The similarity of brain morphology in healthy monozygotic twins

Aim of the study was to investigate the degree of similarity of twin brains with respect to their outer shape and gyrification. High resolution MRI was obtained from 26 healthy monozygotic twins (MZ) and three-dimensional renderings of the brains were generated. Similarity was rated by human investigators and by computer analysis. Three different image types were analyzed: whole-brain views, silhouettes and a bird's-eye view of a segment showing the central region. For each of the three image types, 13 tasks (identifying the related twin-pair out of a set of five brains) had to be solved by the human raters. For whole brain, views and silhouettes 66/91(p<0.005) and for segment views 44/91 (p<0.02) correct identifications were made. Using cross correlation coefficients, the computer-based analysis as well significantly often identified related twins. Again correct identification was more likely based on whole-brain views and silhouettes than on segment views of the central region. In conclusion, we found that overall brain shape is probably strongly influenced by genetic effects but the variation in sulcal and gyral patterns is also affected by non-genetic influences to a considerable extent.