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Table 2 Generalized additive mixed-effects models examining group and age-related changes in DTI metrics

From: Atypical development of white matter microstructure of the corpus callosum in males with autism: a longitudinal investigation

Longitudinal DTI changes  
  Group Age spline Age X group spline  
  Mean Estimate a P -value EDF F P -value EDF F P -value ICC
Genu FA
ASD and TDC 0.62 −3.12% 0.048 3.45 3.99 0.006 4.67 2.25 0.05 89.7%
ASD 0.61 - - 4.31 2.11 0.075 - - -  
TDC 0.63 - - 5.26 5.02 0.0002 - - -  
Body FA
ASD and TDC 0.61 −2.40% 0.001 3.99 8.95 **** 6.33 2.41 0.02 88.3%
ASD 0.61 - - 6.59 3.46 0.002 - - -  
TDC 0.62 - - 4.25 15.64 **** - - -  
Splenium FA
ASD and TDC 0.69 −2.27% 0.04 5.91 9.66 **** 1.00 0.19 0.66 81.1%
ASD 0.69 - - 6.65 6.89 **** - - -  
TDC 0.7 - - 3.67 11.54 **** - - -  
Genu MD
ASD and TDC 0.76 1.63% 0.46 3.60 8.06 **** 1.00 0.07 0.78 85.9%
ASD 0.76 - - 3.04 5.20 0.002 - - -  
TDC 0.75 - - 4.87 7.06 **** - - -  
Body MD
ASD and TDC 0.79 1.90% 0.23 3.49 6.39 0.0002 1.30 0.06 0.86 82.4%
ASD 0.79 - - 3.57 6.39 0.0002 - - -  
TDC 0.78 - - 3.06 12.13 **** - - -  
Splenium MD
ASD and TDC 0.77 1.89% 0.001 1.81 0.53 0.57 4.63 5.62 **** 83.0%
ASD 0.78 - - 4.58 8.25 **** - - -  
TDC 0.76 - - 2.96 1.63 0.18 - - -  
Genu RD
ASD and TDC 0.37 5.89% 0.23 3.52 3.91 0.006 3.38 1.50 0.21 87.8%
ASD 0.38 - - 3.80 2.75 0.03 - - -  
TDC 0.36 - - 4.87 5.89 0.00007 - - -  
Body RD
ASD and TDC 0.4 5.33% 0.08 3.89 7.46 0.00001 4.93 1.47 0.20 91.7%
ASD 0.4 - - 5.05 4.11 0.001 - - -  
TDC 0.38 - - 4.00 15.00 **** - - -  
Splenium RD
ASD and TDC 0.32 7.54% 0.01 4.72 7.92 **** 1.00 0.70 0.40 86.6%
ASD 0.33 - - 5.89 5.55 **** - - -  
TDC 0.31 - - 3.34 8.66 **** - - -  
Genu AD
ASD and TDC 1.38 −0.28% 0.60 3.99 5.53 0.0002 1.00 0.06 0.81 85.9%
ASD 1.38 - - 3.10 6.10 0.0004 - - -  
TDC 1.39 - - 1.87 8.58 0.0005 - - -  
Body AD
  1.48 −0.005% 0.08 1.00 4.22 0.04 2.19 2.01 0.13 56.6%
  1.48 - - 1.93 9.72 0.0001 - - -  
  1.48 - - 2.66 3.25 0.03 - - -  
Splenium AD
  1.55 0.35% 0.03 1.67 0.37 0.65 3.55 1.87 0.12 80.0%
  1.55 - - 3.47 2.64 0.04 - - -  
  1.54 - - 3.70 1.64 0.17 - - -  
  1. aFor the parametric group differences, the estimate is reported as the percent deviation in the ASD group compared to the TDC group with the corresponding P-value. For the age spline and the age-by-group splines, the estimated degrees of freedom (EDF), F-value, and P-values are reported. ****P-value <0.00005. AD, axial diffusivity; ASD, autism spectrum disorder; EDF, estimated degrees of freedom to assess smooth spline complexity; ICC, intra-class correlation coefficient; FA, fractional anisotropy; MD, mean diffusivity; RD, radial diffusivity; TDC, typically developing controls.