Department of Rehabilitation Psychology, Daegu University, Gyeongsan, Gyeongsangbuk-Do, 712-714, South Korea.
Neuroimage. 2012 Jul 16;61(4):966-77. doi: 10.1016/j.neuroimage.2012.03.025. Epub 2012 Mar 15.
Most internally oriented mental activities are known to strongly activate the default network, which includes remembering the past, future thinking and social cognition, and are heavily self-referential, and demanding of memory retrieval processes. Based on these observations and building on related findings from the literature, the present article proposed a simple, dual-subsystem model of the default network. The ability of the model to estimate brain activity during autobiographical memory (AM) retrieval and related reference conditions was then tested by performing a quantitative meta-analysis of relevant literature. The model divided the default network into two subsystems. The first, called the 'cortical midline subsystem (CMS)', was comprised of the anteromedial prefrontal cortex and posterior cingulate cortex, and primarily mediates self-referential processing. The other, termed the 'parieto-temporal subsystem (PTS)', included the inferior parietal lobule, medial temporal lobe and lateral temporal cortex, and mainly supports memory retrieval processes. The meta-analysis of AM retrieval contrasts yielded a double dissociation that was consistent with this model. First, CMS regions associated more with an AM>laboratory-based memory (LM) contrast than with an AM>rest contrast, confirming that these regions play more critical roles in self-referential processing than memory retrieval processes. Second, all three PTS regions showed a greater association with an AM>rest contrast than with an AM>LM contrast, confirming that their role in memory retrieval processes is greater than in self-referential processing. Although the present model is limited in scope, both in terms of anatomical and functional specifications, it integrates diverse processes such as self-referential processing, episodic and semantic memory and subsystem interface, and provides useful heuristics that can guide further research on fractionation of the default network.
大多数内向型的心理活动都被认为会强烈激活默认网络，包括回忆过去、未来思考和社会认知，这些活动都具有强烈的自我参照性，需要记忆检索过程。基于这些观察结果，并借鉴相关文献中的发现，本文提出了一个简单的默认网络双子系统模型。然后，通过对相关文献进行定量元分析，测试了该模型估计自传体记忆（AM）检索和相关参照条件下大脑活动的能力。该模型将默认网络分为两个子系统。第一个称为“皮质中线子系统（CMS）”，由前内侧前额叶皮层和后扣带回皮层组成，主要介导自我参照处理。另一个称为“顶颞子系统（PTS）”，包括下顶叶、内侧颞叶和外侧颞叶皮层，主要支持记忆检索过程。对 AM 检索对比的元分析产生了与该模型一致的双重分离。首先，CMS 区域与 AM>实验室记忆（LM）对比相关，而与 AM>休息对比不相关，这证实了这些区域在自我参照处理中比在记忆检索过程中发挥更关键的作用。其次，PTS 的三个区域与 AM>休息对比的相关性均大于 AM>LM 对比，这证实了它们在记忆检索过程中的作用大于自我参照处理。尽管目前的模型在解剖学和功能方面都有一定的局限性，但它整合了多种过程，如自我参照处理、情景和语义记忆以及子系统接口，并提供了有用的启发式方法，可以指导对默认网络的细分的进一步研究。
