No abstract

Major depression has been associated with anomalous activation in the subgenual anterior cingulate cortex, but its response to emotional stimuli is poorly understood. The primary goal of this study was to compare levels of activation in the subgenual anterior cingulate cortex of diagnosed depressed and nondepressed participants in response to happy and sad facial expressions of affect. Whereas cognitive theories of depression predict increased activation to negative stimuli, depressed participants were found to exhibit increased activation to both types of stimuli in the subgenual anterior cingulate cortex. Importantly, the loci were in different regions of the subgenual anterior cingulate cortex, suggesting that there is functional specialization in the processing of negatively and positively valenced stimuli.

Behavioral studies suggest that emotional reactivity in depressed persons predicts subsequent symptom reduction. Using functional magnetic resonance imaging in a prospective study, we show that greater amygdala activation to emotional facial expressions among depressed patients predicts symptom reduction 8 months later, controlling for initial depression severity and medication status. Functional magnetic resonance imaging may thus be used as a method to identify neural markers in depressed patients at risk for poor outcome.

Depression involves either enhanced processing of negative stimuli or diminished processing of positive stimuli. We used functional magnetic resonance imaging to assess brain activation in depressed vs healthy participants. Fifteen participants diagnosed with major depressive disorder and 15 controls were scanned during a lexical decision task involving neutral, happy, sad, and threat-related words. For happy words, depressed subjects exhibited less activation than did controls to happy words in fronto-temporal and limbic regions. For sad words, depressed subjects showed more activation than did controls in the inferior parietal lobule and less activation in the superior temporal gyrus and cerebellum, suggesting a complex activation pattern that varies for neural sub-circuits that may be associated with di¡erent cognitive or behavioral processes. INTRODUCTIONCognitive theories of depression have focused primarily on enhanced processing of negative stimuli as an explanation for the etiology and maintenance of depression [1,2]. Consistent with these formulations, depressed subjects have been found to exhibit faster responses to negative stimuli than they do to neutral or positive stimuli [3,4]. A different conceptualization of depression focuses on the absence of positive affect [5]. Consistent with this perspective, studies of depressed individuals have documented significantly diminished responsiveness to positive (but not negative) stimuli [6,7].Taken together, depression appears to be associated with increased processing of negative stimuli and/or diminished processing of positive stimuli. We used fMRI and a lexical decision task to address the question of whether these response biases are related to differential activation patterns between depressed and healthy control subjects. We predicted that, relative to normal controls, depressed participants would exhibit increased activation to sad (relative to neutral) words and/or decreased activation to happy (relative to neutral) words in brain regions associated with affective reactivity, attention, or single-word processing, such as the amygdala, insula, parietal lobules, and frontal and temporal cortical regions. SUBJECTS AND METHODSSubjects: Fifteen individuals with diagnosed major depressive disorder (MDD: 12 females, mean age 35.1 years) and 15 non-depressed control (12 females, mean age 30.7 years) subjects with no psychiatric history participated in this study. Seven of the depressed participants were taking antidepressant medications (two were taking tricyclic antidepressants, one was taking tricyclic and selective serotonin reuptake inhibitors (SSRI) antidepressants, and four were taking other types of antidepressants). There was no significant age difference between the groups. All participants were between the ages of 18 and 60, had no reported history of brain injury, lifetime history of primary psychotic ideations, social phobia, panic disorder or mania, no reported substance abuse within the past 6 months, no behavioral indications of possible impa...

The impact of traumatic experiences on cognitive processes, especially memory, is reviewed. The major psychological sequelae of trauma (reexperiencing, avoidance, hypervigilance) and posttraumatic stress disorder (PTSD) are noted and related to traditional views of fear conditioning. Evidence indicating enhanced memory for the gist of emotional events is reviewed as are psychological and neurophysiological mechanisms underlying this enhancement. This view is updated by introducing the distinction between explicit and implicit memory and its relevance to traumatic memory and PTSD. The central role of “the experiencing ego” in the storage and retrieval of episodic memories is postulated. This leads into discussion of dissociative experiences during traumas and the occasional amnesia for voluntary recall of the trauma accompanied by involuntary, uncontrollable flashbacks of it. The relationship of dissociative experiences to hypnotizability and to pathological reactions to traumas is discussed, although the interpretation of those correlations is questioned. The article concludes by noting that beyond conditioning of fear, traumas often violate and shake the victims' basic assumptions about the benevolence, justice, and meaningfulness of their physical and social worlds. Psychotherapy with trauma victims then needs to attend not only to extinguishing the victims' fear and feelings of extreme vulnerability, but also to rebuilding their basic beliefs about the relative benevolence of the world.