Anterior cingulate theta activity is associated with degree of treatment response in major depression

Abstract

Background: The anterior cingulate cortex (ACC), a functionally heterogeneous region, has attracted considerable attention in depression research. Whereas dorsal ACC hypoactivity has been observed in depression, rostral ACC hyperactivity has been associated with better treatment response. Using electroencephalographic (EEG) imaging techniques, we tested whether rostral ACC activity during a depressive episode predicted later treatment response. Since the ACC has been suggested as a possible neuronal generator for theta activity, the effect was hypothesized to emerge only within this band. Methods: Thirty-minute, 28-channel resting EEG data were recorded in 18 unmedicated subjects with major depression and 18 matched, control subjects. For depressed subjects, clinical outcome was assessed 4–6 months later, after nortriptyline treatment. Adopting a median split strategy, pre-treatment EEG data of those subjects with relatively better ( n=9) and worse ( n=9) treatment response were compared using low resolution electromagnetic tomography (LORETA), which computed three-dimensional cortical current density for classical EEG frequency bands using a Talairach brain atlas. Results: Consistent with our predictions, better treatment response was uniquely associated with hyperactivity (higher theta) in the rostral ACC (BA 24/32). Conclusions: The present results replicate prior hemodynamic findings implicating the rostral ACC for treatment response in depression with an electrophysiological imaging technique.