Posterior EEG alpha at rest and during task performance: Comparison of current source density and field potential measures

Abstract

Resting and task-related EEG alpha are used in studies of cognition and psychopathogy. Although Laplacian methods have been applied, apprehensions about loss of global activity dissuade researchers from greater use except as a supplement to reference-dependent measures. The unfortunate result has been continued reliance on reference strategies that differ across labs, and a systemic preference for a montage-dependent average reference over true reference-free measures. We addressed these concerns by comparing resting- and task-related EEG alpha using three EEG transformations: nose- (NR) and average-referenced (AR) EEG, and the corresponding CSD. Amplitude spectra of resting and prestimulus task-related EEG (novelty oddball) and event-related spectral perturbations were scaled to equate each transformation. Alpha measures quantified for 8-12 Hz bands were: 1) net amplitude (eyes-closed minus eyes-open) and 2) overall amplitude (eyes-closed plus eyes-open); 3) task amplitude (prestimulus baseline) and 4) task event-related desynchronization (ERD). Mean topographies unambiguously represented posterior alpha for overall, net and task, as well as poststimulus alpha ERD. Topographies were similar for the three transformations, but differed in dispersion, CSD being sharpest and NR most broadly distributed. Transformations also differed in scale, AR showing less attenuation or spurious secondary maxima at anterior sites, consistent with simulations of distributed posterior generators. Posterior task alpha and alpha ERD were positively correlated with overall alpha, but not with net alpha. CSD topographies consistently and appropriately represented posterior EEG alpha for all measures.

Association of posterior EEG alpha with prioritization of religion or spirituality: A replication and extension at 20-year follow-up

“…The present report extends the time scale of this linkage by an additional ten years in a larger, mostly independent sample of participants. Moreover, by virtue of using a substantially denser EEG montage (72 vs. 13 sites), the effects could be unequivocally matched the unique neuronal generator pattern identified with posterior EEG alpha (Tenke et al, 2011, 2015). …”

“…These limiting conditions (i.e. floor and ceiling effects) offer at least a partial explanation for the observation that prestimulus task-related alpha (auditory novelty oddball) was strongly correlated with overall alpha, but negatively correlated with net alpha (Tenke et al, 2015). This distinction is particularly important because early R/S Importance was an indicator for overall alpha, rather than net alpha, in this and our previous study (Tenke et al, 2013).…”

“…However, systematic comparisons of resting alpha for reference-dependent (nose, average) EEG with reference-free surface Laplacian or current source density (CSD) transformations have demonstrated considerable pitfalls for spectra derived from surface potentials (SP) that are effectively counteracted by CSD (Kayser and Tenke, 2006, 2015a,b; Tenke and Kayser, 2005, 2015). Compared to SP spectra, CSD spectra not only have sharper topographies (Tenke et al, 2015) but also provide the more consistent and appropriate representation of distributed posterior generators in simulation (Tenke & Kayser, 2015), and thereby yield more reliable estimates of alpha activity at scalp. We found that overall posterior CSD alpha during rest is strongly correlated with prestimulus alpha in a novelty oddball task (Tenke et al, 2015), suggesting that posterior alpha may reflect a stable individual trait that cuts across task boundaries or experimental protocols.…”

“…Compared to SP spectra, CSD spectra not only have sharper topographies (Tenke et al, 2015) but also provide the more consistent and appropriate representation of distributed posterior generators in simulation (Tenke & Kayser, 2015), and thereby yield more reliable estimates of alpha activity at scalp. We found that overall posterior CSD alpha during rest is strongly correlated with prestimulus alpha in a novelty oddball task (Tenke et al, 2015), suggesting that posterior alpha may reflect a stable individual trait that cuts across task boundaries or experimental protocols. Even though posterior alpha has been associated with a family history of MDD (Bruder et al, 2005), it remains to be determined to what extent posterior alpha is (1) related to a vulnerability to depression, (2) a predictor of treatment outcome, or (3) an initial vulnerability that is linked to a subsequent propensity toward recovery.…”

Motivated attention and family risk for depression: Neuronal generator patterns at scalp elicited by lateralized aversive pictures reveal blunted emotional responsivity

“…Furthermore, structural imaging measures suggested greater cortical thinning over right posterior cortex in children at high versus low risk (Peterson et al, 2009), and alpha was inversely related to cortical thickness, although not directly to alpha asymmetry (Bruder et al, 2012). While these findings are intriguing, the relationship of resting to task-related alpha (e.g., Tenke et al, 2015), or between structural and functional brain measures, is complex and as of yet not fully understood, necessitating the use of more targeted paradigms and measures. A recent MEG study employing the steady-state visual evoked fields technique reported a robust emotional modulation of rTPJ activity in 15 healthy women and 20 clinically-depressed women without a family history of depression; however, this modulation was markedly reduced in 8 depressed patients having at least one parent with a recurrent MDD diagnosis (Moratti et al, 2015).…”