Scatterplot representing the association between RJA performance and age in weeks with 95% confidence intervals.

Figure 2b

Scatterplot representing the association between intra-individual variability in RJA performance, indexed by the coefficient of variation, and age in weeks with 95% confidence intervals.

Figure 3

Histogram with normal curve representing individual differences in RJA performance among 9 and 10 month-olds (n=35).

Figure 4

Scatterplots representing the association between fractional anisotropy (along the abscissa) in the bilateral uncinate fasciculi, inferior longitudinal fasciculi, and optic nerves at 6 months and responding to joint attention (RJA) at 9 months (along the ordinate) with 95% confidence intervals (r = partial Pearson correlation coefficient, controlling for total brain volume at 6 months and chronological age during the behavioral assessment).