Heritability of brain volume, surface area and shape: An MRI study in an extended pedigree of baboons

Abstract

To evaluate baboons (Papio hamadryas) as a primate model for the study of the genetic control of brain size and internal structure, we performed high resolution (<500 microm) magnetic resonance imaging on 109 pedigreed baboons. Quantitative genetic analysis of these MR images using a variance components approach indicates that native (untransformed) brain volume exhibits significant heritability among these baboons (h(2) = 0.52, P = 0.0049), with age and sex also accounting for substantial variation. Using global spatial normalization, we transformed all images to a standard population-specific reference, and recalculated the heritability of brain volume. The transformed images generated heritability estimates of h(2) = 0.82 (P = 0.00022) for total brain volume, h(2) = 0.86 (P = 0.0006) for cerebral volume, h(2) = 0.73 (P = 0.0069) for exposed surface area of the cerebrum and h(2) = 0.67 (P = 0.01) for gray matter volume. Regional differences in the genetic effects on brain structure were calculated using a voxel-based morphometry (VBM) approach. This analysis of regional variation shows that some areas of motor cortex and the superior temporal gyrus show relatively high heritability while other regions (e.g. superior parietal cortex) exhibit lower heritability. The general pattern of regional differences is similar to that observed in previous studies of humans. The present study demonstrates that there is substantial genetic variation underlying individual variation in brain size and structure among Papio baboons, and that broad patterns of genetic influence on variation in brain structure may be similar in baboons and humans.

Cortical Folding of the Primate Brain: An Interdisciplinary Examination of the Genetic Architecture, Modularity, and Evolvability of a Significant Neurological Trait in Pedigreed Baboons (GenusPapio)

“…These findings suggest that gyrification has a separate genetic basis from brain size, so the trend of increased folding in the primate lineage involves selective forces that have been working separately but in tandem with those increasing gross brain volume. While there has been extensive work examining changes in brain size among primates, cortical gyrification has a unique evolutionary history that has not yet been broadly explored.Previous studies using magnetic resonance (MR) imaging provide preliminary evidence for a heritable genetic component to cortical variation in the baboon population studied here, generally estimating the heritability of cortical morphological features as between 20 and 40% (Mahaney et al 1993;Rogers et al 2007;Kochunov et al 2010). As only 150 MR scans were previously available, however, precise genetic mapping was impossible.…”

Sulcal Depth-Position Profile Is a Genetically Mediated Neuroscientific Trait: Description and Characterization in the Central Sulcus

“…Global spatial normalization was used to reduce intersubject variability in global brain size, shape, and orientation by spatially registering all images to a Talairach-compliant population-based template using a nine parameter, affine, linear transformation (Kochunov et al, 2002). This lessened the impact of highly heritable variability in brain volume, focusing subsequent genetic analyses on regional variance of sulcal structures rather than variance associated with whole brain size (Rogers et al, 2007;. Last, all images were resliced to isotropic 800 m spacing using a 3D, 15 voxel wide sinc interpolation kernel.…”

Genetic basis in motor skill and hand preference for tool use in chimpanzees (Pan troglodytes)

“…Consistent with approaches used by others [48][49][50][51][52][53][54][55][56], to estimate heritability, we used the software package SOLAR [57]. SOLAR uses a variance components approach to estimate the polygenic component of variance when considering the entire pedigree (see [48,51,54]). We included sex, rearing history and age as covariates in the estimates of heritability to account for their influence on phenotypic variation.…”