The response-specific changes in EEG tomography (LORETA) after 1 and 4 weeks of treatment in patients with drug-resistant depression
Abstract
Previous studies of patients with unipolar depression have shown that depressive symptoms are caused by dysfunction of the limbic and frontal lobe regions and clinical response to treatment is associated with a reciprocal pattern of subcortical and limbic metabolic decreases and cortical increases. The aim of our study was to examine time-specific (1-week vs. baseline and 4-week vs. baseline) and response-specific (responders vs. non-responders) differences in brain electrical activities in patients with resistant depressive disorder.
Method: The subjects were 25 inpatients with treatment resistant depression. EEG data and response to treatment were monitored at baseline and after 1 and 4 weeks on an antidepressant treatment.
Low-resolution brain electromagnetic tomography (LORETA) was computed from spectrally analyzed EEG data, and differences between 1-week and 4-week treatment-induced changes in responders and non-responders were displayed as statistical parametric maps of voxel-by-voxel paired t-test. Results: There was an increase of excitatory beta current densities in the posterior cingulate and insula in the responder group, whereas a decrease in the posterior cingulate and increase in the subgenual part of anterior cingulate was observed in non-responders after 1 week of treatment.
An increase of inhibitory processes, observed after 4 week of treatment, was differently located in responders (the paralimbic regions and rostral anterior cingulate) and non-responders (posterior cingulate). The excitatory processes were increased in widespread neocortical regions in responders, whereas decrease in right parietal lobe was found in nonresponders.
Conclusion: Our results suggest that significantly different time-specific and response-specific changes in neuronal electrical activities exist after week 1 and 4 of an antidepressant therapy. These changes seem to be associated with later response-specific effects rather than types of antidepressant therapy.