Alterations in aperiodic neural activity associated with major depressive disorder.

Historically, aperiodic neural activity (i.e., the 1/f exponent and offset of electroencephalogram (EEG) power spectra) has been treated as neural noise. However, recent work has highlighted associations among aperiodic activity, aging, cognition, and psychopathology. While depression has been associated with cognitive deficits and dysregulation of excitatory/inhibitory neural mechanisms linked to aperiodic activity, to date, few studies have compared aperiodic activity in adults with and without depression, and none have evaluated aperiodic activity as a function of depressive chronicity. Here, individuals with depression (n=72) and healthy controls (n=34) completed a resting state EEG recording from which aperiodic activity estimates were extracted. We show significant group differences in aperiodic exponent and offset across central and posterior regions, such that, as hypothesized, these parameters were lower for depressed individuals relative to controls. Follow-up analyses clarified that this effect was driven by the number of lifetime depressive episodes experienced. Future research is needed to understand how depression heterogeneity impacts aperiodic activity.