RESEARCH ARTICLE


Brain Activation During Autobiographical Memory Retrieval with Special Reference to Default Mode Network



Tadashi Inoa, *, Ryusuke Nakaib, Takashi Azumab, Toru Kimuraa, Hidenao Fukuyamac
a Department of Neurology, Rakuwakai-Otowa Hospital, Otowachinjicho 2, Yamashina-ku, Kyoto 607-8062, Japan
b Research Center for Nano Medical Engineering, Institute for Frontier Medical Sciences, Kyoto University. Shogoin, Sakyo-ku, Kyoto 606-8507, Japan
c Department of Brain Pathophysiology, Human Brain Research Center, Graduate School of Medicine, Kyoto University, Shogoin, Sakyo, Kyoto, 606-8507, Japan


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© Ino et al; Licensee Bentham Open

open-access license: This is an open access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted, non-commercial use, distribution and reproduction in any medium, provided the work is properly cited.

* Address correspondence to this author at the Department of Neurology, Rakuwakai-Otowa Hospital, Otowachinjicho 2, Yamashina-ku, Kyoto 607-8062, Japan; Tel: +81-75-593-4111; Fax: +81-75-581-6935; E-mail: rakuwadr042@rakuwadr.com


Abstract

Recent neuroimaging studies have suggested that brain regions activated during retrieval of autobiographical memory (ABM) overlap with the default mode network (DMN), which shows greater activation during rest than cognitively demanding tasks and is considered to be involved in self-referential processing. However, detailed overlap and segregation between ABM and DMN remain unclear. This fMRI study focuses first on revealing components of the DMN which are related to ABM and those which are unrelated to ABM, and second on extracting the neural bases which are specifically devoted to ABM. Brain activities relative to rest during three tasks matched in task difficulty assessed by reaction time were investigated by fMRI; category cued recall from ABM, category cued recall from semantic memory, and number counting task. We delineated the overlap between the regions that showed less activation during semantic memory and number counting relative to rest, which correspond to the DMN, and the areas that showed greater or less activation during ABM relative to rest. ABM-specific activation was defined as the overlap between the contrast of ABM versus rest and the contrast of ABM versus semantic memory. The fMRI results showed that greater activation as well as less activation during ABM relative to rest overlapped considerably with the DMN, indicating that the DMN is segregated to the regions which are functionally related to ABM and the regions which are unrelated to ABM. ABM-specific activation was observed in the left-lateralized brain regions and most of them fell within the DMN.

Keywords: Autobiographical memory, semantic memory, default mode network, functional MRI.