
One of the major obstacles in the research is that our brains are far more complex than any computer and aren't fully understood by scientists. Limited data can be currently analyzed using MRI machines, but we are far off from actually being able to transmit our thoughts via current technology. In Michio Kaku's Physics of the Impossible, he labels telepathy as a class I impossibility, meaning that it is "impossible today but does not violate the current laws of physics. So they might be possible in this century, or perhaps the next, in modified form."
Kaku, Michio, Physics of the Impossible. Anchor Books, NY 2008