Once these scientists start playing with the mice's brains, they begin to mess with the natural order of things. They change the makeup of the mice's brains putting human matter into a mouse. Scientists should research human brains more before they alter the brains of others people and animals indefinitely.
If you inject human brain cells into an animal. You begin to play God and mess with the natural order of things. Though this may improve health in the future, I believe the scientist should do more research on the brain in other ways before messing with the brain of others.
Scientific discoveries are sometimes radical in their development. If we constantly set boundaries on what can and cant be done, we severely limit our ability as a species to progress, learn and move forward. A discovery such as this proves how powerful our minds are, and presents a plethora of future practical implications.