My daughter asked me an interesting question the other day. She is 6, which puts her in that sweet spot where she yearns to know everything but still has a brain that is too young to grasp some of the more complicated topics. Being a huge fan of neuroscience and physiology, I try to answer her questions as accurately and honestly as I can without being inappropriate (yes, I do have a filter when it comes to the littles).
So back to her question. We were in the middle of talking about cells. She had been asking what a cell is shaped like, how brain cells talk back and forth with the body, etc. Then she asks:
"Is a cell alive?"
Immediately I say, "Yes, it's alive."
"Well," I say, "because it does things." (Yes, I know... You're thinking 'What kind of a second-rate, crappy answer is that?' But to be fair, I was driving and she's 6. I can hardly delve into cellular respiration or storing calcium in ion-gated organelles. Also, I wonder what it says about me that I assume an antagonistic role for my readers? Any psychologists out there care to comment? On second thought, I'd better leave that Pandora's Box and treasure trove of weirdness on the inside).
So anyway, I said that. And she of course can't leave it there because number one she never leaves anything anywhere until I say 'ok no more talking' or one of us falls asleep, and number two, she is smart enough to know that it was a second-rate, crappy answer.
"Well what about a TV," she says, "it also works." (shit)
"Yes, you're right, the TV works."
So right about now, I'm thinking about what a cell can do that a TV can't. A TV needs an external power source. Well, cells do, too. They depend on nutrients we consume. We all know a TV isn't alive, but why?
Well, it isn't sentient, it can't reproduce, it doesn't have machinery or genetic directions to divide, it cannot grow, mature, or age, etc. Tons of reasons. Cells, on the other hand each contain our entire genetic library. All within about a 10 micron- (or 1/100 mm) diameter. And they can re-create themselves. Great, I feel less stupid. Only slightly. But...
Then, all of this got me thinking. Not so much about what makes something alive, but what defines death. When can we consider a cell dead? As technology increases, the questions we are able to ask about the universe, the earth, and the human body grow more and more advanced. But we ride an asymptote and never really arrive at some answers. Our metrics and criteria for someone being alive have changed substantially over the years. Once upon a time, holding a mirror under a person's nose to check for the tell-tale fog of moist breath would give us our answer. No breath on the mirror? Dead. Then, we got more sophisticated and checked for heart beat. No thump thump sound? Dead. (I'm not a cold person, by the way, these are just facts). Now, of course, we know that you are not dead as soon as your heart stops beating. We can restart the heart's beating with specialized equipment. Now we have even more sophisticated machines - like functional MRI - that can read small electrical signals within the brain.
The really strange part to me is the interface between life and death. There is a small window of time between when a person is dead and when the body is dead. Yep, you heard me. And you probably have allll kinds of sassy questions for me. (It's the kind of readership I imagine. You're all just older versions of my daughter.)
-What is you anyway? Aren't you the same as your body?
-Even if they are separate, how can you be dead while you're body is alive?
Now, if you're like me, you can't ask that first question without laughing just a little bit. Or maybe that's just the writer in me chuckling at the subject verb disagreement. Anyway, these are fair questions. What makes you you is not really easy to answer. There are many ways to come at this topic and I don't intend to open up a religious or metaphysical dialogue at this juncture. I'll simply use consciousness as a proxy for you. When we die, all of our trillions of cells don't instantaneously poof out of existence or shut off. Yes, I said poof. Let's move past this moment. Our cells will slowly stop working because they no longer have access to oxygen and can no longer produce ATP, amongst several other things. Here's where the really creepy part comes in...
Ever read Stiff by Mary Roach? If not, I highly recommend. It discusses all different ways that bodies are used for research, etc., post-mortem. Things like ballistics, crime scene investigation practice, the list goes on and on. It's a fun read, which sounds weird to say, but the narrative voice makes it a really enjoyable book. I read it more than a decade ago and one part still stands out in my mind. She discusses how for a few seconds the brain is still alive after what we'd all consider a pretty final "he's dead" event like a beheading. Roach sites an example of a beheaded head turning his eyes towards a person who said his name. Talk about freaky! But it makes physiological sense. All of the sensory circuitry needed is still intact and alive after a beheading, likely for quite some time (your auditory and ocular nerves are all in perfect working order). Now, I'm willing to bet your brain loses consciousness out of shock long before it stops working. What is going on in that brain? Are you able to think?
Similarly, I've wondered about the 'brain in a vat' idea. In college I once called up my friend Maya, who was the smartest person I knew, and I asked her the following: If you were able to preserve a section of brain in a dish and fed it all the components it needed (oxygen, correct temp, nutrients, etc.), would it think? Even more specifically, if you stimulated one simple circuit, like a portion of the visual cortex- would it see? Maya just asked if I was high and left it there. I was not high.
Well, this blog post took a turn. Then another couple of turns. I don't know what the point of it was, but if you made it down here, you're definitely my kind of person. You're sassy, antagonistic, and don't mind talking about strange and morbid subjects. It's basically a trifecta.
Until next time!
Your average neuroscientist, Melinda