This report was written by Ms. Mengyuan Chen, Dr. Yi-Yuan Huang, Dr. Kanako Iwasaki, Dr. Masahiro Kiyota, Dr. Shota Murai, Dr. Masahito Nangaku, Dr. Nana Nishio, Ms. Atsuko Oba, Dr. Takeshi Sawada, Dr. Yusuke Takahashi, & Mr. Yoki Tatsumi

Overview

In August 2025, the IRCN team visited Boston, USA, engaging in a series of laboratory visits and a symposium that facilitated active international research exchange. Boston, with its blend of historical charm and cutting-edge innovation, provided an ideal environment for this international joint symposium. Walking through Harvard’s red-brick buildings and green courtyards, the team felt the vibrant intellectual energy that has long made the city a global center for the top level of science and education. This report summarizes insights gained from the lab visits and inspiring lectures that have led us to future research collaboration.

Laboratory Visits

A part of the team first visited Professor Hanspeter Pfister’s laboratory at Harvard SEAS, where the members observed a wide range of research projects in visual computing, including connectome visualization and augmented reality (AR)-based sports training systems. Experiencing the AR system firsthand provided a tangible sense of the potential for integration between neuroscience and engineering.

Then on a following day, all of our team toured the Lichtman Lab, a leading group in 3D electron microscopy-based connectomics research. The lab is notable for its innovative equipment development, which achieves both high efficiency and precision in sample preparation and imaging. At the Center for Brain Science, located in the same building, we observed facilities that support diverse research combining behavioral neuroscience and neuroimaging, including MRI scanners for both human and animal experiments and of course, Hensch Lab. In the afternoon, we visited Boston Children’s Hospital (BCH), an integrated pediatric research–clinical environment. Dr. Charles Nelson guided us through facilities, including high-density EEG, NIRS, and MRI, and we were impressed by the seamless system enabling patients to participate in research alongside clinical care. Following the tour, Dr. Charles Berde offered a lecture on their recent findings in collaboration with IRCN regarding general anesthesia affecting the developmental timing of visual processing.

Symposium

On the last day of our visit, the joint symposium took place in a lecture hall on the lower level of the Northwest Building at Harvard University. In the spacious foyer just outside the hall, a poster session was held by early-career researchers from both institutions, in which their lively discussions and spontaneous exchanges in this open area created a vibrant atmosphere and reflected the strong spirit of academic exchange and mutual curiosity. The talk session featured eight senior scientists from both Harvard University and the University of Tokyo, sharing their latest findings as follows.

Mustafa Sahin (Boston Children’s Hospital) presented research on neurogenetic disorders using tuberous sclerosis complex (TSC) as a model. He described how TSC1/2 mutations lead to cellular abnormalities such as altered neuronal size and increased cortical excitability, as well as autism-like behavioral symptoms. He also highlighted a potential use of the mTOR inhibitor rapamycin for early treatment. This presentation exemplified translational research connecting molecular mechanisms to behavioral outcomes, providing a model for IRCN’s future team science.
Yukiko Gotoh (UTokyo) reported her latest findings on the chromatin regulation of neuronal maturation. She provided evidence for a novel role of chromatin remodeling factors and histone modifications in stabilizing cell fate. She also demonstrated, including using functional ultrasound imaging, that neuron-specific knockout of an epigenetic regulator induces ASD-like phenotypes.
Paola Arlotta (Harvard SCRB) showed that long-term cultivation of human brain organoids can reproduce postnatal developmental processes and dynamic cell fate transitions. Mixing neural stem cells of different maturational ages revealed that older cells bypass early fates to generate late-born neurons, thereby broadening the potential of brain organoids as models of human brain development.
Takamitsu Watanabe (UTokyo) presented energy landscape analysis as a powerful method to study brain-state dynamics. He demonstrated distinct transition patterns in individuals with ASD and ADHD, and discussed real-time modulation of brain states via noninvasive stimulation. He also introduced applications of this method to aphasia research and comparisons of human and artificial language processing using large language models.
Haruo Kasai (UTokyo) introduced SYNCit, a novel synaptic chemogenetic approach, showing that synaptic plasticity not only supports long-term memory but also dynamically regulates cognition and arousal states. His work revealed circuit-level control of gamma activity and intermittent induction of behavioral arrest states.
Naoshige Uchida (Harvard MCB) described the neural basis of distributional reinforcement learning. He showed that D1 and D2 striatal neurons preferentially encode optimistic and pessimistic outcomes, and that dopaminergic neurons represent reward prediction errors across multiple timescales, providing new insights into decision-making under uncertainty.
Kiyoto Kasai (UTokyo) presented findings on adolescent brain development and environmental influences, summarizing over 20 years of psychosis research. Using the Tokyo Teen Cohort, his group revealed how factors such as bullying and urban living affect brain structure and psychopathology, and outlined future directions for translational psychiatry.
Catherine Dulac (Harvard MCB) reported on the relationship between inflammation and social behavior. She experimentally induced inflammation in ASD model mice by administering LPS to see whether their sociability would change. The results surprisingly showed that LPS-induced inflammation increased social huddling behavior in ASD model mice.

Conclusion and Future Directions

This visit and symposium together provided a valuable opportunity to reaffirm IRCN’s mission to advance our interdisciplinary Team Science approaches. Beyond the academic sessions, informal discussions over coffee and dinner in Harvard Square and along the Charles River deepened mutual understanding and sparked ideas for future projects. Moving forward, we plan to leverage the international networks established through this exchange to promote collaborative research and early-career researcher exchanges. Sharing the knowledge gained both within and beyond IRCN is expected to accelerate the development of next-generation neuroscience.

Acknowledgments

We sincerely thank Professors Hanspeter Pfister, Charles Nelson, Charles Berde, Mustafa Sahin, Paola Arlotta, Naoshige Uchida, and Catherine Dulac, as well as everyone from Harvard University and the Japan Society for the Promotion of Science, for their support in organizing and hosting this symposium.