The Mysterious Reptile Brain

A web search of the words “reptile behavior” will likely show you a number of less-than-stimulating explanations. For example, Encarta Encyclopedia’s section on reptile behavior exclusively discusses the reptilian inability to thermoregulate (1). A search for “reptile brain” may bring up a common view that mammalian brains contain “layers of more sophisticated reasoning” over a reptilian foundation (2). Essentially, our lack of understanding has caused us to pigeonhole these creatures to a simplistic and inferior place in relation to mammals, but how valid and conclusive are our assumptions? What is our evidence?

A seemingly valid way to qualify our differences is to root them in the archaic evolutionary rift between “us and them.” However, as sound as this logic may seem, some research puts forth that there are long-preserved developmental patterns linking certain more “advanced” mammalian brain regions to reptilian counterparts (6). These patterns are evidenced in a fairly extensive series of experiments, involving trans-species (turtle-mouse) grafting; the results reveal heterospecific cell compatibility and a fundamental likeness in neuronal migration that implies organizational similarities.

I think it is safe to assert that complexity is a product of evolutionary development. If we can accept that the mammalian brain has been changing since its ancient split with the reptile brain, it would be impractical to assume that the reptilian brain has not also undergone substantial evolutionary modifications (5). It is unfortunate that our knowledge of this area is so greatly skewed toward the warm-blooded side of the story.

Another large portion of our lack of understanding stems from the stark rift between mammal and reptile behavior. It is my opinion that these behavioral differences provide much of the fuel for our deficient interpretation. But while it appears to us that reptiles barely respond to a great deal of environmental stimuli, such as sound, for example, they are physiologically perfectly capable of doing so: For example, while there is a lack of behavioral indications of this ability, the peak sensitivity for snake hearing is apparently superior to that of a cat (4). So, while we are unable to see more than just a little of their behavioral responses to stimuli, that is not reason enough to conclude that they lack the neurological complexity with which to process stimuli. Reactions exist - in forms that are not readily observable to humans. In fact, there is already some research indicating the possibility of low-frequency communication among chameleons (4). As the author, Melissa Kaplan, points out, it was not too long ago that a similar discovery was made regarding elephant communication. With a big idea like reptile communication on the table, it is impossible to rule out a fairly high level of complexity.

Reptiles are severely under-researched in general, and as such we cannot expect to have an ample understanding of the complexities of their minds. Even with much more exploration, however, our perceptual and evolutionary differences may render us ultimately unable to fully grasp reptilian reality. What’s definite is that until herpetological research has advanced a great deal further, conclusions about the level of reptile brain complexity simply cannot be drawn.

References

1) MSN Encarta’s page on reptiles (specifically the Reptile Behavior section) http://encarta.msn.com/encyclopedia_761579044_3/reptile.html

2) Reptilian Brain http://www.crystalinks.com/reptilianbrain.html

3) Reptile Brain Research, a ready-compiled list of relevant abstracts and papers. http://www.neurotransmitter.net/reptilebrain.html

4) Reptile Hearing – A Selection from Melissa Kaplan’s Herp Care Collection
http://www.anapsid.org/reptilehearing.html

5) The Evolutionary Origin of the Mammalian Isocortex http://cogprints.org/132/0/BBS12.html

6) Conserved Pattern of Tangential Neuronal Migration During Forebrain Development http://dev.biologists.org/cgi/content/full/134/15/2815#SEC2