> It was only after they traced chemicals in the brain that they were able to verify that, indeed, the hippocampus was that squished, displaced object pushed toward the back of the brain.<p>Main takeaway (misleading title) is that this rat had a brain, but a region of fluid developed and pushed the brain towards the edges of the cranial cavity. The rat was still able to do most of the other basic tasks as the other rats, but may have suffered from anxiety.<p>And that's the extent of this article. I don't think we know how higher order functions were affected. I would guess that these (like what humans have) are not necessary to sustain life. A species can exist indefinitely as long as they can feed and reproduce faster than they die. These things are easy to do without higher order functions if food and reproductive mates are readily available.<p>I wouldn't be surprised if a lab rat without 99% of their brain didn't change much or could still complete basic tasks. I would be surprised if a human without 99% of their brain could function normally in society today, which requires relatively heavy higher order brain function.