Genetics of electroencephalographic coherence and intelligence in young twins²

G. Caroline M. van Baal¹, Dorret I. Boomsma¹, and Eco J.C. de Geus<sup>1

1</sup>Vrije Univ, Department Biological Psychology, Amsterdam

The search for genes influencing cognitive abilities can be aided by the use of intermediate phenotypes. Essential requirements for such research is that both phenotypes as well as the association between them show high heritabilities. An important advantage of using an intermediate phenotype is that it may guide in finding the psychophysiological mechanisms underlying cognition. Unfortunately, research in this area has not yet shown substantial successes, with possible exceptions of speed of information parameters such as inspection time, reaction times and P300 event related potentials. In the current study we focus on another possible mechanism, namely neuronal connectivity of the brain, as indexed by coherence in the electroencephalogram (EEG). EEG coherence is a measure of cross-correlation between EEG recordings at different sites on the scalp. It expresses a developmental pattern that closely relates to changes in cognitive abilities in young children. To study the association between cognition and coherence, EEG and IQ data were collected twice for 209 five-to-seven-year-old twin pairs. Both phenotypes show substantial heritabilities (D.I. Boomsma and G.C.M. van Baal, 1998, Devel.Neuropsych. 14, 115-126; G.C.M. van Baal, E.J.C. de Geus, D.I. Boomsma, 1998, Behav. Genet. 28, 9-19). Phenotypic correlations between total IQ or performal IQ scores and EEG coherences with and within the prefrontal cortex were low but significant (-.15). The origins of these correlations will be further explored.

²Supported by NWO-575-65-052 and Van Coeverden Adriani Stichting