They start with the prefrontal cortex - first recording from (and often thereby destroying) the more advanced parts of the brain first. Once the monkey is too dumb to learn complex tasks, they move on to more posterior parts of the brain, like those responsible for object recognition. Finally, once the cortex is mostly destroyed, they start recording from the deeper regions that are usually hard to access. At some point the monkey will lose the ability to swallow its own saliva, or to control its nervous system, at which point they acquire more monkeys.

It is a dirty, ugly secret of neuroscience, and the potential benefits are questionable - we can often learn similar things from harming much less advanced species.

The left/right conflict story is so completely outdated that it is now inaccurate. I realize that was part of the image and not your addition, but they couldnt' have gotten that from any textbook written in the past 20 years.