In search of the depressive self: extended medial prefrontal network during self-referential processing in major depression.

Major depression is associated with an excessive self-focus, a tendency to engage oneself in self-referential processing. The medial frontal gyrus (MFG) is central to self-referential processing. This study aimed to explore the neural bases of this excessive self-focus and to disambiguate the role of the MFG in the pathophysiology of major depression. We presented 15 depressed patients and 15 healthy subjects with personality traits during functional magnetic resonance imaging and asked them to judge whether each trait described them ('self' condition) or a generally desirable trait ('general' condition). Both patients and healthy subjects activated the MFG in 'self' vs 'general' condition. However, the activation of the dorsal part of the MFG and of the dorsolateral prefrontal cortex (DLPFC) in 'self' vs 'general' condition was unique to patients. Additionally, patients displayed an increased functional connectivity between the MFG, the dorsal anterior cingulate cortex and the DLPFC. These results provide evidence for an extended medial prefrontal network during self-referential processing in major depression, suggesting the involvement of a greater cognitive control.

Can voxel based morphometry, manual segmentation and automated segmentation equally detect hippocampal volume differences in acute depression?

CONTEXT: According to meta-analyses, depression is associated with a smaller hippocampus. Most magnetic resonance imaging (MRI) studies among middle aged acute depressed patients are based on manual segmentation of the hippocampus. Few studies used automated methods such as voxel-based morphometry (VBM) or automated segmentation that can overcome certain drawbacks of manual segmentation (essentially intra- and inter-rater variability and operator time consumption). OBJECTIVE: The aim of our study was to compare the sensitivity of manual segmentation, automated segmentation and VBM to detect hippocampal structural changes in middle aged acute depressed population. METHOD: Twenty-one middle aged depressed inpatients and 21 matched controls were compared regarding their hippocampal structure using VBM with SPM5, manual segmentation and an automated segmentation algorithm. The VBM-ROI analysis was performed using two different normalization methods: the standard approach implemented in SPM5 and the most recent DARTEL algorithm. RESULTS: Using VBM-DARTEL, when corrected for multiple comparisons, significant volume differences were detected between groups in different regions and more specifically in hippocampus with ROI analyses. Whereas using standard VBM (without DARTEL), ROI analyses did not show bilateral volume between group differences. Significant hippocampal volume reductions between patients and controls were also detected using manual segmentation (-11.6% volume reduction, p<0.05) and automated segmentation (-9.7% volume reduction, p<0.05). VBM-DARTEL and automated segmentation show equal sensitivity in detecting hippocampal differences in depressed patients, while standard VBM was unable to detect hippocampal changes. Both VBM-DARTEL and automated segmentation could be used to perform large scale volumetric studies in humans. The new automated segmentation technique could further explore and detect hippocampal subpart differences that could be very useful for clarifying physiopathology of psychiatric disorders.

Verbal memory performance of patients with a first depressive episode and patients with unipolar and bipolar recurrent depression.

Depression is usually associated with episodic memory impairment. The main clinical features of depression associated with that memory impairment are not clearly defined. The main goal of that study was to assess the role of the diagnostic subtypes and the number of depressive episodes on the memory performance of acute unipolar (UP) and bipolar (BP) depressed patients.Twenty-three patients with a first major depressive episode (FE), 28 patients meeting DSM-IV criteria for UP recurrent depression (UR) and 18 BP patients with recurrent depression were compared with 88 healthy subjects on a verbal episodic memory task. Patients suffering from a first depressive episode did not show verbal memory impairment as compared to normal controls. Unlike FE patients, UR and BP patients exhibited verbal memory deficits with impaired free recall and normal cued recall and recognition. The memory deficits of the UR and BP patients was present in the first free recall trial. Depressed patients improved their memory performance across the three trials of the task at the same rate than normal controls. Our results suggest that the number of depressive episodes has a negative influence on verbal memory performance of acute depressed patients. The effects of the repetition of the depressive episodes are not modulated by the subtypes of depression and may reflect sensitization to the cognitive impact of depression associated with increasing prefrontal dysfunction.