I'm intrigued by (and want to write a story on) the social implications of research in neurology that is improving our understanding of the brain. I've seen studies that have done everything from used fMRI machines to identify the correlation of brain activity to thoughts of certain objects to sending brain signals across the world
I want to write a short story that is at least within the plausible penumbra of outcomes of the development of this technology. Sometime in the future, a combination of human ingenuity, technological development, vastly improved AI, and a lot of luck has resulted in an extraordinarily powerful brain-scanning technology—that can, slightly (but acceptably) implausibly, detect individual neurons firing— that can be (unethically) deployed covertly. My starting point is that the government covertly scans and observes a political opponent's surroundings and their internal brain activity over a period of six months, and all this time plugs the data of both the brain and the person's words and actions into a ridiculously powerful AI that machine "learns" the idiosyncratic correlations of that person's brain.
However, where I'm stuck, is figuring out the plausible limits of what this best possible brain scan and computer can figure out. In my story, I can justify that the AI figures out that the target is, for example, inappropriately secretly sexually aroused by something (good for blackmail), or is secretly worried or angry. But can any scanning technology make the leap from observing brain patterns to anything even close to what we would think of as "thought reading", as a telepath in a fantasy or superhero would? This is where my not being a neurologist hampers me: I don't understand to what extent my internal monologue is an empirically identifiable scientific state or a complete black box? I'd like to have the AI be able to use the correlations achieved by the suspect talking out loud to figure out when someone was thinking of particular words, but I am really not sure if being able to read someone's thoughts—even by use of technology—is just magic disguised as being on the edge of scientific plausibility.