Researcher Information

MAJIMA Kei

Specially Appointed Associate Professor

Neural decoding: Reading thoughts from brain activity

Department of Biological Sciences, Behavioral Neurobiology

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Theme

Development of methods for neural decoding and their applications in neuroscience

FieldNeuroscience, Machine learninig, Quantum computation
KeywordNeural decoding, Brain decoding, Machine learning, AI, Multivariate analysis, Quantum computation, Quantum algorithm, Quantum machine learning, Combinatorial optimization, Quantum annealing, Black-box optimization, Vision, Sparse estimation, Bayesian estimation

Introduction of Research

My research focuses on "neural decoding technologies," which aim to read out perceptions, memories, and motor intentions from the brain. Specifically, I specialize in developing the software and statistical methodologies required for this decoding process. As an example, in 2024, we demonstrated that images imagined in the human mind can be reconstructed from brain signals measured by fMRI (Figure 1), although improving the reconstruction accuracy remains an ongoing goal. While my previous work has primarily involved humans, at Hokkaido University, I plan to collaborate with students and researchers at the Faculty of Science to expand the scope of my research to include animal models.

Through the development of these neural decoding methodologies, I am also integrating relatively new computational technologies that can accelerate computation, such as quantum computing, quantum-inspired algorithms, and quantum annealing. By leveraging these cutting-edge tools, I aim to achieve scalable processing of large-scale neural data (Figure 2).

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Figure 1: Overview of mental image reconstruction (Adapted from Koide-Majima, Nishimoto & Majima, Neural Networks, 2024).
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Figure 2: Computational time of quantum-inspired principal component analysis (Adapted from Koide-Majima & Majima, Neural Networks, 2021).

Representative Achievements

Mental image reconstruction from human brain activity: Neural decoding of mental imagery via deep neural network-based Bayesian estimation. Koide-Majima N, Nishimoto S, Majima K. Neural Networks. 2024.
Reconstructing visual illusory experiences from human brain activity. Cheng FL, Horikawa T, Majima K, Tanaka M, Abdelhack M, Aoki SC, Hirano J, Kamitani Y. Science Advances. 2023.
Deep image reconstruction from human brain activity. Shen G, Horikawa T, Majima K, Kamitani Y, PLOS Computational Biology. 2019.
Fast, accurate, and interpretable decoding of electrocorticographic signals using dynamic mode decomposition. Fukuma R, Majima K, Kawahara Y, Yamashita O, Shiraishi Y, Kishima H, Yanagisawa T. Communications Biology. 2024.
Quantum-inspired canonical correlation analysis for exponentially large dimensional data. Koide-Majima N, Majima K. Neural Networks. 2021.
Self Introduction

My primary affiliation is with the National Institutes for Quantum Science and Technology (QST), but I have also joined Hokkaido University under a cross-appointment to conduct research for the JST BOOST program. I’m still new to life in Hokkaido, and I am very much looking forward to working and researching in the beautiful natural surroundings of Hokkaido University.

Academic background2009 B.Sc., Faculty of Science, Kyoto University
2011 M.S., Graduate School of Information Science, Nara Institute of Science and Technology (NAIST)
2014 Ph.D., Graduate School of Information Science, Nara Institute of Science and Technology (NAIST)
2014 Researcher, ATR Computational Neuroscience Laboratories
2015 Assistant Professor, Graduate School of Informatics, Kyoto University
2020 Researcher, National Institutes for Quantum Science and Technology (QST)
2021 PRESTO Researcher, Japan Science and Technology Agency (JST)
2025- Senior Researcher, National Institutes for Quantum Science and Technology (QST)
2026- Specially Appointed Associate Professor, Faculty of Science, Hokkaido University
Affiliated academic societyJapanese Neural Network Society, Japan Neuroscience Society, Quantum Life Science Society
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