Symbolism, Imagery, Allegory
Putting brain implants in a patient is not a very subtle way to try to cure insanity. And it's also not a very subtle metaphor. In the world of Woman on the Edge of Time, people in power try to control their patients with implants, just like people in power try to control people in the real world with advertisements and propaganda.
Brain Implant Sadism
Even if brain implants are a rather clumsy, sci-fi way to say that the powers-that-be are after your brain, they are used to make some other, less obvious points. For instance, Alice's brain implant can make her want sex, and Connie notes that,
Now that Dr. Morgan had lost his fear of [Alice], there was something ugly in his demonstrations. (13.24)
The brain implants get wrapped up in sex and power, or power as sex—using them is a means not just of control, but of gaining sadistic pleasure. And that alludes to the fact that other forms of control (like Luis ordering his sister to cook and clean for him) can also include the same "something ugly."
Brain Implant Mess-Up
Another important point about the brain implants is that they don't actually work very well. The doctors can turn Alice on and off and manipulate her emotions, but when they try to make Skip attack, he just hurts himself. Oops.
Then when they operate on him, they don't end his suicidal impulses, but instead they "[teach] him the value of a quick clean death," so he finally ends up killing himself (14.120). Connie uses her future-training to completely mess up the implant, making the doctors confused and cranky: Dr. Redding "paced and muttered and Argent looked glum and edgy" (16.133).
The people in power in Woman on the Edge of Time, much like the powers-that-be in the real world, always think their control is complete and that they can make those on the bottom do anything. But the novel suggests that they're fooling themselves.
The brain implants control the brains of the implantors as much as those of the implantees. And while the implants certainly damage the patients, the implants also, at times, may turn around and hurt the doctors as well. (Especially if the doctors drink coffee.)