Department of Psychiatry, University of Western Ontario, Ontario N6A 3H8, Canada.
Psychiatry Clin Neurosci. 2009 Dec;63(6):754-61. doi: 10.1111/j.1440-1819.2009.02030.x.
Reports on resting brain activity in healthy controls have described a default-mode network (DMN) and important differences in DMN connectivity have emerged for several psychiatric conditions. No study to date, however, has investigated resting-state DMN in relatively early depression before years of medication treatment. The objective of the present study was, therefore, to investigate the DMN in patients seeking help from specialized mental health services for the first time for symptoms of depression.
Fourteen depressed subjects and 15 matched controls were scanned using 4-T functional magnetic resonance imaging while resting with eyes closed. All but one subject was medication free. A precuneus/posterior cingulate cortex (P/PCC) seed-region connectivity analysis was used to identify the DMN and compare study groups in regions of relevance to depression.
The P/PCC analysis identified the DMN well in both study groups, consistent with prior literature. Direct comparison showed significantly reduced correlation between the P/PCC and the bilateral caudate in depression compared with controls and no areas of increased connectivity in the depressed group.
The present study is the first to investigate resting-state DMN in the early stages of treatment-seeking for depression. Depressed subjects had decreased connectivity between the P/PCC and the bilateral caudate, regions known to be involved in motivation and reward processing. Deficits in DMN connectivity with the caudate may be an early manifestation of major depressive disorder.
健康对照组静息态脑活动的报告描述了默认模式网络（DMN），并且几种精神疾病的 DMN 连接出现了重要差异。然而，迄今为止，尚无研究在接受多年药物治疗之前的抑郁症早期阶段研究静息状态 DMN。因此，本研究的目的是调查首次因抑郁症状寻求专门的心理健康服务的患者的 DMN。
使用 4-T 功能磁共振成像对 14 名抑郁患者和 15 名匹配的对照组进行扫描，患者闭眼静息。除了一名患者外，其余患者均未服用药物。使用后扣带回/后扣带皮层（P/PCC）种子区域连接分析来识别 DMN，并比较与抑郁相关的研究组的区域。
P/PCC 分析在两组研究对象中均能很好地识别 DMN，与先前的文献一致。直接比较显示，与对照组相比，抑郁组 P/PCC 与双侧尾状核之间的相关性明显降低，而抑郁组无连接增加的区域。
本研究是首次在寻求治疗的抑郁早期阶段研究静息状态 DMN。抑郁患者的 P/PCC 与双侧尾状核之间的连接减少，尾状核是已知参与动机和奖励处理的区域。与尾状核的 DMN 连接缺陷可能是重性抑郁障碍的早期表现。
