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About my research
On the banks of the Seine in Paris stands the Institut du Monde Arabe, a research institute famous for its unique architectural design. The phrase above is attributed to Jean Nouvel, the architect who designed the building and adopted this idea as its guiding concept. I believe, however, that this idea is equally essential for the kind of research we do.
As scientists, we observe an enormous number of facts every day through experiments and computer simulations. Yet what we truly seek is not simply an ever-growing list of observations, but the ability to “see” the underlying principles behind those observations—the invisible truths that generate the data we measure.
To uncover these underlying truths, we formulate hypotheses, design and perform experiments, and analyze data. My own research focuses on biological phenomena—particularly information processing in the nervous system. Compared with engineered systems such as electronic devices, biological systems are extremely complex. Moreover, because they are the products of evolution, they may contain redundancies and historical contingencies that further complicate their organization. For this reason, it may be difficult to arrive at a genuine understanding of such systems through a strict division of labor—using only theoretical approaches such as computer simulations, or only experimental approaches—as is often done in contemporary physics.
In our group, we therefore combine experiment and theory in an integrated fashion to investigate the mechanisms of living systems, with a particular emphasis on neural information processing.
We hold regular seminars within the group. I hope that these seminars will serve as an opportunity to reflect on how best to approach and conceptualize biological phenomena. If you are interested in joining a seminar or simply visiting the laboratory, please feel free to contact me or any of the students who participate in these meetings.
What We Study
Neural systems use several different strategies to transmit information, but rapid communication is mediated primarily by brief changes in membrane potential known as action potentials. For example, when we ski or play tennis, the brain must compute how best to move the arms and legs. The commands resulting from these computations are conveyed to our muscles as sequences of action potentials.
As illustrated schematically in the figure below (the lower panel beneath the LSI diagram), individual action potentials all have essentially the same shape. Consequently, it is unlikely that information is encoded in the amplitude or width of single action potentials. This raises the question: which features of the action-potential sequence actually carry the information?
Several hypotheses have been proposed. One of the most widely discussed is the rate-coding hypothesis, in which information is represented by the firing rate—that is, by how frequently action potentials occur. Another is the temporal-coding hypothesis, in which information is carried by the precise timing of individual spikes. Despite extensive experimental and theoretical work, there is still no definitive consensus as to which of these coding schemes—or what combination of them—the nervous system primarily uses.
One of the central themes of our research is to address this question: how is information about the external world and motor commands represented and transmitted by patterns of action potentials in neural circuits?
Several squid species commonly caught in Japanese waters—namely the spear squid Heterololigo bleekeri (ヤリイカ), the swordtip squid Uroteuthis edulis (ケンサキイカ), and the bigfin reef squid Sepioteuthis lessoniana (アオリイカ)—possess large-diameter “giant axons” and an almost cylindrical body (mantle) shape. These features make them highly suitable for precise biophysical and electrophysiological measurements, and they have therefore been widely used as preparations for studying the electrical excitability of neurons.
Unfortunately, the fishing season for these species at any given port is relatively short, and this seasonality long constituted a major bottleneck for squid-based experiments. This situation changed when the late Dr. Gen Matsumoto established methods for long-term maintenance of spear squid (Heterololigo bleekeri) in captivity. Subsequent advances have further improved not only husbandry but also techniques for transporting live squid.
Contact information
Core Research Facility, Brain Science Lab.
Hokkaido University School of Medicine
West 7, North 15, Kita-ku,
Sapporo 060-8638, Japan
Phone: +81-11-706-4795