Grandchildren at High and Low Risk for Depression Differ in EEG Measures of Regional Brain Asymmetry

Abstract

Background-Electrophysiologic studies have found abnormalities of alpha asymmetry in depressed adults and offspring of depressed parents, which have been hypothesized to be vulnerability markers of depression. Resting electroencephalogram (EEG) was measured in grandchildren participating in a multigenerational high-risk study.

Using the high-risk family design to identify biomarkers for major depression

“…For third generation, because of the two preceding generations, we compared subjects who had both a parent and a grandparent with MDD with those with either a parent or grandparent, or neither. Consistent with the patterns from the previous generation, Generation 3 offspring with two generations of loading for depression demonstrated greater alpha asymmetry, with relatively less right-than left-hemisphere activity, compared to those with neither a depressed parent nor a depressed grandparent [29] (figure 5b). This difference was present in the parietal region only in the resting (eyes-closed) state, and not in the frontal regions for any condition.…”

“…(b) Third-generation offspring (G3). Adapted with permission from Bruder et al [29]. Graphs illustrate mean alpha asymmetry (that is, difference between the right-hemispheric and left-hemispheric log alpha power) at frontal, central and parietal sites during eyes-closed conditions.…”

“…We illustrate these approaches in the sections that follow. We do not elaborate on methodological aspects, as these have largely been covered elsewhere [28][29][30][31][32], and are not our primary focus. Instead, we emphasize the translational elements of these studies, demonstrating how applying biological measures to the high-risk design can provide unique opportunities to examine risk factors for disease.…”

Frontal alpha asymmetry as a pathway to behavioural withdrawal in depression: Research findings and issues

“…In contrast, children with an elevated familial risk for depression but who also show greater relative left frontal activation (i.e., the opposite of the La>Ra finding for depressed individuals) have lower incidence of depression themselves [87]. Further to this finding, Bruder et al [88] reported that children whose parents or grandparents were depressed demonstrated greater Lα>Rα EEG asymmetry in the parietal (but not frontal) regions than offspring who did not have parents or grandparents who were depressed.…”

Atypical right hemispheric functioning in the euthymic state of bipolar affective disorder

“…This might also explain the increased right hemisphere involvement in BD euthymia in this study. Also resting encephalogram in children with both parents and grandparents diagnozed with major depressive disorder showed greater alpha asymmetry, with relatively less right than left hemisphere activity, compared with children at lower risk for depression (Bruder et al, 2007). Although atypical right hemisphere functioning seems to be a trait characteristic associated with BD and major depression disorder, it is unclear whether this atypical functional hemispheric asymmetry reflects dysfunction, or a compensatory/adaptive mechanism of these disorders.…”