Interviews with Imaging Experts - Yuji Ikegaya, Ph.D.

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Dr. Yuji Ikegaya is one of the world’s most productive neuroscience researchers. He investigates the plasticity of the brain and is an expert on neuronal circuit dynamics in the hippocampus. One major tool in his research is the CSU, which he uses to perform high-speed functional multineuronal calcium imaging (fMCI).

fMCI is an imaging technique that was developed by Yuste and Katz (Neuron 6:333-344, 1991). This technique involves the multicell loading of calcium fluorophores and has the unique advantages of being able to record hundreds of neurons over a wide area with single-cell resolution, identify the location of neurons, and detect non-active neurons during the observation period (http://gaya.jp/data/).

Why did you choose the CSU?

In my research, I need to record calcium reactions in brain slices at a high speed and with a wide field-of-view. That is why I was very interested in the high-speed image acquisition potential of the CSU. However, it was not until I joined Professor Rafael Yuste’s laboratory at Columbia University in 2002 that I had a chance to use the CSU. At first, they had only two-photon microscopes, but Professor Yuste agreed to buy a CSU system for my research.

CSU system

CSU system

What was your first impression of the CSU?

The first thing that really impressed me was that, in contrast to the single-point confocal microscope that I had used in Japan, there was significantly less photobleaching in the confocal imaging with the CSU. My colleagues at the Yuste laboratory knew only 2-photon microscopes and took this for granted, which would seem to suggest that the CSU and the two-photon microscopes had similar performance in this respect. In addition to the experimental conditions, I also developed software to analyze huge volumes of signal data.

fMCI

Spontaneous firing-induced somatic calcium spikes of CA3 pyramidal cells in a rat hippocampal slice culture

However, photobleaching at the focal point is actually much faster with two-photon imaging than it is with single-point confocal imaging, and thus, very significantly faster than with CSU imaging. For the fMCI experiments, stability during long-term and high-speed imaging is most critical; in this respect, fMCI is a very effective application that can make full use of the capabilities of the CSU.

What is the key to making full use of the CSU’s capabilities?

In general, progress in experimental research often speeds up following the arrival of an innovative new instrument.

Dr.Yuji Ikegaya

However, simply introducing a new instrument with new functions may not necessarily generate a breakthrough. I believe that we, the users of these new instruments, should thoroughly examine experimental conditions up to the point where we can know what each instrument’s limits are. Knowing these limits, we may then be able to devise a cutting edge experimental procedure that can lead to new discoveries. If you thoroughly examine every possible condition,you may discover that instrument’s unique characteristics and learn how to push it to its limits.

In the case of the CSU, I made a very thorough investigation of every experimental condition. Regarding hardware, selecting the right camera is essential for optimal CSU imaging. As for camera selection, those CSU users who think the CSU does not yield bright images are probably using old CCD cameras; I advise them to try new, highly sensitive EMCCD cameras. Of course, other hardware choices, most typically selection of the optimal objective lens, can impact imaging. Furthermore, the biggest challenge is to investigate the optimal sample preparation methods, for example, by determining how to make and culture brain slices and how to select fluorescent dyes and their loading conditions.

What are your plans for the future?

Dr.Yuji Ikegaya

While neuroscience experiments are typically limited to handling no more than 100 cells at a time with a maximum 50 Hz temporal resolution, our system allows the recording and analysis of more than 10,000 cells at up to 2,000 Hz.

By stretching the functions of the CSU system to the limit, we are able to acquire and analyze several orders of magnitude more data. I wish to continue my investigation of neuronal networks at the multi-cellular level, and this is only possible with the CSU. As our two CSU systems are running non-stop, I would acquire more if we could afford it.

Dr.Yuji Ikegaya


We were very pleased to see Dr. Ikegaya working hard to get the most out of the CSU by examining the widest possible range of experimental conditions, and believe that he has been quite successful in developing new approaches to elucidate neural networks. In addition, having learned of his kind concerns for certain dissatisfied CSU users, we are very motivated to advise them on how best to improve imaging by upgrading their old systems.

Aside from his top-tier research accomplishments, Dr. Ikegaya is famous as the author of many bestsellers, unfortunately all in Japanese. The majority of these are comprehensive commentaries on the latest neuroscience and brain function research. His sophisticated but easy-to-understand explanations fascinate even non-scientists and are drawing people young and old into wanting to learn more about the mysteries of the brain.


