Electroencephalographic Pattern, Beta Frequency, Quantitative Trait Locus

Description

Since the initial discovery of the human electroencephalogram (EEG) by Berger (1929), it has been speculated that neural oscillations play a broad role in nervous systems and form the basis for higher cognitive functions and consciousness. The presence of a beta/gamma oscillation (18 to 50 Hz) is thought to represent an activated state of the underlying neuronal network. These beta (12-29 Hz) and gamma (30-50 Hz) brain rhythms involve gamma-aminobutyric acid type A (GABA-A) receptor action (Haenschel et al., 2000; summary by Porjesz et al., 2002).

Inheritance

Stassen et al. (1988) reviewed the evidence on the genetically determined component of the resting electroencephalogram. They concluded that the individual characteristics of the resting EEG are primarily determined by genetic factors for the following reasons: with respect to their EEGs, monozygotic twins are only slightly less like one another than each person is to himself over time; the average within-pair EEG similarity in dizygotic twins is significantly above the interindividual EEG similarity between unrelated persons; and the EEGs of monozygotic twins reared apart are as similar to each other as are the EEGs of the same person over time.

Van Beijsterveldt et al. (1996) measured the EEG in 91 MZ and 122 DZ twins, aged 16 years. The EEG was recorded on 14 scalp positions during quiet resting with eyes closed; spectral powers were calculated for 4 frequency bands: delta, theta, alpha, and beta. Twin correlations pointed toward high genetic influences for all these powers and scalp locations. The largest part of the variants in the EEG was explained by additive genetic factors. The average heritabilities for the delta (1.5-3.5 Hz), theta (4.0-7.5 Hz), alpha (8.0-12.5 Hz), and beta (13-25 Hz) frequencies were 76%, 89%, 89%, and 86%, respectively. Multivariate analyses suggested that the same genes for EEG alpha rhythm are expressed in different brain areas in the left and right hemisphere. Thus, the authors concluded that brain functioning, as indexed by rhythmic brain-electrical activity, is one of the most heritable characteristics in humans.

Mapping

To identify genes underlying the heritability of EEG, Porjesz et al. (2002) conducted a linkage and linkage-disequilibrium study concerning the 3 beta frequency bands (13 to 28 Hz) of the human EEG. Their studies demonstrated maximum lod scores with the GABRB1 gene (137190) on chromosome 4p13-p12 between markers D4S1627 and D4S1645. The linkage-disequilibrium analysis indicated that a quantitative trait locus for the beta EEG phenotype is located in or near the GABRB1 gene.