Dichter Gabriel S, Felder Jennifer N, Smoski Moria J
Department of Psychiatry, University of North Carolina at Chapel Hill School of Medicine, CB# 3366, Chapel Hill, NC 27599-7160, United States.
J Affect Disord. 2009 Apr;114(1-3):131-42. doi: 10.1016/j.jad.2008.06.027. Epub 2008 Aug 15.
Unipolar major depressive disorder (MDD) is characterized by aberrant amygdala responses to sad stimuli and poor cognitive control, but the interactive effects of these impairments are poorly understood.
To evaluate brain activation in MDD in response to cognitive control stimuli embedded within sad and neutral contexts.
Fourteen adults with MDD and fifteen matched controls participated in a mixed block/event-related functional magnetic resonance imaging (fMRI) task that presented oddball target stimuli embedded within blocks of sad or neutral images.
Target events activated similar prefrontal brain regions in both groups. However, responses to target events embedded within blocks of emotional images revealed a clear group dissociation. During neutral blocks, the control group demonstrated greater activation to targets in the midfrontal gyrus and anterior cingulate relative to the MDD group, replicating previous findings of prefrontal hypo-activation in MDD samples to cognitive control stimuli. However, during sad blocks, the MDD group demonstrated greater activation in a number of prefrontal regions, including the mid-, inferior, and orbito-frontal gyri and the anterior cingulate, suggesting that relatively more prefrontal brain activation was required to disengage from the sad images to respond to the target events.
A larger sample size would have provided greater statistical power, and more standardized stimuli would have increased external validity.
This double dissociation of prefrontal responses to target events embedded within neutral and sad context suggests that MDD impacts not only responses to affective events, but extends to other cognitive processes carried out in the context of affective engagement. This implies that emotional reactivity to sad events in MDD may impact functioning more broadly than previously understood.
单相重度抑郁症（MDD）的特征是杏仁核对悲伤刺激的反应异常以及认知控制能力差，但对这些损伤的交互作用了解甚少。
评估MDD患者在悲伤和中性情境中对认知控制刺激的脑激活情况。
14名患有MDD的成年人和15名匹配的对照组参与者参加了一项混合块/事件相关功能磁共振成像（fMRI）任务，该任务呈现了嵌入悲伤或中性图像块中的异常目标刺激。
两组中目标事件激活了相似的前额叶脑区。然而，对嵌入情感图像块中的目标事件的反应显示出明显的组间差异。在中性图像块期间，相对于MDD组，对照组在额中回和前扣带回对目标的激活更强，这重复了先前在MDD样本中发现的前额叶对认知控制刺激激活不足的结果。然而，在悲伤图像块期间，MDD组在多个前额叶区域表现出更强的激活，包括额中回、额下回、眶额回和前扣带回，这表明从悲伤图像中脱离以对目标事件做出反应需要相对更多的前额叶脑激活。
更大的样本量会提供更大的统计效力，更标准化的刺激会提高外部效度。
前额叶对嵌入中性和悲伤情境中的目标事件反应的这种双重分离表明，MDD不仅影响对情感事件的反应，还扩展到在情感参与背景下进行的其他认知过程。这意味着MDD中对悲伤事件的情绪反应可能比以前理解的更广泛地影响功能。
