I'm trying to remember a novel I read in the late 1980s or early 1990s. Earth has been taken over by a robotic culture that has destroyed almost everything animal, vegetable, or human. A small number of humans survive like vermin in the corners, sneaking food, tools, and other supplies out of the factories. The different parts of the robotic culture are not completely unified into a single planetary mind. One faction has been experimenting with humans and has joined together some number (5? 8?) of humans at the temples. This "human starfish" can think as a single entity to some degree, and floats in a sort of amniotic tank in the robot's laboratory.
This sounds like Wolfbane, by Frederik Pohl and C M Kornbluth, first published in 1957 as a two-part serial in Galaxy.
The aliens were called Pyramids, because... well, that's what they looked like... IIRC, there was only one of them actually on Earth, on the summit of Mount Everest, which had been neatly trimmed to provide a horizontal base - this was illustrated on the magazine cover.
There wasn't just one starfish - there were hundreds or thousands of them, linked together to provide computing power. Humans were gathered for this purpose by force vortices that formed above anyone who happened to fall into a meditative trance. Eventually, the hero is gathered into one of the starfish, but manages to spread self-awareness and resistance throughout the network, resulting in the downfall of the Pyramids.
If this reminds you of The Matrix... me, too.