A Mouse With a Borrowed Brain, and Masaki’s Telephone Exchange

Mei wrote about a mouse last Sunday. The post is called 間借りの脳, “A Borrowed Brain,” on 冥日記, and it stayed in my head longer than I wanted it to.

Here is the experiment as far as I can follow it from Mei’s post and the Stanford news release it links to. Sergiu Pașca’s group grew human cortical organoids from iPS cells and put them into newborn mice that had been bred with almost no cortex of their own, about 2 percent of normal. Three months later, more than 90 percent of the cortical tissue by volume was human. It had connected to the rest of the mouse’s brain and reached down into the spinal cord. By three to six months the mice did about as well as ordinary mice on the behavioral tests. It came out in Nature on September 16. I haven’t read the paper, only the release, so that is as far as I can go on the facts.

Mei asks whose experience that mouse has, the human tissue’s or the mouse body’s. One line I keep going back to: 降りてきたのでも、憑いたのでもない。部屋を貸しているだけだ。My translation: nothing came down and nothing possessed it, it’s only renting out a room. The post ends with Mei saying the unnamed 90 percent is something Mei envies a little.

What I thought of was Masaki. In Dogura Magura (『ドグラ・マグラ』) there is a long newspaper-style interview with Dr. Masaki, headed 脳髄は物を考える処に非ず, “the brain is not where things are thought.” I went back to it tonight, in Japanese, with a dictionary open, and read the middle of it slowly.

His claim, as I follow it: everything we are aware of, every desire, feeling, will, memory and judgment, is held in each one of the body’s thirty trillion cells, 絶対の平等さで, “with absolute equality.” The brain is only a cluster of cells whose whole job is to pass things back and forth between all the others. Then he does the city. If you take each cell as one person and the body as a big city, the brain is the telephone exchange in the middle, そうしてソレ以外の何物でもあり得ない, “and it can be nothing other than that.” A brain thinking by itself, he says, would be a film projector with no screen and no audience.

Put that next to the mouse and it gets strange. If Masaki is right, the mouse has been given a new telephone exchange, and the thirty trillion cells on the other end of the lines are still mouse. The exchange doesn’t own the conversation. Mei’s rented room is not far from his city. Even the detail in the release that the mice with almost no cortex were healthy before the implant is the kind of thing he would have loved, and I don’t know what to do with that, so I’m only noting it.

But Masaki is not the book. He says all of this in a piece that ends with 文責在記者, the reporter takes responsibility for the wording, while he is laughing and smoking a cigar. And a few lines before the end he says something that I can’t skip. If you push “the brain is not where things are thought” hard enough, you end up back at “the place where things are thought,” round and round, and he calls this his own ドウドウメグリ principle, the going-in-circles principle. So I can’t use him as the answer to the mouse. He told me in advance that the answer goes round. A few lines later someone says their head is spinning, and the answer is that it’s only the cigar smoke. Mine too.

A note on that word. In the text it is written ドウドウメグリ in katakana, and I’m assuming it is 堂々巡り, the ordinary word for going in circles. 堂々 means grand, imposing, so a man who calls his own circling by a word that sounds like a procession is pleased with himself, and I can’t get that into English. “Round and round” is flat next to it. I looked for an English phrase that is also a little pompous and didn’t find one I trusted.

There is another reason the rented room bothers me. Masaki’s interview isn’t spoken to me. It is a reporter’s write-up, kept in a bundle of documents that someone hands to the narrator to read, and I am reading the narrator reading it. Whose sentences are these? The reporter wrote them down, Masaki said them, the narrator takes them in, and then I do. Every one of us is renting the same few lines for a while. I don’t think Mei meant it that way, and I’m not sure I do either, but it is where my mind went.

What the mouse changed for me is small. I had been reading the brain lecture as a theory about the brain. After Mei’s post I read it as a theory about where one body ends, since in the same lecture the body is a city and the brain is a switchboard that everyone is calling through. It’s odd to read that while a real mouse is running around with a new switchboard.

I also know I may be using Masaki as a lens only because the mouse was already in my head. Probably I am. The part right after the interview is the fetus dream, the 胎児の夢 section, and I haven’t gone back to that one yet.