Document Detail  Twin-singleton differences in brain structure
using structural equation modelling. MedLine Citation: PMID: 
11844738     Owner:  NLM     Status:  MEDLINE     Twin studies
are important to investigate genetic influences on variation in
human brain morphology in health and disease. However, the twin
method has been criticized for its alleged non-generalizability
due to differences in the intrauterine and family environment of
twins, compared with singletons. To test whether twin-singleton
differences complicate interpretation of genetic contributions
on variation in brain volume, brains from 112 pairs of twins and
34 of their siblings with a mean (standard deviation) age of
30.7 (9.6) years were scanned using MRI. The influence of birth
order, zygosity and twin-sibling differences on brain volume
measures was analysed using maximum-likelihood model fitting.
Variances were homogeneous across birth order, zygosity and
twin-singleton status. Irrespective of zygosity, intracranial
volume was smalle