Giant brain as world-controlling computer

[TomMazanec]

The computer is so powerful that it can recommend every book you would like, so you never miss a book or read one you don't like (among other things...this is what most impressed me). The surprise ending is when it is revealed that the "computer" is the brain of the inventor's wife, which he removed and placed in a tank enabling it to grow enormously.
Novelette (or long short story or short novella), probably Fifties.

 

[.matthew.]

I have no idea about what book that could be... but I really want that to be a real thing - basically the only reason to develop AI

 

[Foxbat]

Asimov wrote a few stories involving a giant computer called Multivac but I don’t recall it ever being revealed as a human brain so probably not the one you’re looking for.

 

[PaulMmn]

The Outer Limits episode The Brain of Colonel Barham involves a brain-in-a-tank:

The space race continues as the American military strives to be the first to successfully land a man on Mars. But the best candidate for the job, Col. Barham, is dying of an incurable ailment that has left him unable to walk. There is great debate whether a human being could survive a trip to Mars and whether a computer could adapt to unforeseen circumstances. It is decided to separate the Colonel's brain from his body and keep it alive, with neural implants connecting it to visual and audio input/output for the mission combining an astronaut's brain with a computer. But without a body, the brain becomes extremely powerful and develops megalomaniacal tendencies that endanger the life of his wife and others. [Wikipedia]