They don't seem to mention if it is elective. An all or nothing mechanism might spell out words that the patient really didn't intend on others seeing (like "Ugh, that guy again! I can't stand the way he...")
It is pretty difficult to control your inner dialog against spontaneous and triggered thoughts.
Prediction: even if this requires surgery, unlocking inner thought will be used in criminal proceedings to establish guilt or attempt to be used to prove innocence. It will definitely be used unethically in military/intelligence interrogations until the law catches up.
I'm not sure if this would be able to detect the difference between truthful thoughts about actual memories, and intrusive thoughts that could give the entirely wrong impression.
Yet, they still do use lie detectors, even though the things they detect can be faked, or triggered out of personal alarm or offense. So it is entirely possible, regardless.
I have a PhD student working on EEG audio decoding. We are presently focused on a simpler subtopic: the detection of consonance and dissonance in the brain as it listens to music.
It is pretty difficult to control your inner dialog against spontaneous and triggered thoughts.
Yet, they still do use lie detectors, even though the things they detect can be faked, or triggered out of personal alarm or offense. So it is entirely possible, regardless.