Brain tissue might be specialized fat, but I think about it like a bunch of muscles. Pretend for a second that the frontal lobes and executive function--the highly evolved stuffs--are like any other voluntary system. They’re self-directed lots of the time, but can be hijacked by the Fishbrain’s limbics and involuntary systems at any second. The higher functions get almost no input when this happens, and usually have no awareness of it either.