学習・長期記憶3 Learning and Long-term Memory 3
O2-8-6-1 マカクザル大脳記憶想起ネットワークの構造的モジュール分割は機能的な分離と対応する Modular structures within macaque memory retrieval network implement functional differentiation during serial probe recognition task ○宮本健太郎1, 長田貴宏1, 足立雄哉1, 松井鉄平1,2, 木村紘子1, 渡辺朋美1, 節家理恵子1, 宮下保司1,2 ○Kentaro Miyamoto1, Takahiro Osada1, Yusuke Adachi1, Teppei Matsui1,2, Hiroko M Kimura1, Tomomi Watanabe1, Rieko Setsuie1, Yasushi Miyashita1,2 東京大学大学院 医学系研究科 総合生理学1, 東京大学大学院 理学系研究科 物理2 Dept Physiol, Univ of Tokyo, Tokyo1, Dept Phys, Univ of Tokyo, Tokyo2 Posterior parietal cortex (PPC) is known as a collection of architectonic subdivisions, each of which is interconnected with different cortical areas outside PPC. However, it is unknown if this differentiation of network structure corresponds with disparate functions during tasks. Previously, we conducted monkey fMRI experiment using serial probe recognition task to find functional homologue of human retrieval-related network and reported 47 retrieval-related areas including two PPC sites, area PG/PGOp in inferior parietal lobule and area PEa/DIP in intraparietal sulcus (Miyamoto et al., 2012, 2013). In the present study, we found that the 47 areas are segregated into six modules by community detection analysis using modularity optimization of the functional connectivity of spontaneous BOLD activity taken from the same monkeys. The two PPC sites were embedded in distinct sub-networks: PG/PGOp overlapped monkey default-mode network, while PEa/DIP overlapped monkey fronto-parietal network. The gross activity of the two networks during retrieval was typified by the activities of the two PPC sites with differential serial probe recognition profiles, which showed primacy and recency effects, respectively. Double dissociations of psychophysiological interactions between the two PPC sites and hippocampus or visual cortex conformed with this network-level segregation. These results converged to reveal the correspondence between differentiation of network and function in PPC. Interspecies comparisons provided additional evidence of common neural substrates in monkey and human PPC detected by task-based fMRI. Miyamoto K, Osada T, Adachi Y, Matsui T, Kimura HM, Watanabe T, Miyashita Y (2012) Memory retrieval-related fMRI activity in the macaque posterior parietal cortex. Neuroscience 2012, O3-D-37-1. Miyamoto K, Osada T, Adachi Y, Matsui T, Kimura HM, Miyashita Y (2013) Functional differentiation of memory retrieval network in macaque posterior parietal cortex. Neuron, in press.	O2-8-6-2 目標達成できる人と三日坊主の神経基盤差 Neural substrate of making it through the goal ○細田千尋1, 田中観自4, 立川将5, 本田学3, 大須理英子1, 花川隆2 ○Chihiro Hosoda1, Kanji Tanaka4, Masaru Tatekawa5, Manabu Honda3, Rieko Osu1, Takashi Hanakawa2 株式会社国際電気通信基礎技術研究所脳情報研究所1, 国立精神・神経医療研究センター2, 国立精神・神経医療研究センター3, 東京大学先端科学技術研究センター4, 芝浦工業大学5 CNS, ATR, Kyoto1, DCFD, NCNP,2, IBIC, NCNP3, RCAST4, SIT5 A number of scientific neuroimaging studies have begun to characterize changes of gray matter (GM) or white matter (WM) microstructure in correlation with various human abilities. However, it remains unclear whether there is neuroanatomical signature related to the ability of achieving a behavioral goal. In the present study, we ran two experiments to examine neural differences between people who continue to make efforts toward a given goal and who do not. In each experiment, T1-weighted structural magnetic resonance image (MRI) and diffusion-weighted images (DWI) were obtained before tasks. In the first experiment, 45 native Japanese speakers (university students) participated in an e-learning program involving second language (L2) vocabulary for four months. Although all were initially motivated to study L2, 21 people failed to complete the training program. In the second experiment, 65 university students were asked to complete the Tower of Hanoi task without time limitation. As a result, 34 subjects completed the most challenging level of the task in the experiment whereas 31 subjects opted not to do so. In both experiments, there were no significant differences in the intelligence quotient, motivation, or personal traits between the finishers and the non-finishers. However, in both experiments, the GM volume of the frontal pole and fractional anisotropy of the white matter beneath it were greater in the finishers than the non-finishers. Moreover, using an anatomical mask of the frontal pole, we discovered increment of GM volume of the frontal pole only in the finishers after completing the 4-month L2 training. This result suggests that the effort to achieve the goal might have induced plastic changes of the frontal pole GM volume.The present findings provide the first evidence that the structure of the frontal pole is linked with the ability of completing tasks and that this neural trait may be nurtured by continuing the effort to achieve the goal.
