Heritability of background EEG across the power spectrum

Abstract

We estimated the genetic and nongenetic (environmental) contributions to individual differences in the background EEG power spectrum in two age cohorts with mean ages of 26.2 and 49.4 years. Nineteen-lead EEG was recorded with eyes closed from 142 monozygotic and 167 dizygotic twin pairs and their siblings, totaling 760 subjects. We obtained power spectra in 24 bins of 1 Hz ranging from 1.0 to 25.0 Hz. Generally, heritability was highest around the alpha peak frequency and lower in the theta and delta bands. In the beta band heritability gradually decreased with increasing frequency, especially in the temporal regions. Genetic correlations between power in the classical broad bands indicated that half to three-quarters of the genetic variance can be attributed to a common source. We conclude that across the scalp and most of the frequency spectrum, individual differences in adult EEG are largely determined by genetic factors.Descriptors: Twin study, Temporal stability, Heritability, Genetic correlationRecordings of resting background EEG show striking interindividual differences (Vogel, 2000). In part, these differences can be described in a qualitative way, for example, the presence or absence of low-voltage EEG, defined as resting EEG without rhythmic activity and with low amplitude that occurs in about 4% of the adult population or, at the other extreme, the presence of continuous alpha waves in an estimated proportion of also about 4% of the adult population (Vogel, 1970). More common, however, is the quantitative description of the individual differences in the EEG traces by the amplitude or power spectrum.Background EEG power has been linked with various forms of psychopathology. For example, increased theta power and theta/beta ratio is found in Attention Deficit Hyperactivity Disorder (Barry, Clarke, & Johnstone, 2003;Bresnahan & Barry, 2002;Chabot & Serfontein, 1996;Clarke, Barry, McCarthy, & Selikowitz, 2001;Clarke et al., 2003;Jasper, Solomon, & Bradley, 1938;Monastra et al., 1999;Satterfield, Cantwell, Saul, Lesser, & Podosin, 1973), and increased beta power is found in (a predisposition to) alcoholism (Ehlers & Schuckit, 1990, 1991Gabrielli et al., 1982;Propping, 1977;Rangaswamy et al., 2002;Van Sweden & Niedermeyer, 1999;Vogel, 2000). Therefore, understanding interindividual variance in EEG power could provide clues to the underlying neurobiology of these disorders.A first step is the partitioning of interindividual variance in EEG power into genetic and environmental parts. This can be done in twin studies that compare the intrapair resemblance between two types of sibling relationships, namely genetically identical (monozygotic twins, MZ) and nonidentical twins (dizygotic twins, DZ). If MZ resemblance for EEG power is higher than DZ resemblance, this constitutes evidence for genetic influences on the EEG. A simple formula by Falconer (1960) computes the relative contribution of genetic influences to the total variance, also called heritability (h 2 ), as twice the difference in MZ/DZ rese...

Electrophysiological predictors of clinical response to antidepressants

“…Test-retest reliability of alpha power was high at both frontal and posterior sites (r ≥ .92), and is comparable to that found for healthy adults for retest periods over one year (Smit et al, 2005). Elevated alpha has also been found in depressed patients in a euthymic state (Pollock & Schneider, 1989), which suggests that it reflects a stable biological trait in patients who respond favorably to antidepressants.…”

“…(Smit et al, 2005) and depressed patients (Allen et al, 2004;Bruder et al, 2008). Auditory evoked potentials likewise have high reliability in healthy adults and depressed patients.…”

Phenotypic and genetic correlations between evoked EEG/ERP measures during the response anticipation period of a delayed response task

“…For upper alpha synchronization, heritability varied from 35% to 65%, and for theta desynchronization, heritability ranged from 31% to 50%. These estimates are lower than heritability of resting state oscillatory power in the same bands (Smit et al, 2005) but similar to other evoked responses such as the P300 and N1 (Anokhin, Heath, & Myers, 2004;Smit et al, 2007aSmit et al, , 2007bvan Beijsterveldt and van Baal, 2002). Note that genetic contribution to SCP was localized mainly in the right frontal, left parietal-central, and occipital areas, but for upper alpha synchronization and theta desynchronization, no clear topographic pattern in heritability could be distinguished.…”

“…The EEG sample in this study was derived from an ongoing twin family study on cognition (e.g., Posthuma, Neale, Boomsma, & de Geus, 2001;Smit et al, 2005Smit et al, , 2008Smit, Posthuma, Boomsma, & de Geus, 2007a, 2007b in twins and family members from the Netherlands Twin Registry (Boomsma, Vink, et al, 2002). It consisted of 760 subjects from 309 families divided into two age cohorts based on the age of the twins: a younger cohort (M 5 26.2 years, SD 5 4.1) and a middle-aged cohort (M 5 49.4 years, SD 5 7.2).…”

“…Second, because variation in EEG/ERP measures tends to be under strong genetic control (e.g., Smit, Posthuma, Boomsma, & de Geus, 2005;Smit, Posthuma, Boomsma, & de Geus, 2007a;Smit, Stam, Posthuma, Boomsma, & de Geus, 2008;van Beijsterveldt & van Baal, 2002), we tested whether heritability of the three ERP/EEG measures could be explained by a common genetic factor. Third, in keeping with the idea that challenges to the system tend to increase genetic variance (de Geus, Kupper, Boomsma, & Snieder, 2007), heritability of the ERP/ EEG measures were examined under two levels of task difficulty: a low and a high memory load condition.…”