a1 Institute of Psychiatry, King's College London, UK
a2 University of Pittsburgh, School of Medicine, Department of Psychiatry, Pittsburgh, PA, USA
a3 University Department of Psychiatry, Royal Victoria Infirmary, Newcastle upon Tyne, UK
Background A mood-congruent sensitivity towards negative stimuli has been associated with development and maintenance of major depressive disorder (MDD). The emotional Stroop task assesses interference effects arising from the conflict of emotional expressions consistent with disorder-specific self-schemata and cognitive colour-naming instructions. Functional neuroimaging studies of the emotional Stroop effect advocate a critical involvement of the anterior cingulate cortex (ACC) during these processes.
Method Subjects were 17 medication-free individuals with unipolar MDD in an acute depressive episode (mean age 39 years), and 17 age-, gender- and IQ-matched healthy volunteers. In an emotional Stroop task, sad and neutral words were presented in various colours, and subjects were required to name the colour of words whilst undergoing functional magnetic resonance imaging (fMRI). Overt verbal responses were acquired with a clustered fMRI acquisition sequence.
Results Individuals with depression showed greater increases in response time from neutral to sad words relative to controls. fMRI data showed a significant engagement of left rostral ACC (BA 32) and right precuneus during sad words in patients relative to controls. Additionally, rostral ACC activation was positively correlated with latencies of negative words in MDD patients. Healthy controls did not have any regions of increased activation compared to MDD patients.
Conclusions These findings provide evidence for a behavioural and neural emotional Stroop effect in MDD and highlight the importance of the ACC during monitoring of conflicting cognitive processes and mood-congruent processing in depression.
(Received March 26 2006)
(Revised July 05 2007)
(Accepted July 11 2007)
(Online publication September 10 2007)
c1 Address for correspondence: M. Mitterschiffthaler, Ph.D., Neuroimaging Research Group, Clinical Neuroscience, PO Box 89; Institute of Psychiatry, De Crespigny Park, London SE5 8AF, UK. (Email: firstname.lastname@example.org)