The Japanese journal of neuropsychology

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ArticleTitle	Default-mode network and cognitive dysfunctions: a role of posterior cingulate cortex in attention and memory
Language	J
AuthorList	Keisuke Takahata¹⁾²⁾, Motoichiro Kato²⁾
Affiliation	¹⁾Clinical Neuroimaging Team, Molecular Neuroimaging Group, Molecular Imaging Center, National Institute of Radiological Sciences ²⁾Department of Neuropsychiatry, Keio University School of Medicine
Publication	Japanese Journal of Neuropsychology: 30 (4), 259-267, 2014
Received
Accepted
Abstract	Default-mode network (DMN) is a brain structure that consisted of posterior cingulate cortex, precuneus, medial prefrontal cortex, medial parietal cortex, inferior parietal cortex and hippocampal formation. Early activation studies with cognitive tasks showed these cortical areas are engaged in episodic memory, envisioning future, theory of mind, stimulus-independent thoughts and monitoring external environment. However, recent studies revealed DMN is associated with wider varieties of cognitive processes, demonstrating that not only activation but also deactivation of DMN are indispensable for efficient relocation of cognitive resources. In this paper, we reviewed various neuroimaging findings and relevant theories that try to explain putative functions of DMN. First, we looked back the history of identification of DMN, and described how methodological progress in neuroimaging studies shaped the concept of DMN. Second, we discussed characterizations of DMN as one of large-scale brain networks. A novel method such as graph theoretical analysis enabled characterization of structure of a large-scale brain network. These studies support a spatial overlap between cortical hub regions and DMN. Third, we reviewed empirical literature that investigated a role of deactivation of DMN in cognitive processes. There are ample evidence supporting a causal role of deactivation of DMN in sustained attention and memory encoding/retrieval. Especially, finding from studies of attentional lapse and encoding/retrieval flip suggested that a competitive relationship between DMN and task-positive network is a potential locus of cognitive dysfunction of attention deficit hyperactivity disorder and Alzheimer's disease. We discuss the implication of these findings for our understanding of the clinical significance of DMN. Finally, we introduce an integrative model that highlights function of default-mode network.
Keywords	default-mode network, deactivation, posterior cingulate cortex, attention deficit hyperactivity disorder, Alzheimer's disease