FY2021 Annual Report

Memory Research Unit
Assistant Professor Kazumasa Z. Tanaka

(From left to right) Kaz, Viviane, Damien, Yu-Ju, Hiroto, Nakamura-san, Lorena, Thato, Miyu, Minato, Ai


The Memory Research Unit aims to understand how memories are stored and used in the brain. The hippocampus, together with its related structures, plays a unique role in memories of past events. Nevertheless, its specific contribution remains unclear. Our unit aims to reveal the mechanism of memory by using multidisciplinary approaches in rodents.

During FY2021, we made substantial progress in our research projects. Some of these research projects will be presented in the Japan Neuroscience Society Annual Meeting (Neuro2022) held in Okinawa. Several new members joined the unit. Kaoru Ohayama (Staff Scientist) is an expert in electrophysiology, and is currently working on Neuropixels system to record the activity of hundreds of neurons simultaneously in freely moving mice. Ai Takahashi (Technical Staff) is an expert in electron microscopy imaging. She will reveal ultrastructural characteristics of dendritic/spine structures associated with memory. Thato Mokhothu passed the proposal defense, and she is now a Ph.D. candidate. She also published a review paper in Frontiers of Behavioral Neuroscience (Mokhothu* & Tanaka*, 2021), discussing the contribution of pathological high-frequency oscillations to epilepsy. Miyu Nambu, Yu-Ju Lin, and Josefine Reuschenbach wrote another review paper presenting a new perspective on heterogeneous memory traces (Nambu, Lin, Reuschenbach, and Tanaka, 2022, in press). Tomoka Yoseyama got accepted into OIST Ph.D. program, and she will start her new career step from September 2022. In Japan Neuroscience Society meeting 2021, her poster presentation received the Junior Investigator Poster Development Award. Moreover, Yuma Kajihara, who is co-supervised by Kenji Doya and Kaz Tanaka, received the Sasakawa SCientific Research Grant.


2021年度には研究プロジェクトに大きな進展が見られました。これらの成果は、2022年6月に開催される日本神経科学学会年次大会(Neuro2022)において発表されます。今年度は新しいメンバーの加入もありました。Kaoru Ohyama(スタッフサイエンティスト)は電気生理学の専門家で、自由に行動するマウス脳の数百個もの神経細胞の活動を同時に計測するNeuropixelsという技術の応用に取り組んでいます。髙橋愛(技術スタッフ)は電子顕微鏡の専門家で、記憶に関係した神経細胞の樹状突起やスパインの超微細構造を最新の技術を使って明らかにします。研究以外では、Thato Mokhothuがproposal defense試験を突破して博士候補生になりました。また彼女は、病的な高周波神経振動とてんかんに関する総説論文をFrontiers in Behavioral Neuroscience誌に発表しました(Mokhothu* & Tanaka*, 2021)。さらに、Miyu NambuとYu-Ju Lin, Josefine Reuschenbachは別の総説論文を執筆し、多様な記憶痕跡が果たす役割についての新たな見方を展開しました(Nambu, Lin, Reuschenbach, and Tanaka, 2022, in press)。Tomoka Yoseyamaは、OISTのPh.D.プログラムに合格し、2022年9月から博士課程学生になります。また、2021年の日本神経科学学会年次大会では、Tomokaのポスター発表がJunior Investigator Poster Development Awardを受賞しました。さらに、Doya unitとco-supervisionを受けるYuma Kajihara (Ph.D. student)が笹川研究助成金を受賞しました。

1. Staff

  • Damien Mercier, Staff Scientist (Feb. 2020-)
  • Hiroto Ashitomi, Technician (Mar. 2020-)
  • Keiko Nakamura, Research Unit Administrator
  • Viviane Saito, Postdoctoral Scholar (Jul. 2020-)
  • Kaoru Ohyama, Staff Scientist (Apr. 2021-)
  • Ai Takahashi, Technician (Apr. 2022-)

