| Project/Area Number |
16K18373
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| Research Category |
Grant-in-Aid for Young Scientists (B)
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| Allocation Type | Multi-year Fund |
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| Research Field |
Neurophysiology / General neuroscience
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| Research Institution | Institute of Physical and Chemical Research |
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Principal Investigator |
陳 碩 国立研究開発法人理化学研究所, 脳科学総合研究センター, 研究員 (30772694)
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| Project Period (FY) |
2016-04-01 – 2017-03-31
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| Project Status |
Discontinued (Fiscal Year 2016)
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| Budget Amount *help |
¥4,160,000 (Direct Cost: ¥3,200,000、Indirect Cost: ¥960,000)
Fiscal Year 2017: ¥1,690,000 (Direct Cost: ¥1,300,000、Indirect Cost: ¥390,000)
Fiscal Year 2016: ¥2,470,000 (Direct Cost: ¥1,900,000、Indirect Cost: ¥570,000)
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| Keywords | Goal-directed navigation / Decision-making / Optogenetics / Neural circuits / Hippocampus / Hypothalamus / hippocampus / spatial navigation / optogenetics / electrophysiology |
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| Outline of Annual Research Achievements |
Decision-making during goal-directed navigation is a highly evolved behavior requiring a coordination of perception, learning and memory, and planning. In the past five months, by using an array of circuit interrogation techniques including viral tracing and optogenetics, we have successfully identified a crucial role of the neural circuit from hypothalamic supramammillary nucleus (SuM) to hippocampal dentate gyrus (DG) in mice performing a T-maze delayed non-match to sample task. This significant progress has filled the gap on a wide circuit map that bridge to the hippocampus for making decisions during spatial navigation.
At first, we performed brain-wide 3D mapping of SuM efferents by taking advantage of a SuM-Cre transgenic mouse line that allows specific expression of fluorescent proteins at SuM. After brain tissue clearing, high-resolution reconstruction of an atlas of SuM efferents was achieved, indicating strong projections from SuM to DG.
Next, we employed targeted optogenetics to test the function of SuM-DG circuit in goal-directed navigation. Cre-dependent channelrhodopsin-2 (ChR2) or archaerhodopsin (ArchT)-expressing adeno-associated virus (AAV) was injected to SuM. For the ChR2-transfected mice, application of 488 nm laser at DG terminals showed no effect on the task performance. However, when 532 nm laser was applied to the ArchT-transfected mice, we found a dramatic decline of the T-maze performance. This result clearly indicated that inhibition of the SuM-DG circuit impaired the animal’s spatial working memory during goal-directed navigation.
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