From discovery of NIRS to that of COE

I had been searching ways to train my brain since I was 14, and in 1991 I found a principle to visualize brain function by illuminating brain response with near-infrared light with no harm.

This was the beginning of the NIRS (near-infrared spectroscopy) that is used worldwide.

This technique targets hemoglobin in the blood vessels. The hemoglobin carries oxygen. There are two types of hemoglobin, one that combines with oxygen and one that does not. One of the special features of this technique is to be able to measure quantity of increase or decrease of the hemoglobin at the measuring point.

Another feature is that it can be used for anybody - children, patients and healthy adults - with little pain under normal circumstances.

The birth of COE (cerebral mapping of oxygen exchange) study made it possible for us to discover facts we had never before known. With MRI brain analysis, COE can be used for effective education and rehabilitation.

Can brain function be extracted from the brain's blood stream?

After long research in the United States, I came to the conclusion that blood that was flowing itself could not be used for measuring brain function.

The brain's blood flow is a stream of blood cells. The problem is whether the flow carries information of brain functions.

Traditional NIRS had been detecting quantities of increase or decrease of blood flow that did not distinguish between flow in the veins or in capillary ateries..

Now there is much discussion about the brain on the news, but this is normally depending on the result of measured blood flow in the vein.

However, the vein only carries hemoglobin that has already given oxygen to neurons in the capillary.

So as far as the brain blood flow is used as an indicator for brain function, it is impossible to directly measure whether the site exactly worked.

My conclusion was that the response in the veins of the brain were a response outside of the brain and it could not be called as brain functional response (reference 1).

Then I focused on exchange of oxygen in the brain but not the brain blood flow, and successfully established an equation of oxygen exchange (reference 2).

This is the birth of COE.

COE captures oxygen exchange of hemoglobin in the capillary.

For example, it can distinguish between increased blood flow with deoxygenated hemoglobin due to brain activity, and increased blood flow with oxygenated hemoglobin due to inactivity of the brain.

Therefore, COE can tell us more accurately the brain works.

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