title: Distinct genetic influences on cortical surface area and cortical thickness.
abstract: Neuroimaging studies examining the effects of aging and neuropsychiatric disorders on the cerebral cortex have largely been based on measures of cortical volume. Given that cortical volume is a product of thickness and surface area, it is plausible that measures of volume capture at least 2 distinct sets of genetic influences. The present study aims to examine the genetic relationships between measures of cortical surface area and thickness. Participants were men in the Vietnam Era Twin Study of Aging (110 monozygotic pairs and 92 dizygotic pairs). Mean age was 55.8 years (range: 51-59). Bivariate twin analyses were utilized in order to estimate the heritability of cortical surface area and thickness, as well as their degree of genetic overlap. Total cortical surface area and average cortical thickness were both highly heritable (0.89 and 0.81, respectively) but were essentially unrelated genetically (genetic correlation = 0.08). This pattern was similar at the lobar and regional levels of analysis. These results demonstrate that cortical volume measures combine at least 2 distinct sources of genetic influences. We conclude that using volume in a genetically informative study, or as an endophenotype for a disorder, may confound the underlying genetic architecture of brain structure.
authors.affiliation: Department of Psychiatry, University of California, San Diego, La Jolla, CA 92093, USA. mspanizz@ucsd.edu
authors.forename: Matthew S
authors.initials: MS
authors.lastname: Panizzon
authors.forename: Christine
authors.initials: C
authors.lastname: Fennema-Notestine
authors.forename: Lisa T
authors.initials: LT
authors.lastname: Eyler
authors.forename: Terry L
authors.initials: TL
authors.lastname: Jernigan
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Prom-Wormley
authors.forename: Michael
authors.initials: M
authors.lastname: Neale
authors.forename: Kristen
authors.initials: K
authors.lastname: Jacobson
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Lyons
authors.forename: Michael D
authors.initials: MD
authors.lastname: Grant
authors.forename: Carol E
authors.initials: CE
authors.lastname: Franz
authors.forename: Hong
authors.initials: H
authors.lastname: Xian
authors.forename: Ming
authors.initials: M
authors.lastname: Tsuang
authors.forename: Bruce
authors.initials: B
authors.lastname: Fischl
authors.forename: Larry
authors.initials: L
authors.lastname: Seidman
authors.forename: Anders
authors.initials: A
authors.lastname: Dale
authors.forename: William S
authors.initials: WS
authors.lastname: Kremen
mesh_terms: D002540:Cerebral Cortex / Q000033:anatomy & histology* / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009929:Organ Size / Q000235:genetics; D014427:Twins / Q000235:genetics*