Where does consciousness come from? And when it ramps up or down, at what point does it move from consciousness to not-consciousness?
Carl Zimmer published both a blog post and a story in the New York Times yesterday looking at the work of Guilioi Tononi, a University of Wisconsin neuroscientist who looks at these questions. As Zimmer puts it, Tononi
has been obsessed since childhood with building a theory of consciousness–a theory that could let him measure the level of consciousness with a number, just as doctors measure temperature and blood pressure with numbers.
In short, Tononi is trying to develop a consciousness meter. This piqued my interest, as a few years ago, shortly after immersing myself in consciousness studies for a profile of Christof Koch, I wrote a piece for Slate pondering the implications of coming up with a conscious meter — or, as I called it, a “consciometer.”
Sometime in the next decade or so, neuroscientists will likely identify the specific neural networks and activity that generate the vague but vital thing we call consciousness. Delineating the infrastructure of awareness is biology’s most difficult problem, but a leading researcher like Christof Koch, Gerald Edelman, or Stanislas Dehaene could soon solve it. Science will then possess what might be called a “consciometer”—a set of tests (probably an advanced version of a brain scan or EEG) that can measure consciousness the way kidney or lung function is now measured.
The gist of the piece was that figuring this out might make some ethical dilemmas easier and some harder, because consciousness has taken on some distinct legal implications about both the end and the beginning of life.
The close association of consciousness with life dates only to the last half-century, when doctors learned to sustain heart and lung function long after awareness and will were gone. In the 1980s, legislators responded by establishing whole-brain death as the legal standard of death. At the same time, upper-brain death—the cessation of organized activity in the “thinking” cortex—became a common point at which to authorize the withdrawal of medical treatment. In theory, you can pick any state of health—upper-brain death or paralysis, for example—as your own signal to stop medical care. (Read an intensive-care doctor’s description of what happens when there’s no such signal.) But in practice most people choose the lack of demonstrable consciousness that doctors call a persistent vegetative state.
This practice spread through medicine and then law. And the basic equation — that is, measurable brain death = no consciousness = legally dead — was firmed up by the Schiavo case. This carries quite an irony, as conservatives, by pushing so hard on the Schiavo case, created a precedent that may bite them in beginning-of-life issues:
In the many appeals of the trial court’s decision to remove her feeding tube, however, state and federal courts repeatedly based their decisions on Schiavo’s cognitive status, making it the central issue in the case. Congress and the Bush administration similarly framed their efforts to restore Schiavo’s feeding tube. And here lies the affair’s great irony: Religious conservatives want the law to define life as the existence of a single living cell containing human DNA. Yet their Schiavo campaign bolstered both the acceptance of consciousness as the boundary between life and death and the authority of neuroscience to measure it.
The consciometer will strengthen this authority further.
The tricky part comes when these definitions of life get applied at the beginning of life. The landmark 1973 case Roe v. Wade replaced an old marker of life — the “quickening” or first movements of the fetus — with one based on fetal viability, which typically occurs at about the 23d week. This was a tactical move meant to provide a firmer marker for legal purposes. Law seeks clarity. Which is where a consciousness meter could be quite tempting to the courts — and discouraging to anti-abortion conservatives:
As leading neuroscientist Michael Gazzaniga, a member of President Bush’s Council on Bioethics, describes in his book The Ethical Brain, current neurology suggests that a fetus doesn’t possess enough neural structure to harbor consciousness until about 26 weeks, when it first seems to react to pain. Before that, the fetal neural structure is about as sophisticated as that of a sea slug and its EEG as flat and unorganized as that of someone brain-dead.
The consciometer may not put the abortion issue to rest—given the deeply held religious and moral views on all sides, it’s hard to imagine that anything could. But by adding a definitive neurophysiological marker to the historical and secular precedents allowing abortion in the first two-thirds of pregnancy, it may greatly buttress the status quo or even slightly push back the 23-week boundary.
There is another possibility. The implications of the consciometer could create a backlash that displaces science as the legal arbiter of when life ends and begins. Such a shift—a rejection of science not because it is vague but because it is exact—would be a strange development, running counter to the American legal tradition. Should a fundamentalist view of life trump rationalist legal philosophy? Roe v. Wade considered this question explicitly and answered no. For nonfundamentalists, that probably still seems right.
How will the sort of consciousness meter contemplated by Tononi affect this? At first glance it seems like it won’t or can’t apply: Tononi is using EEG sensors, and how would you get those onto a fetus? You wouldn’t. Yet if Tononi can generate acceptance of the idea that certain relative levels and types, or “shapes,”* of brain activity mark consciousness, then the only thing preventing the scoring of the consciousness level of fetuses is a way to measure their brain activity without going inside the uterus. And I suspect that can’t be long.
This is all very what-iffy, of course. One huge caveat: As we learn more about the states of consciousness in people in comas and such, we’re seeing more and more gradations or classes of consciousness (or lack thereof), rather than a firmer line between consciousness and brain death. It used to be you were “brain dead” or not. Now we’re finding gradations between. Work like Tononi’s might only break that down further, breaking a black-and-white on-off scale further into a spectrum with subtle gradations.
On the other hand, he and others — and common experience — suggests that we badly want to define something unique and vital and elemental about consciousness: To prove that there’s a certain level of awareness and meta-awareness that essentially defines what it is to be alive.
It’ll be interesting to watch this develop.
*I found Tononi’s notion of brain activity taking various shapes, explored in Zimmer’s blog post, the most intriguing part of the work Zimmer described. It brought immediately to mind (heh) György Buszaki’s beautiful and ground-breaking work on the vital role that patterns of brain-wave synchronization play in the brain’s work. (The first ten pages or so of Buszaki’s book are mind-blowing. Man’s on a roll.) So I was surprised when Zimmer’s story said, briefly and tantalizingly, that Tononi seemed to dismiss that work, or at least set it aside. I’d love to hear more about how his work differs or is incompatible. (Carl?)
John Hawks with a brief riff on Zimmer’s article; he ends up at Darwin, which is (Tononi > Zimmer > Hawks > Darwin) fitting enough.
My profile of Joseph LeDoux, whose work on the not-conscious workings of the brain suggests it’s rather vital to our essence as well.
Christof Koch’s fine series of columns in Scientific American Mind, where he keeps up with consciousness and other intriguing puzzles. He also has a nice book and an interesting web page.
The Tononi Lab.
Illustration by Robert Neubecker, courtesy Slate.com