80 years before the invention of fMRI, which tracks blood flow in the brain to measure brain activity, this doctor describes a device for doing precisely that using x-rays. The headline suggests that it was already in use, but the article explains that it was still theoretical at the time.

He is now in correspondence with a scientist in Buenos Ayres who is constructing a device to be attached to the X ray apparatus by which the cells of the brain may be magnified at least 5,000 times. The new apparatus will consist of this magnifying instrument, of the Roentgen ray, more widely known as the X ray, and of the cinematograph. The X ray will disclose the action of the brain, the cinematograph will flash instantaneously each movement on a recording film, and the magnifying lens will give these such proportions as to make them visible to the naked eye…

“When you are thinking there is more blood in the cells of your brain than when your mind is inactive. All doctors know that the part of the body that is working is congested with blood.

“But not until the present has it been possible to study these cells at close range. Not till these new mechanical achievements has there been a way of determining what changes take place in the neurons.”

The doctor imagines that, once 500 or so test subjects have been properly studied, these tests could help determine whether or not a person is mentally fit or an imbecile. Perhaps science can even learn something about the soul. Okay, so maybe that use case is a little pseudoscience-y, but it’s still neat to see a germ of an idea that is actually used today.

X RAY MOVING PICTURE MACHINE SHOWS BRAIN AT WORK: Dr. Max Baff of Clark University Tells of the Remarkable Invention of a Scientist at Buenos Ayres Which May Pry Into the Soul’s Secrets. (PDF)

From September 4, 1910