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Brain Maps |
It turns out that we have a whole bunch of stuff mapped in our brains. There is a point to point map for the visual system, the auditory system, as well as maps for your motor and somatosensory system (the somatosensory system takes care of how you know where your different body parts are, and what they're doing at any one point in time). In fact there are many more maps in your brain, all working to interpret your internal and external experiences of the world.
 When we talk about brain maps the first name to drop is indeed the first person to map the brain, Wilder Penfield (now why couldn't my mom have named me something like Wilder, or something more dynamic than Gary). Dr. Penfield was a neurosurgeon at the Montreal Neurological Institute in the 1930's, and literally in search for a cure for chronic epilepsy. Armed with his electrodes and remnant of some Verizon commercial, Penfield would get into your head, again literally, and start poking around, asking "Did you feel that?". Patients would respond, "Yes doctor", stating they felt a tingling in their fingers, or ankle or elbow. Depending on where Penfield probed, their finger or foot would move slightly. It's not as bad as it all sounds, because the brain has no pain receptors, which is fortunate for Penfield, because this made it totally possible for him to record and map these different areas of the brain over the next 20 years. Two areas in particular, the motor cortex of the brains frontal lobe (controlling over 600 muscles), and the somatosensory cortex of the parietal lobe just behind it (see graphic below) were mapped. When the patient moved, Penfield knew he was on top of the motor area, and when they experienced touch, the somatosenory area.
 Well as you can imagine, Penfield at the end of all this had a pretty good map of our motor, and touch centers in the brain. This led to a depiction of the "Little Man" Penfield called a Homunculus. The area of the brain drapes down each hemisphere from the crown of your noggin, to just about the top of your ear. But this guy's parts are severely exaggerated, and not always where you might expect (see graphic). His thumb is up by the top of his head, and his genitals (not shown) are actually at the end of his toes. Wow, shades of foot fetishes! There is a book by Vilayanur S. Ramachandran MD, PhD entitled Phantoms in the Brain: Probing the Mysteries of the Human Mind. This story from one of Dr. Ramachandran's patients tells the story well. "Last year I had a terrible accident on my uncle's farm. I lost my left leg below the knee and I've had a phantom limb ever since. But I'm calling to thank you because your article made me understand what is going on." She cleared her throat. "Something really strange happened to me after the amputation that didn't make sense. Every time I have sex, I experience these strange sensations in my phantom foot. I didn't dare tell anybody because it's so weird. But when I saw your diagrams, that in the brain the foot is next to the genitals, it became instantly clear to me."
If there is a buzz word in neuroscience today I might guess it would be "PLASTICITY", the brain's ability to change and adapt over time. The above is a kind of encroachment example. With the actual foot being gone, neurons once dedicated to feeling this patient's foot were, if you will, taken over by the adjacent area of the parietal lobe dedicated to the patient's genitals.
What I am discussing above however is a small smattering of the multitude of maps in your brain. The wonder of it all is how they all come together to create your experience of the World and of your Self. To learn more I want to recommend a book entitled The Body Has a Mind of Its Own: How Body Maps in Your Brain Help You Do (Almost) Everything Better by Sandra and Matthew Blakeslee. |
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