Have you ever seen the movie “Snakes On A Plane”? It might have occurred to you that, in real life, Burmese Pythons and Scarlet Kingsnakes don’t act like the computer-animated cobras from the film. Now imagine how a herpetologist would feel while watching it. I’m sensing some anger, some exasperation, maybe even a little righteous indignation.



Once the herpetologist works through these feelings, s/he might do an interview to capitalize on the movie’s popularity and correct some misconceptions the public has about snakes. Or, I don’t know, teach a class for non-science majors called “Snakes On The Colorado Plains”. Or write a blog post about it. That’s what I’m attempting to do here, but it’s not a movie from 2006 that’s got me thinking about reptiles. What happened was, I heard a RadioLab podcast which used the phrase “reptile brain”.

With one glance at this amazing animated gif that I found on VibeDoc.com, I am able to understand the reptilian brain.

As I’ll describe in more detail below, it’s not uncommon for neuroscience stories in the popular press to make reference to the “reptilian brain”. What does this term mean? Supposedly, it’s the most ancient part of the brain, which stuck around even as the rest of our brains evolved so we could be better than all other species. I hope my tone makes it obvious that I don’t think that’s the best description of brain evolution. I blame my righteous indignation on all the time I spent as an undergrad thinking about comparative neuroanatomy; comparative neuroscientists are very sensitive about the way people describe brain evolution. You might think the subject merits as much anger as improperly-placed apostrophes, but I hope I can convince you that that’s not the case.



The episode of RadioLab dealt with a neurodegenerative disease, frontotemporal dementia. As usual, the RadioLab team told a great story, and snuck in some interesting science at the same time. One of the hosts, Jad Abumrad, spoke with Bruce Miller, the neurologist who treated the patient described in the episode. Dr.Miller has clearly advanced treatment of neurogenerative diseases, and is an authority on frontotemporal dementia in particular (I like to research the important people that I write nasty blog posts about.) He pointed out that a “drive to repeat happens very early in the course of [the] illness”. Then he went on to outline his theory for why such obsessive-compulsive behaviors are associated with frontotemporal dementia. I don’t know for sure what Dr.Miller actually said, since Abumrad handled almost all the dumbing down of the multisyllabic science talk. Abumrad explained that, as the disease proceeds, neurons in the frontal lobes die, and they stop inhibiting other circuits in the brain. One of the areas thought to be modulated by frontal cortex is the basal ganglia, “this very ancient part of our brains” which Abumrad says you can call “our reptile brain”. If, as Miller said, the basal ganglia mainly execute “motor programs that we do repetitively every day”, then it would make sense that these repetitive actions increase as the frontal lobes stop modulating their activity.



It was at this point that Abumrad said that “birds and snakes get along with basically just this part of the brain”. As someone with a background in bird brains, I reacted to this comment by emitting the following noise: “Aarrrgh!”



Hey, dudes! A recent revolution in avian neuroanatomy [1] confirms that birds have just as much basal ganglia as we do—no more, no less. They don’t have as much neocortex—the wrinkly, layered neural tissue that we think makes us so smart—but there’s still plenty of brain sitting on top of the avian basal ganglia. And they can do plenty with all that extra brain. Comparative cognition has made a cottage industry out of showing that birds are in many ways just as smart, and in some ways smarter, than we are [2]. They use tools! They recognize themselves in mirrors (unlike your stupid cat)! They can differentiate individual grad students (unlike some professors)! And songbirds—which are perhaps the most successful group, evolutionarily speaking—learn their songs from tutors, much like we learn language from our parents. Let’s see your dog do that.

Please don’t think I’m attacking Bruce Miller and Jad Abumrad, though. What I am actually attacking is the Triune Brain Theory. When I hear someone use the phrase “reptilian brain”, I am almost positive that somewhere, somehow, the Triune Brain Theory got involved. It’s a great theory. Basically, it says that the human brain is just a snake brain, with a mouse brain on top of that, and then on top of all that, the magical new brain parts that make us human, and thus superior to all other species.

The Triune Brain Theory, as proposed by Paul MacLean