2. Students

  • Lorena Andreoli, Ph.D. student
  • Thato Mokhothu, Ph.D. student
  • David Bierbrauer, Ph.D. student
  • Tomoka Yoseyama, Research Intern
  • Miyu Nambu, Ph.D. student
  • Yu-Ju Lin, Ph.D. student
  • Josefine Reuschenbach, Ph.D. student (co-supervised with Izumi Fukunaga)
  • Reanna Norman, Research Intern
  • Yuma Kajihara, Ph.D. student (co-supervised with Kenji Doya)
  • Balashwethan Chockalingam, Ph.D. student (co-supervised with Tomoki Fukai)
  • Yuta Konno, Research Intern
  • Minato Abe, Research Intern

3. Collaborations

3.1 Inter-unit collaborations

  • Physiology underlying different spatial strategies (Wickens unit)
  • Hippocampal representation of social contingency (Froese unit)
  • Behavioral detection of the epileptic seizure (Uusisaari unit)
  • Synaptic plasticity under a specific state (Takahashi unit)
  • Effects of fine-controlled motor commands on hippocampal functions (Yoshida unit)
  • Role of Serotonin neurons in the paraventricular thalamus (Doya unit)
  • Olfactory working memory (Fukunaga unit)

3.2 Inter-institutional collaborations

  • Four collaboration projects are ongoing.

4. Publications

4.1 Journals

  1. Mokhothu TM*, Tanaka KZ* (co-corresponding authors). Characterizing Hippocampal Oscillatory Signatures Underlying Seizures in Temporal Lobe Epilepsy. Front. Behav. Neurosci., doi: 10.3389/fnbeh.2021.785328 (2021).
  2. Nambu MF+, Lin YJ+, Reuschenbach J+, Tanaka KZ (co-first authors). What does engram encode? – Heterogeneous memory engrams for different aspects of experience. Current Opinions in Neurobiology, (in press) (2022).

4.2 Books and other one-time publications

Nothing to report

4.3 Oral and Poster Presentations

  1. Tanaka KZ. "Tetrode recording of memory engram neurons in the hippocampus". Research Seminar at the neurosurgery lab in Ryukyu University, April 2021.
  2. Tanaka KZ. "Heterogeneous Memory Traces in the Hippocampus". Neuroscience Seminar at DANDRITE (Danish Research Institute of Translational Neuroscience), April 2021

5. Intellectual Property Rights and Other Specific Achievements

Nothing to report

6. Meetings and Events

6.1 Inclusive Mentoring mini-symposium

  • Date: February 16-17, 2022
  • Venue: Zoom
  • Speaker: Full list of speakers can be found here.

7. Community Services

7.1 Okinawa Science Mentoring Program 2021
Hiroto Ashitomi (Technical Staff), November 21-28 2021

7.2 OIST campus tour for Okinawan kids
Hiroto Ashitomi (Technical Staff), March 14 2022

7.3 Student Council
Lorena Andreoli (Ph.D. student, Chair), Thato Mokhothu (Ph.D. student)

7.4 OIST Peer Supporter Program
Lorena Andreoli (Ph.D. student), Thato Mokhothu (Ph.D. student)

7.5 Researcher Appreciation Month (RAM), 2021
Hiroto Ashitomi (Technical Staff) & Tomoka Yoseyama (Research Intern) (poster presentation)
Viviane Saito (Postdoctoral Scholar) (Lab tour, Tea time with STG associates, Invited seminars by external speakers, Trivia Night)

7.6 OIST Researcher Community (ORC)
Viviane Saito (Postdoctoral Scholar) (Advisory Board)

7.7 OIST Non-faculty Teaching Workgroup
Viviane Saito (Postdoctoral Scholar)

7.8 Junior Science and Humanities Symposium
Thato Mokhothu (Ph.D. student, guest judge)

7.9 OIST Neuroscience Club
Thato Mokhothu (Ph.D. student), Miyu Nambu (Ph.D. student), Yuma Kajihara (Ph.D. student), Kaz Tanaka (Assistant Professor)

7.10 OIST Gender, Equity, Diversity and Inclusion Committee (GEDI)
Lorena Andreoli (Ph.D. student), Kaz Tanaka (Assistant Professor)