Donovan's Brain

Donovan's Brain (1953), directed by Felix E. Feist. Based on the 1942 science fiction novel of the same name, written by Curt Siodmak.

The story revolves around an attempt to keep alive the brain of millionaire megalomaniac W.H. Donovan after an otherwise fatal plane crash. Donovan, who has been pioneering the method of keeping the brain alive in electrically charged saline solution, becomes the first recipient of his treatment. Gradually, the increasingly evil brain develops telepathic abilities and becomes able to control the mind of Dr. Patrick Cory, the character who is keeping the brain alive.

The movie features Nancy Davis (better known as Nancy Reagan) as Janice Corey, wife of Dr. Patrick Corey. In an amazing find, Wikipedia links to the 1944 radio version with Orson Welles, available at archive.org (Orson Welles on Suspense). You can even download Welles' parody of Donovan's Brain!

You can also buy the book from Amazon.com, which presents this understated description (presumably from Pulpless, the publisher that reissued the book in 1999):

...Donovan's Brain is one of the most influential novels of our times.

Dr. Patrick Cory is a scientist who, unable to save the life of W.H. Donovan after a plane crash, keeps his brain alive through an illegal experiment.

The story provides an examination of human evil that is impossible to forget. W.H. Donovan is much more than one of the world's richest men. He is a megalomaniac even before Cory keeps his brain alive in the tank. Once freed of the distractions of the flesh, the will to power is all that drives the brain. It is able to communicate with Dr. Cory through telepathy, but that is only the beginning. Soon it begins to take over the scientist who keeps it alive. Possessed by the mind of Donovan, Cory finds himself helpless to fight the plans of the tycoon. Cory remains aware as he follows orders, becoming more and more like Donovan. His wife is helpless, his assistant is helpless, to stop Donovan's Brain!

A word of warning:Don't start reading this novel unless you have the time to finish it in one sitting! This is a true page turner.