A Brief Guide to Being Shot in the Head – comments from across the pond

You know what this is about. I don’t have anything especially useful to say about the recent tragedy, or the question of crazy vs. political: at this stage, it’s all speculation. Let’s wait for the trial.
But anyway, the incredible thing is that Rep. Gabrielle Giffords survived a bullet to the head. How? 

One of the amazing things about the brain is that almost all of it is unnecessary. The bullet passed through Gifford’s left cerebral cortex, various parts of which are responsible for moving the right side of the body, seeing and hearing things from the right, and, in most people, language. But the only part of the brain which you actually need in order to live is the brainstem, which forms the top of the spinal cord.

The main reason you need your brainstem is that it controls breathing. It also controls your heart rate and blood pressure, but your heart pumps itself, without any input from the brain: the brain just does the fine tuning. Breathing, however, is controlled directly by several brainstem nuclei, and if you stop breathing, your blood will run out of oxygen and you’ll die (without artificial ventilation.)

Damage to any other part of the brain is survivable. Of course, you might just bleed to death from the head injury, or get an infection; there’s also the risk of brain swelling which can be fatal by compressing the brainstem (amongst other problems). This is why doctors have removed a large part of Gifford’s skull, to give the brain room.

But the brainstem can do a surprising amount on its own. In the early days of neuroscience, there was a bit of a fad for decerebrating animals, essentially removing everything except the brainstem. These animals were still “alive”, at least in the sense that they weren’t corpses; decerebrate cats can walk and run.

They don’t walk to anywhere, but this shows that the spinal cord and brainstem can control movement and respond to sensory feedback. It’s even on YouTube. The famous headless chicken that lived for over a year – that really happened, it’s no myth – is another such case.

 

Anonymous said…

That makes me wonder, at what point would you, as a neuroscientist, rate someone as dead. For example someone you know, how much of the brain would have to be gone in order to conclude that the actual person is deadand that there was no value in preserving its remaining body? 

I am also curious about memory (i.e. data loss). Do you believe there might be enough remaining in some cases that someone in coma might beresurrected in 20 years by either regrowing lost parts of the brain or replacing them with simulacra?

13 January 2011 17:01

 

Anonymous said…

Brain death is the absence of all brain stem reflexes. 

From Wikipedia: “The diagnosis of brain death needs to be rigorous, in order to be certain that the condition is irreversible. Legal criteria vary, but in general in the USA they require neurological examinations by two independent physicians. The exams must show complete absence of brain function (brain stem function in UK), and may include two isoelectric (flat-line) EEGs 24 hours apart (less in other countries where it is accepted that if the cause of the dysfunction is a clear physical trauma there is no need to wait that long to establish irreversibility). The widely-adopted Uniform Determination of Death Act in the United States attempts to standardize criteria. The patient should have a normal temperature and be free of drugs that can suppress brain activity if the diagnosis is to be made on EEG criteria.”

14 January 2011 15:03

 

Neuroskeptic said…

Anonymous: It’s a really good question. My answer is, I don’t know. I’m not sure the dichotomy of dead vs. alive really works when it comes to brain damage. 

I would consider a person who was reduced to a brainstem dead. But I wouldn’t consider an animal in the same situation dead. Because someone reduced to a brainstem, while biologically alive, has none of the attributes that make us human as opposed to animal.

But I’m not sure where to draw the line – metaphorically, or literally, I’m not sure where in the brain you’d have to cut to leave someone “alive” vs “dead”.

14 January 2011 19:53

 

Neuroskeptic said…

I wonder though. If my cat was reduced to her brainstem, I’d think, she’s dead. 

But if we were talking about a hypothetical generic cat in a lab, I’d think, it’s alive, just very stupid.

Which makes no logical sense, but that’s my intuition. Would be interesting to do an opinion/intuition poll of other neuroscientists…

14 January 2011 19:57

 

Chris said…

There’s an idea for a new blog post though. “Things I shouldn’t do, as a neuroscientist, but…” 

For example, as a psychologist I shouldn’t…
blame alcohol for disinhibiting my craving for a cigarette.

14 January 2011 22:04