北澤 茂 教授Kitazawa, Shigeru

Graduate School of Frontier Biosciences
Dynamic Brain Networks Lab, Graduate School of Frontier Biosciences

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Professor Kitazawa is working on neuron-level analysis of human behavior and mathematical modelling of his findings. Because the modelling demands sophisticated knowledge and techniques of statistical analysis, Professor Kitazawa hopes to develop an interdisciplinary approach.

A journey into the wonders of the human “eye”

My research is on human cognition of space and time. One of the many research questions I seek to answer is, “when we move our eyes, why does what we’re looking at still appear immobile?”

Human eyes move at an amazing speed. If a video camera moved at the same speed while filming, the footage would be blurred, but our eyes don’t have that problem at all. They must have some highly advanced mechanism for dealing with the movement. This mystery is touched on in texts from Arabia over 1,000 years ago, and in the work of the philosopher Descartes. My aim is to solve it through research that integrates a range of approaches including psychological experimentation and measurement of brain activity while watching moving images.


How long is “now”?

I also explore mysteries surrounding the perception of time, asking: what do we mean by “now”? In physical terms, “now” is not a linear concept, but it appears that our subjective perception of “now” is based on our brain’s synthesis of information gathered over a span between 0.1 and 0.2 seconds. A span of 0.1 seconds is almost identical to a single alpha brain wave cycle. My hypothesis is that alpha waves function as a kind of neural clock, bringing together information from fields as far as 20 centimeters away in 0.1-second units. The cerebral cortex contains around 15 billion cells, but each of these cells is only connected with around 1,000 others. In such a dispersed network, sharing information over a spread of 20 centimeters would certainly require some degree of laxity rather than exhaustive processing. I believe it may be possible to make sense of this capacity by investigating cases where we get the illusion that events are happening in reverse. I think this same principle of “laxity” may apply to the case of spatial cognition, enabling the objects we see to appear motionless while our eyes are moving.

Comfortable with a program centered on interdisciplinary research

photo_kitazawa02I already had some experience of working with researchers specializing in linguistics, so it was not especially difficult for me to fit in with the interdisciplinary focus of HWIP. In my research on cognition of time, too, I collaborate with researchers in such fields as linguistics and clinical neuropsychology. For example, temporal cognition is inextricably connected with language, as demonstrated by the way we use grammatical tenses. In psychology, too, the importance of temporal cognitive function is clear; think, for example, of the way that sufferers of cognitive disorders often lose the ability to identify today’s date.

It is my hope that HWIP facilitates interactions that generate new discoveries and insights. I look forward to encountering young talents capable of creating something truly novel.




北澤 茂 教授Kitazawa, Shigeru

Kitazawa, Shigeru

生命機能研究科 ダイナミックブレインネットワーク研究室

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一方、時間認識をめぐっては、人間にとっての「現在」とは何かについて研究を進めています。物理学的な「現在」には幅がないですが、私たちが心で感じる「現在」は、どうも0.1秒とか0.2秒程度の間の情報を脳が「総合」して作り出しているようです。0.1秒だとすれば、脳波のアルファ波の周期とほぼ同じです。このアルファ波が脳の時計のような役目をしていて、0.1秒ごとに最大で20 cmも離れた領域の間の情報を「総合」しているのではないか。大脳皮質には150億もの細胞がありますが、1つの脳細胞は1000ほどの細胞としかつながっていません。これほどまばらな結合で、0.1秒ごとに、20cmの距離を克服して情報を「総合」するにはかなりの「手抜き」が必要です。時間の順序判断が逆転するような錯覚の事例を調べると「手抜き」の仕方がわかると考えて研究を進めています。目を動かしても世界が動かないという空間認知にも、同じような「手抜き」の原理が使われていると思っています。