There is an axiom used in science that relates to this problem, which is that "the map is not the territory". What this means is that a map or model can never be as detailed as the thing it represents. That being the case, consider what would be entailed in mapping a person's entire brain. With 100 billion individual neurons, each having as many as ten thousand connections to other neurons, and each connection being able to express at least two states (i.e. on or off), it would require 2,000,000,000,000,000 (2 quadrillion) bits of data space on a computer to record all brain activity for a single moment of time.
But of course, this wouldn't do for any sort of mind-reading technology, because brain activity takes time before anything meaningful can be made of it. Neurons take as little as a millisecond (1/1000 of a second) to fire, so for an accurate reading we would want to be sure to take at least a thousand readings per second. And even one second won't reveal much, so for all practical purposes, let's say one hour is the minimum time allotment for reading one person's brain activity. There are 3,600 seconds in an hour, so we need 3,600,000 times more data space, or:
2,000,000,000,000,000 (neural connections)
x 3,600,000 (milliseconds per hour)
= 7,200,000,000,000,000,000,000 bits of data space for one hour for one person.
That's nearly 900,000 petabytes! (A petabyte is 1 million gigabytes.) This is comparable to the amount of data that gets transmitted over the internet in the equivalent amount of time. As you can imagine, this wouldn't be very practical at all, even if it were possible. This only accounts for the data space needed for storing the information, which says nothing about the active memory space that would be needed to work with it. It doesn't take into account long-term storage requirements for dictionaries of all the various signature frequency patterns and their meanings. It also doesn't take into account how this information would be interfaced by a human user. And remember, every person's brain is different, so each person would require a separate map and dictionary of signature patterns.
This should help to put things into proper perspective. As you can see, mapping the human brain at this level of precision is completely impractical in terms of data storage requirements, and after taking into account all the various problems I've explained elsewhere regarding remotely reading the brain's electromagnetic activity, this goes beyond just being impractical and becomes impossible.
There are other ways than brain mapping and remote electromagnetic influencing that are far easier to accomplish and less resource intensive to force a person to act, feel, or think outside of their own control. I've been researching this and the implementation is quite simple, really. It's based on hypnosis. With V2K technology, a hypnotic tone can be used to put a person into the appropriate state for hypnotic induction, after which the hypnotic suggestions/commands are inserted. Another method is to use the appropriate electromagnetic frequency (somewhere around 11 Hz) to induce the appropriate hypnotic state, which can be done even while the person is sleeping.
With V2K, subliminal audio messages can be directly inserted into the subconscious without the awake person being aware of it. If the person is being targeted while asleep, the messages don't necessarily have to be subliminal, but it would probably be safer for the attacker that they were.
Hypnosis allows suggestions or commands to be inserted that will be acted on later, when the person is no longer in a hypnotic state. The commands can be quite crafty, in that they can defeat any conscious attempts to override them or to even accept the possibility that the person has been hypnotized, thereby securing against discovery.
Hypnosis has also been shown to cause a telepathic connection between the hypnotist and the hypnotized subject, so that once it's established, suggestions can be given in this way. Another fact about hypnosis is that the more often the subject is hypnotized by the hypnotist, the easier the subject responds to him, and therefore the better the telepathic connection becomes.