Yuji Ikegayaa Ph.D. http://www.gaya.jp/
Associate Professor in Graduate School of Pharmaceutical Sciences at the University of Tokyo


Interview date:  June 2009

Yuji Ikegaya, Ph.D.
Associate Professor in Graduate School of Pharmaceutical Sciences at the University of Tokyo
HP http://gaya.jp/

Biography

Mar, 1998 PhD in Graduate School of Pharmaceutical Sciences at the
University of Tokyo, Japan
Apr, 1998-
Jan, 2006
Research associate/Instructor in Graduate School of Pharmaceutical
Sciences at the University of Tokyo, Japan
Dec, 2002-
Mar, 2005
Postdoctral Research Scientist in Department of Biological Science
at Columbia University, USA
Oct, 2006- Researcher of PRESTO, Japan Science and Technology Agency
Aug, 2007- Assistant Professor in Graduate School of Pharmaceutical Sciences
at the University of Tokyo, Japan
Apr, 2008- Associate Professor in Graduate School of Pharmaceutical
Sciences at the University of Tokyo, Japan

Award list

2006
  • Konica Minolta Imaging Science Foundation, Young Investigator's Award
  • Japanese Pharmacological Society, Young Investigator's Award
  • Japan Neuroscience Society, Young Investigator's Award
2008
  • The Pharmaceutical Society of Japan Award for Young Scientists
  • The Commendation for Science and Technology by the Minister of Education,Culture, Sports, Science and Technology, The Young Scientists’ Prize

Main article list

  1. Yamada, R. X., Sasaki, T., Ichikawa, J., Koyama, R., Matsuki, N. and Ikegaya, Y. Long-range axonal calcium sweep induces axon retraction. J. Neurosci., 28:4613-4618, 2008.
  2. Sasaki,T., Matsuki, N., and Ikegaya, Y. Metastability of active CA3 networks. J. Neurosci., 27:517-528, 2007.
  3. Yamada, R. X., Matsuki, N. and Ikegaya, Y. cAMP differentially regulates axonal and dendritic development of dentate granule cells J. Biol. Chem., 280:38020-38028, 2005.
  4. Nakao, K., Matsuyama, K., Matsuki ,N. and Ikegaya, Y. Amygdala stimulation modulates hippocampal synaptic plasticity. Proc. Natl. Acad. Sci. U. S. A., 101:14270-14275, 2004.
  5. Koyama, R., Yamada, M. K., Fujisawa, S., Katoh-Semba, R., Matsuki, N., and Ikegaya, Y. Brain-derived neurotrophic factor induces hyperexcitable reentrant circuits in the dentate gyrus. J. Neurosci., 24:7215-7224, 2004.
  6. Ikegaya, Y., Aaron, G., Cossart, R., Aronov, D., Lampl, I., Ferster, D., and Yuste, R. Synfire chains and cortical songs: Temporal modules of cortical activity. Science, 304:559-564, 2004.
  7. Baba, A., Yasui, T., Fujisawa, S., Yamada, R. X., Yamada, M. K., Nishiyama, N., Matsuki, N. and Ikegaya, Y. Activity-evoked capacitative Ca2+ entry: Implications in synaptic plasticity. J. Neurosci., 23:7737-7741, 2003.
  8. Ikegaya, Y., Matsuura,S., Ueno,S., Baba,A., Yamada, M. K., Nishiyama,N. and Matsuki, N. βAmyloid enhances glial glutamate uptake activity and attenuates synaptic efficacy. J. Biol. Chem., 277:32180-32186, 2002.
  9. Ueno,S., Tsukamoto,M., Hirano,T., Kikuchi,K., Yamada, M.K., Nishiyama,N., Nagano, ., Matsuki,N. and Ikegaya, Y. Mossy fiber Zn2+ spillover modulates heterosynaptic N-methyl-D-aspartate receptor activity in hippocampal CA3 circuits. J. Cell Biol., 158:215-220, 2002.
  10. Ikegaya, Y., Kim,J.-A., Baba,M., Iwatsubo, T., Nishiyama, N. and Matsuki, N. Rapid and reversible changes in dendrite morphology and synaptic efficacy following NMDA receptor activation: Implication for a cellular defense against excitotoxicity. J. Cell Sci., 114:4083-4093, 2001.
  11. Mizuhashi, S. ,Nishiyama, N., Matsuki, N. and Ikegaya, Y. Cyclic nucleotide-mediated regulation of hippocampal mossy fiber development: a target-specific guidance. J. Neurosci., 21:6181-6194, 2001.
  12. Ikegaya, Y. Abnormal targeting of developing hippocampal mossy fibers following epileptiform activities via L-type Ca2+ channel activation in vitro. J. Neurosci., 19:802-812, 1999.

Creation date:  June 2009 

Related Products & Solutions

Life Science

Your microscope can be easily upgraded to confocal microscope with Confocal Scanner Unit. The multi-beam scanning method offers not only high-speed imaging but also significantly reduced photo-toxicity and photo bleaching because of very reduced laser power of each beamlet. The CSU series have been already delivered more than 2,000 units and supported leading-edge research around the world.

 

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