How Many Brains Do You Have?

That's not really as silly a question as it sounds. Paleontologists long thought that some species of dinosaur had two brains, one in their head and one in their tail. Scientists now believe that the neural cavity in the tail was merely a place where many nerves exited the spinal canal, not a separate brain.

However, exciting new research into the human body shows that even the spinal cord has the capability to process information. The spinal cord has been long thought to simply be a connector between the computer-like brain and the many peripheral nerves of the body. But even under this simplistic model of the central nervous system, it becomes difficult to explain the "spinal arc reflex."

The spinal reflex is most easily explained by demonstrating the patellar reflex. When a doctor taps just below your knee, what he's really doing is quickly stretching your patellar tendon (the tendon that attaches your thigh muscles to your shin by way of the kneecap). Patellar tendon nerves send an "I've just been stretched" message to the spinal cord. The spinal cord responds with a lightning quick "Then you'd better tighten up again" message. The thigh muscles contract immediately, usually hard enough to cause a visible kick. This is the simplest form of spinal arc: message to the spine, instruction from the spine.

But even this simple arc proves that the spinal cord is more than just a connection from brain to limbs. It has functions and capabilities of its own.

According to Dr. Patrick Stroman of Canada's Queen's MRI Facility, ongoing research is proving that the spinal cord is more than just a relay station. While investigating the spinal cord's capacity for processing information, the researchers were astonished to find that more processing was accomplished by people who were alert. If the people were distracted, lethargic, or otherwise non-attentive, the spinal cord (as measured by MRI temperature changes) was much less active.

"The effect of attention is one of the reasons that when you're playing sports and you get hurt, you often don't become aware of the injury until after the game when your attention and focus changes," says Dr. Stroman. "We already knew that a person's level of attention affects information processing in the brain, but this finding has made us aware that level of attention has to be properly controlled in research that aims to accurately map spinal cord function."

So perhaps the dinosaur's "second brain" was, after all, more important that current paleontologists suggest. Although having an information-processing spinal cord isn't quite as nifty as having a second brain, daily new discoveries of the capabilities of the central nervous system continue to astonish.