  Recently, we reported an emotion self-regulation study (Zotev et al., 2020),
in which patients with major depressive disorder (MDD) used simultaneous
real-time fMRI and EEG neurofeedback (rtfMRI-EEG-nf) to upregulate two fMRI and
two EEG activity measures, relevant to MDD. The target measures included fMRI
activities of the left amygdala and left rostral anterior cingulate cortex, and
frontal EEG asymmetries in the alpha band (FAA) and high-beta band (FBA). Here
we apply the exact low resolution brain electromagnetic tomography (eLORETA) to
investigate EEG source activities during the rtfMRI-EEG-nf procedure. The
exploratory analyses reveal significant changes in hemispheric lateralities of
upper alpha and high-beta current source densities in the prefrontal regions,
consistent with upregulation of the FAA and FBA during the rtfMRI-EEG-nf task.
Similar laterality changes are observed for current source densities in the
amygdala. Prefrontal upper alpha current density changes show significant
negative correlations with anhedonia severity. Changes in prefrontal high-beta
current density are consistent with reduction in comorbid anxiety. Comparisons
with results of previous LORETA studies suggest that the rtfMRI-EEG-nf training
is beneficial to MDD patients, and may have the ability to correct functional
deficiencies associated with anhedonia and comorbid anxiety in MDD.
