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The topographic ambiguity and reference-dependency that has plagued EEG/ERP research throughout its history are largely attributable to volume conduction, which may be concisely described by a vector form of Ohm’s Law. This biophysical relationship is common to popular algorithms that infer neuronal generators via inverse solutions. It may be further simplified as Poisson’s source equation, which identifies underlying current generators from estimates of the second spatial derivative of the field potential (Laplacian transformation). Intracranial current source density (CSD) studies have dissected the “cortical dipole” into intracortical sources and sinks, corresponding to physiologically-meaningful patterns of neuronal activity at a sublaminar resolution, much of which is locally cancelled (i.e., closed field). By virtue of the macroscopic scale of the scalp-recorded EEG, a surface Laplacian reflects the radial projections of these underlying currents, representing a unique, unambiguous measure of neuronal activity at scalp. Although the surface Laplacian requires minimal assumptions compared to complex, model-sensitive inverses, the resulting waveform topographies faithfully summarize and simplify essential constraints that must be placed on putative generators of a scalp potential topography, even if they arise from deep or partially-closed fields. CSD methods thereby provide a global empirical and biophysical context for generator localization, spanning scales from intracortical to scalp recordings.

Objective: Definition of appropriate frequency bands and choice of recording reference limit the interpretability of quantitative EEG, which may be further compromised by distorted topographies or inverted hemispheric asymmetries when employing conventional (non-linear) power spectra. In contrast, fPCA factors conform to the spectral structure of empirical data, and a surface Laplacian (2-dimensional CSD) simplifies topographies by minimizing volume-conducted activity. Conciseness and interpretability of EEG and CSD fPCA solutions were compared for three common scaling methods. Methods: Resting EEG and CSD (30 channels, nose reference, eyes open/closed) from 51 healthy and 93 clinically-depressed adults were simplified as power, log power, and amplitude spectra, and summarized using unrestricted, Varimax-rotated, covariance-based fPCA. Results: Multiple alpha factors were separable from artifact and reproducible across subgroups. Power spectra produced numerous, sharplydefined factors emphasizing low frequencies. Log power spectra produced fewer, broader factors emphasizing high frequencies. Solutions for amplitude spectra showed optimal intermediate tuning, particularly when derived from CSD rather than EEG spectra. These solutions were topographically distinct, detecting multiple posterior alpha generators but excluding the dorsal surface of the frontal lobes. Instead a low alpha/theta factor showed a secondary topography along the frontal midline. Conclusions: CSD amplitude spectrum fPCA solutions provide simpler, reference-independent measures that more directly reflect neuronal activity. Significance: A new quantitative EEG approach affording spectral components is developed that closely parallels the concept of an ERP component in the temporal domain.

Background-There is growing evidence that individual differences among depressed patients on electrophysiologic (EEG), neuroimaging, and neurocognitive measures are predictive of therapeutic response to antidepressants. This study replicates prior findings of pretreatment differences between SSRI responders and nonresponders in EEG alpha power or asymmetry, and examines whether these differences normalize or are stable following treatment.

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Objective Previously the authors found that personal importance of religion or spirituality was associated with a lower risk for major depression in a study of adults with and without a history of depression. Here the authors examine the association of personal importance of religion or spirituality with major depression in the adult offspring of the original sample using a 10-year prospective longitudinal design. Method Participants were 114 adult offspring of depressed and nondepressed parents, followed longitudinally. The analysis covers the period from the 10-year to the 20-year follow-up assessments. Diagnosis was assessed with the Schedule for Affective Disorders and Schizophrenia–Lifetime Version. Religiosity measures included personal importance of religion or spirituality, frequency of attendance at religious services, and denomination (all participants were Catholic or Protestant). In a logistic regression analysis, major depression at 20 years was used as the outcome measure and the three religiosity variables at 10 years as predictors. Results Offspring who reported at year 10 that religion or spirituality was highly important to them had about one-fourth the risk of experiencing major depression between years 10 and 20 compared with other participants. Religious attendance and denomination did not significantly predict this outcome. The effect was most pronounced among offspring at high risk for depression by virtue of having a depressed parent; in this group, those who reported a high importance of religion or spirituality had about one-tenth the risk of experiencing major depression between years 10 and 20 compared with those who did not. The protective effect was found primarily against recurrence rather than onset of depression. Conclusions A high self-report rating of the importance of religion or spirituality may have a protective effect against recurrence of depression, particularly in adults with a history of parental depression.