Sleep and Dream Patterns in Twins: Markov Analysis of a Genetic Trait

Abstract

As early as 1936, Davis and Davis [1] reported on the influence of heredity on electroencephalograms (EEGs) by the direct method of studying twins. The inheritance of monozygotic (MZ) twins would be similar while that of dizygotic (DZ) twins would have variable heredity the same as that of ordinary siblings. They found that the waking alpha rhythms from one MZ twin resembled those from the other as closely as the record of the same person on successive recordings. Raney [2] in studying lateral dominance of the EEG in MZ twins concluded that the EEGs of identical twins are more similar than those of unrelated children only when treated as a group. Lennox and Gibbs [3] studied EEGs of normal and epileptic twins and concluded that, although epilepsy per se was not hereditary, cerebral dysrhythmia was. They further suggested that the EEG could be used as evidence in decisions dealing with the zygosity of twins and in tracing the heredity of abnormal cerebral rhythms. Using the concept that characteristics which can be shown to appear regularly in MZ twins and irregularly in DZ twins as evidence of the hereditary nature of any given trait, Lennox, Gibbs, and Gibbs [4] studied the waking alpha tracings of MZ and DZ twins. The EEG records were judged identical in 85% of the cases in MZ twins and alike in only 5% of the DZ twin group. Vogel [5] analyzed various EEG traits in 208 pairs of twins and found good agreement in MZ twins. Tangheroni and Pardelli [6] reported complete identity of EEG tracings between MZ couples but rhythms of discordant frequency and morphology in DZ couples.