Yes it's concerning that such things exist, but I don't think it's as bad as it looks like. If you read the paper it clearly shows that they first showed the picture to the monkey, and then alalyzed how the brain responds.
This is like a high-tech version of the power analysis attack, when they know what to look for and then just search for it.
But the whole point of a password is that they don't know what to look for. If the password is random, then they can never guess it.
What is it like 5-10TB of memory that the brain can store? And then combine each piece of that data randomly, you almost have infinite number of combinations.
One thing I worry about is brain chips, make no mistake about it, those will be a huge problem. The guy in the article already wants police to use this technology to "catch criminals". I can't believe people are this stupid, this will be easily abused.