. Author manuscript; available in PMC: 2017 Nov 1.

Published in final edited form as: Autism Res. 2016 Jun 8;9(11):1169–1182. doi: 10.1002/aur.1643

Table 4.

Parameter Estimates From Nonlinear Mixed Effects (Quadratic) Models Fitted to Total Cerebral Volume (TCV), Gray Matter, and White Matter Data for the Typically Developing (TD) Boys, and All Boys With Autism Spectrum Disorder (ASD). The MRI Data Were Collected at Time 1 (Mean Age 3.1 Years), 1 Year After Baseline at Time 2 (Mean Age 4.1 Years), and Approximately 1 Year Later at Time 3 (Mean 5.3 Years). For Each Quadratic Model, Age Was Centered at the Mean Age of Time 1 MRI Collection (37.1 Months)

Measure	Parameter (SE)	Group
Measure	Parameter (SE)	TD	ASD
TCV	Intercept (cm³)	991.08 (13.92)	1033.81 (7.37)^**
	Linear slope	3.86 (0.32)	4.09 (0.18)
	Quadratic slope	−0.039 (0.010)	−0.057 (0.005)
Gray matter	Intercept (cm³)	625.67 (8.11)	651.94 (4.27)^**
	Linear slope	1.52 (0.31)	1.45 (0.17)
	Quadratic slope	−0.042 (0.011)	−0.032 (0.006)
White matter	Intercept (cm³)	364.87 (5.82)	382.60 (3.06)^*
	Linear slope	2.23 (0.19)	2.34 (0.11)
	Quadratic slope	−0.005 (0.007)	−0.028 (0.003)^*

Note. Significant contrast between TD and ASD

P < 0.01,

^**

P < 0.001.