O2-8-6-3 代数方程式を解く際の左下前頭回の役割 The role of the left inferior frontal gyrus for solving algebraic equations ○中井智也1, 宮下紘幸1, 酒井邦嘉1 ○Tomoya Nakai1, Hiroyuki Miyashita1, Kuniyoshi L Sakai1 東京大学大学院　総合文化研究科　広域科学専攻1 Dept. of Basic Sci., Grad. Sch. of Arts and Sciences, Univ. of Tokyo, Tokyo1 Algebraic equations have tree-structures, which are constructed by recursive computation with variables and operators. To solve an algebraic equation, a reconstruction of tree-structures becomes necessary in addition to the construction of tree-structures. In the present study, we prepared three tasks (Equation, Search, and Reverse) to segregate the effect of constructions and reconstructions of tree-structures. A task-indicating cue was presented for 1000 ms followed by an algebraic equation such as "(a - b ÷ c) × d = e". In the Equation, participants solved the equation in a given symbol (e.g., a), and remembered the order of operators in the answer obtained. In the Search, participants searched an operator which was computed first within the equation, and they converted that operator to its inverse operator (e.g., from + to -). In the Reverse, participants converted all operators to their inverse operators, and remembered them in a reverse order. The Equation required both the construction and reconstruction of tree-structures, while the Search required only the construction; the Reverse was used as a basic control. In the Equation - Reverse contrast, we found significantactivations in the bilateral inferior frontal gyri (IFG) and supramarginal gyri (SMG) (corrected P < 0.05). In the Equation - Search contrast, significant activations were found only in the left IFG. These results indicate the critical role of the left IFG for reconstructing tree-structures in algebraic equations.	O2-8-6-4 側頭頭頂葉のネットワークにおける領域間の課題関連機能的相関：新近性識別課題を用いた機能的磁気共鳴画像法による課題 Inter-regional task-related functional correlation in temporo-parietal networks: A functional MRI study of recency judgments ○廣瀬聡1, 木村紘子1, 國松聡2, 阿部修2, 大友邦2, 宮下保司1, 小西清貴1 ○Satoshi Hirose1, Hiroko M Kimura1, Akira Kunimatsu2, Osamu Abe2, Kuni Ohtomo2, Yasushi Miyashita1, Seiki Konishi1 東京大学医学部　統合生理学教室1, 東京大学医学部　放射線医学教室2 Department of Physiology, The Univ. of Tokyo School of Med., Tokyo, Japan1, Department of Radiology, The Univ. of Tokyo School of Med., Tokyo, Japan2 It is known that recency judgments, judgments of the temporal order of past events, can be achieved by at least two retrieval processes, relational and item-based. Our previous study have revealed that relational recency judgments involved the parahippocampal region and the lateral parietal region, and that item-based recency judgments involved the lateral temporal region and the other lateral parietal region. It has also been revealed that these temporal and parietal regions constitute resting-state functional connectivity (RSFC) networks. In order to test the functional significance of the networks, the present functional MRI study examined the task-related functional correlations of brain activity across subjects during episodic retrieval in the temporo-parietal networks. Direct contrast between relational and item-based recency judgments revealed prominent activations in multiple temporal and parietal regions, as revealed in our previous study. RSFC analysis revealed multiple temporo-parietal networks consistent with the previous study: the significant RSFC was observed between one parahippocampal region and one left lateral parietal region associated with relational recency judgments, and between four lateral temporal regions and another left lateral parietal region associated with item-based recency judgments. The significant task-related functional correlation was observed between the parahippocampal and the parietal region associated with relational recency judgments. As for item-based recency judgments, however, only one of the four RSFC networks showed significant task-related functional correlation. These results suggest that only a part of the temporo-parietal networks based on RSFC have functional significance, and that task-related functional correlation can be used for testing the RSFC networks for their relevance to particular psychological processes.

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