The organizers Takashi Tominaga (Tokushima Bunri University) and Bernd Kuhn (OIST Graduate University) planned the symposium with the idea that a biophysical perspective is essential to understand how the brain works. The brain is an amazingly complicated and sophisticated information processing device, consisting of billions of neurons and thousands of billions of connections in the mammalian brain. To understand how the brain processes information, it is essential to readout and manipulate neuronal activity on all different temporal and spatial scales. We asked three pioneering biophysicists (Prof. Nemoto, Dr. Tani, and Dr. Nakamichi) who have invented various state-of-the-art biophysical methods, especially optical methods, to share their ideas. Also, the symposium picked up two distinguished topics selected from the submitted poster abstracts (Ms. Wen and Prof. Toyota). The symposium “Cutting-edge brain research from a biophysical perspective” was held at the 57th Biophysical Society of Japan Annual Meeting.
The session started with a talk by Prof. Bernd Kuhn and Dr. Christopher J. Roome (OIST Graduate University) entitled “Simultaneous spatio-temporal dendritic voltage/calcium mapping and somatic recording from Purkinje neurons in awake mice.” Prof. Kuhn introduced the basic mechanism of voltage sensing with synthetic voltage-sensitive dyes (VSDs) and, specifically, their previously developed and well-studied ANNINE (ANellated hemicyaNINE) dyes (Kuhn et al. 2004). The use of the electrochromic dye in combination with state-of-the-art two-photon microscopy techniques allows them to record the activity of a single Purkinje cell dendrite in awake mice (Roome and Kuhn 2018; Kuhn and Roome 2019).
Prof. Nemoto (Research Institute of Electronic Science, Hokkaido University; now National Institute for Physiological Sciences, Okazaki) presented the second talk entitled “Novel in vivo two-photon microscopy for vast and longtime neural activity.” Prof. Nemoto presented their novel developments on two-photon microscopy that allows deep brain imaging. Also, their improved high-power laser enables them to expand the spatio-temporal observation range (Goto et al. 2019). Prof. Nemoto also introduced a unique nano-sheet (Iijima et al. 2019) that allows researchers to observe in vivo brain activity.
Dr. Nakamichi and Dr. Tanifuji (Riken Center for Brain Science (CBS)) presented the talk “Functional optical coherence tomography with Fourier imaging reveals three-dimensional and micro-scale brain functional structure.” Their pioneering work on the application of optical coherence tomography to study functional anatomy of brain activity revealed a unique three-dimensional operational structure of a “pin-wheel.” Pin-wheels in visual cortex have been known for decades; however, no one knew their 3D structure. In this talk, a precise analysis of the pin-wheel structure and its physiological implications was presented (Nakamichi et al. 2018, 2019).
The following speaker was Dr. Tomomi Tani (Marine Biological Laboratory, Woods Hole; now The National Institute of Advanced Industrial Science and Technology (AIST), Japan). Dr. Tani started the talk entitled “Dissecting nano-scale architecture and dynamics of molecular assemblies in living cells with polarized light” with an introduction of their unique strategy to use polarized light. Using this technology allows them to detect the rotation of polarized light in real-time. Single-molecule resolution enables them to determine the molecular orientation in complex assemblies such as living systems (Mehta et al. 2016; Ishii and Tani 2019). Dr. Tani also uses polarized light to read out brain activity by intrinsic optical signals from hippocampal slices. This will allow to gain new biophysical insight into brain function (Koike-Tani et al. 2019).
The first of the distinguished poster topics was presented by the graduate student Ms. Jierong Wen (RMIT University). Ms. Wen talked about “(1Pos005) The role of C-terminal carboxylation in alpha-conotoxin LsIA interactions with human alpha7 nicotinic acetylcholine receptor in silico.” The alpha7 nicotinic acetylcholine receptor (alpha7 nAChR) is one of the critical target receptors relating to human psychiatric diseases such as Alzheimer’s types of dementia. Ms. Wen introduced a detailed analysis of the interaction of a possible cure (alpha-conotoxin LsIA) to alpha7 nAChR using advanced homology modeling and molecular dynamics (MD) simulations (Wen and Hung 2019).
Prof. Takashi Tominaga and Dr. Yoko Tominaga (Tokushima Bunri University) introduced wide-field VSD imaging of brain slice preparations in their talk “Optical view of the brain neural circuit activity: Voltage-sensitive dye (VSD) imaging.” Prof. Tominaga introduced the present state of VSD imaging with their fast imaging system. The talk showed how improved VSD imaging (Tominaga et al. 2018, 2019) allows researchers to observe plastic changes in the propagation of voltage signals in a wide brain area (Kajiwara et al. 2019).
The second distinguished poster topic was presented by Professor Masatugu Toyota (Saitama University and Univ. Wisconsin-Madison) entitled “(1Pos266) Long-distance Ca2+ transmission via glutamate receptor channel in plants.” Prof. Toyota studies how cells in plants communicate with each other using Ca2+ imaging. This results in fascinating movies. The talk highlighted the universal importance of membrane potential and Ca2+ signaling across all cells in tissue showing that even the study of phylogenetically remote systems can shed new light on the understanding of the brain (Toyota et al. 2018; Toyota 2019).
Overall, the symposium covered many cutting-edge technologies that have revealed and will reveal many novel aspects of brain function.
Footnotes
Publisher’s note
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Contributor Information
Takashi Tominaga, Email: tominagat@kph.bunri-u.ac.jp.
Bernd Kuhn, Email: bkuhn@oist.jp.
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