The BRAIN simulator (BRAIN computer) 1972 Water S. Brainerd, MIT

In the TOC of the book Fundamental Programming Concepts by Water S. Brainerd and Jonathan L. Gross, I found a BRAIN computer/simulator. Probably named after Brainerd. Most is about BASIC. The book cover is also nice

chapter 9: machine language, assemblers and compilers
2. The BRAIN computer
3 BRAIN instructions
4 running a BRAIN program

(10.2. SNOBOL
appendix A: CALL 360-OS BASIC)
appendix C: the BRAIN simulator
Does anybody know this? Maybe it’s also described in other books? I only found Brain computer interfaces.

As it’s in the appendix, I assume it’s a theoretical/paper computer.

Also interesting: the programming language MOUSE (I also found as book)