Table 2. Twin pair correlations (95% confidence intervals) and heritability estimates for total volumes of four cortical lobar regions, seven subcortical structures and intracranial volume (ICV).
| Region | Within twin pair intraclass correlations (95% CI) |  |
 |
 |
Covariates Significance | |
|---|---|---|---|---|---|---|
| MZ pairs (N = 93) | DZ pairs (N = 68) | |||||
| Cortical Lobar Regions | ||||||
| Frontal cortex | 0.79 (0.70,0.85) | 0.40 (0.35,0.57) | 0.78 (0.42,0.85) | 0.01 (0,0.35) | 0.21 (0.15,0.3) | sNSS |
| Temporal cortex | 0.75 (0.65,0.82) | 0.46 (0.33,0.62) | 0.58 (0.24,0.81) | 0.17 (0,0.49) | 0.25 (0.18,0.35) | sNSS |
| Parietal cortex | 0.70 (0.58,0.78) | 0.42 (0.30,0.59) | 0.55 (0.18,0.78) | 0.15 (0,0.48) | 0.30 (0.22,0.42) | sNSS |
| Occipital cortex | 0.70 (0.59,0.78) | 0.35 (0.29,0.48) | 0.70 (0.42,0.78) | 0.00 (0,0.25) | 0.30 (0.22,0.41) | sNSS |
| Subcortical structures | ||||||
| Nucleus accumbens | 0.65 (0.53,0.74) | 0.44 (0.28,0.61) | 0.42 (0.03,0.73) | 0.24 (0,0.57) | 0.35 (0.26,0.47) | sNSN |
| Amygdala | 0.61 (0.48,0.71) | 0.41 (0.26,0.58) | 0.41 (0.00,0.71) | 0.21 (0,0.56) | 0.39 (0.29,0.52) | sNSS |
| Caudate | 0.86 (0.79,0.90) | 0.52 (0.40,0.66) | 0.67 (0.39,0.89) | 0.19 (0,0.46) | 0.14 (0.1,0.21) | NsSS |
| Hippocampus | 0.73 (0.63,0.81) | 0.37 (0.31,0.47) | 0.73 (0.52,0.81) | 0.00 (0,0.19) | 0.27 (0.19,0.37) | sNSS |
| Pallidum | 0.49 (0.33,0.62) | 0.24 (0.17,0.40) | 0.49 (0.11,0.62) | 0.00 (0,0.32) | 0.51 (0.38,0.67) | sSNS |
| Putamen | 0.68 (0.55,0.77) | 0.34 (0.28,0.5) | 0.68 (0.32,0.77) | 0.00 (0,0.32) | 0.32 (0.23,0.45) | sNSS |
| Thalamus | 0.50 (0.35,0.63) | 0.25 (0.18,0.44) | 0.51 (0.07,0.63) | 0.00 (0,0.38) | 0.50 (0.37,0.65) | sNSS |
| ICV | 0.88 (0.83,0.91) | 0.48 (0.41,0.63) | 0.79 (0.50,0.91) | 0.09 (0,0.37) | 0.12 (0.09,0.17) | NSS* |
Univariate ACE model intra-class correlation (ICC) with 95% CI and heritability (95% CI) for total volumes (left plus right hemisphere) of four cortical lobar regions, seven subcortical structures and intracranial volume (ICV). All estimates were adjusted for different scanners, age, sex and ICV where appropriate. Last column indicates the significance of covariates. Significance of the p-value (p < 0.05) for any of the covariates age, sex (coded 1 for male and 0 for female), scanners (4 scanners coded with 3 dummy variables) and ICV in that order is indicated as a string; S = significant and beta >0; s = significant and beta <0; N = not significant and * = not applicable. Significance for scanners were coded as S if p < 0.05 for any one of the scanners, ignoring the direction of beta.