The present functional magnetic resonance imaging (fMRI) study investigated neural changes in relation to mood biased processing in depression, before and after cognitive behavioral therapy (CBT) using an emotional Stroop task.

Sixteen unmedicated patients (mean age 40 years), fulfilling DSM-IV diagnosis for unipolar major depression underwent fMRI, prior to and after 16 once-weekly sessions of CBT. Sixteen matched healthy volunteers were scanned at similar time intervals. In an emotional Stroop task negative and neutral words were presented in various colors and volunteers had to name the color of words. Latencies were recorded to determine behavioral emotional interference effects. MRI images were acquired using clustered image acquisition. Whole-brain and region of interest analysis examined the neural basis of interference and mood biased processing.

At baseline patients displayed increased latencies during color naming negative words, in comparison to neutral words and in relation to healthy volunteers. After treatment, latencies did not significantly differ between groups. With regard to neural activity, depressed patients showed increased activation at baseline in amygdala, dorsolateral prefrontal cortex (DLPFC), and ventrolateral prefrontal cortex (VLPFC), which normalized after CBT. Additionally, hyperactivation in the rostral anterior cingulate at baseline was positively correlated with symptom reduction after CBT.

Evidence was found for an emotional interference effect during acute states of depression which improved following CBT. The neural basis is associated with increased activity in the amygdala, DLPFC and VLPFC which normalized after treatment. CBT seems to affect behavioral biases and neural circuits involved in processing negative information.