Genetic Influences on Human Brain Structure A Review of Brain Imaging Studies in Twins.pdf

REVIEW ARTICLE Genetic Influences on Human Brain Structure: A Review of Brain Imaging Studies in Twins Jiska S. Peper,1 Rachel M. Brouwer,1 Dorret I. Boomsma,2 Rene? S. Kahn,1 and Hilleke E. Hulshoff Pol1* 1Department of Psychiatry, Rudolf Magnus Institute of Neuroscience, University Medical Center Utrecht, A01.126, 3584 CX Utrecht, The Netherlands 2Department of Biological Psychology, Free University, Van der Boechorststraat 1, 1081 BT Amsterdam, The Netherlands Abstract: Twin studies suggest that variation in human brain volume is genetically influenced. The genes involved in human brain volume variation are still largely unknown, but several candidate genes have been suggested. An overview of structural Magnetic Resonance (brain) Imaging studies in twins is presented, which focuses on the influence of genetic factors on variation in healthy human brain vol- ume. Twin studies have shown that genetic effects varied regionally within the brain, with high herit- abilities of frontal lobe volumes (90–95%), moderate estimates in the hippocampus (40–69%), and envi- ronmental factors influencing several medial brain areas. High heritability estimates of brain structures were revealed for regional amounts of gray matter (density) in medial frontal cortex, Heschl’s gyrus, and postcentral gyrus. In addition, moderate to high heritabilities for densities of Broca’s area, anterior cingulate, hippocampus, amygdala, gray matter of the parahippocampal gyrus, and white matter of the superior occipitofrontal fasciculus were reported. The high heritability for (global) brain volumes, including the intracranium, total brain, cerebral gray, and white matter, seems to be present through- out life. Estimates of genetic and environmental influences on age-related changes in brain structure in children and adults await further longitudinal twin-studies. For prefrontal cortex volume, white matter, and hippocampus volumes, a number of candidate genes have been identified, whereas for other