Wednesday, January 03, 2007
Revelation (or, Why Surgeons Shouldn't Think)
Let's see if I can explain something I no longer understand. I'll preface by saying there are about three things I recall from studying neurosciences in med school. First, one neuroanatomist could draw perfect slices of the brain using both hands at once, holding more than one colored chalk in each. Second, studying I-don't-remember-what, a patient was presented who'd had a stroke which left him with a sort of aphasia. The professor held up some keys and asked the man what they were. The man said, "well, you know, you open doors...." "What's it called?" the professor asked. "It's, uh, it's what you use to start the car... It's..." Finally, after the same sort of back and forth, the prof tossed the keys to the man. As soon as he caught them, he said "Keys!" The story has no relevance to this post: it's just that it made an impression. It's the third vaguely remembered -- and no longer understood -- concept that I want to mention, because at the time it was a sort of metaphysical (and decidedly non-surgical) revelation.
Our brains, of course, are all about electricity: neurons connected in myriad ways to others, firing off little charges rolling down their axons and affecting whatever they're connected to in energetic little ways. (Making sense so far? It's the best I can do.) Simply put, what's involved is pumping ions across the membranes of the nerve cells, and maintaining different concentrations of those ions inside the cell, compared to the outside. When the permeability of the membrane is altered to allow a flow of ions across it, that flow is the firing of the nerve, resulting in the release of chemicals ("neurotransmitters") at the end of the nerve cell, which then affect the membrane permeability of those cells to which it's attached. So. You have zillions of interconnected cells, each having an influence on the membrane permeability of others, adding to or subtracting from it. Imagine holding hands with people on each side of you. And say that if your right hand is squeezed to a certain pressure, you'll yelp and squeeze your other partner with your left hand. Further imagine several people squeezing your right hand, and a few more massaging it to make it feel better. Getting to the point of yelping and squeezing your left amounts to the additive and subtractive sums of all those other people who are hanging on to your right. That, multiplied by a few trillion, is what's going on in our heads. Modifying cell membranes are all the sensations we own: our skin has a gazillion receptor nerves, responding to temperature, touch, moisture, etc. Our ears, eyes, noses are sending little packages of ion-flow altering messages to cells all over our brains, which are doing the same to others. At some level, all our thoughts and actions have correlations in electrical brain activity.
Oh wow, it occurred to me one day in a stuffy lecture hall: it's all connected. Everything going on in my brain is affected by everything going on around me. Were the room temperature different, the electrical milieu would be different. Likewise if the guy three people down weren't whispering to his neighbor, if there weren't a plane flying overhead, if someone was wearing different perfume, if the walls were red. What would I be thinking if the person in front of me had on a different shirt? And, of course, the ambient temperature is a result of the weather, the people in the room, the building -- what happened yesterday affects that as well. On and on it goes, to the proverbial butterfly beating its wings. Not to mention some person on the other side of the planet laughing or shooting a gun. The cosmic rays, the gravity of the sun. The book I read yesterday. George Washington sneezing in 1776. And, by golly, just imagine the warmth in which your brain would be bathing if you weren't reading this.