Lobsters, Lasers, and Pain

As a means of preparing for the Infinite Summer, I spent a bit of last month reading some of David Foster Wallace’s nonfiction essays.  Perhaps my favorite of these is Consider the Lobster, well known for lending its title to a DFW compilation that I would recommend to all.  I find Infinite Summer’s brief on the piece to be both accurate and amusing:

It’s hard to know what Gourmet Magazine had in mind when they dispatched Wallace to the Maine Lobster Festival, but Consider the Lobster–an 8,000 words treatise (complete with footnotes) that grapples with the ethical quandary of boiling sentient creatures alive for the sake of culinary enjoyment–was probably not it.

As David Foster Wallace was a rather omnivorous thinker, the essay actually contains a serious discussion of the prevailing neuroscientific consensus on the question of whether lobsters are capable of experiencing pain:

Several irreproducible segues down the road from the PETA anecdotes, Dick—whose son-in-law happens to be a professional lobsterman and one of the Main Eating Tent’s regular suppliers—articulates what he and his family feel is the crucial mitigating factor in the whole morality-of-boiling-lobsters-alive issue: “There’s a part of the brain in people and animals that lets us feel pain, and lobsters’ brains don’t have this part.”

Besides the fact that it’s incorrect in about 11 different ways, the main reason Dick’s statement is interesting is that its thesis is more or less echoed by the Festival’s own pronouncement on lobsters and pain, which is part of a Test Your Lobster IQ quiz that appears in the 2003 MLF program courtesy of the Maine Lobster Promotion Council: “The nervous system of a lobster is very simple, and is in fact most similar to the nervous system of the grasshopper. It is decentralized with no brain. There is no cerebral cortex, which in humans is the area of the brain that gives the experience of pain.”

Though it sounds more sophisticated, a lot of the neurology in this latter claim is still either false or fuzzy. The human cerebral cortex is the brain-part that deals with higher faculties like reason, metaphysical self-awareness, language, etc. Pain reception is known to be part of a much older and more primitive system of nociceptors and prostaglandins that are managed by the brain stem and thalamus. On the other hand, it is true that the cerebral cortex is involved in what’s variously called suffering, distress, or the emotional experience of pain—i.e., experiencing painful stimuli as unpleasant, very unpleasant, unbearable, and so on.

I’m reasonably certain that constitutes the only time the word “nociceptor” has or will appear in the pages of Gourmet Magazine.  Of course, Consider the Lobster first appeared in 2004, and with the rapid pace of modern cognitive neuroscience, we’re starting to learn quite a bit more about exactly this question.  In fact, I was happy to see a highly relevant study arrive last month in The Journal of Neuroscience.

Michael C. Lee, Andre Mouraux, and Gian Domenico Iannetti at Cambridge and Oxford contributed a report on the relationship between patterns of electrical activity in the cerebral cortex and the conscious perception of a painful stimulus.  They used an infrared laser applied to the hands of brave (or well-compensated) subjects in closely-timed pairs.

When two sensory stimuli are placed close enough together, often only one will be perceived.  The thought is that the lower-level sensory information from the second stimulus cannot be processed if it arrives at the cortex before the higher-level representation (i.e. conscious percept) has subsided.  Because of this, the researchers were able to compare the electrical patterns associated with the perception of both stimuli against those when only one was reported.

The researchers considered three particular wave patterns: the N1, N2, and P2 potentials.  Of these, the N1 potential showed no relationship between wave magnitude and whether the subject reported sensing two discrete painful stimuli.  Both the N2 and P2 potentials, however, exhibited such a correspondence.

The authors argued that these patterns expose a dissociation in neural processing between nociception, or the the neural communication of a painful stimulus, and the conscious experience of pain.  The N1 wave, according to this model, is generated by lower relay processes, while the N2 and P2 potentials arise from whatever it is in the cortex that actually turns nociception into what it’s like to feel pain.¹

The electroencephalography used in this experiment lacks the spatial resolution of fMRI, so it is difficult to say exactly what structures or regions are involved in generating this activity.  The N2 and P2 waves, however, are strongest on top of and in the middle of the head, roughly where the primary and secondary somatosensory cortices are located.  The N1 wave, in contrast, is strongest on the side of the head opposite to the stimulated hand in the temporal region.  Not much can be gleaned from this, although it does correspond to the putative lower-higher division between the two classes of potentials.

What does this tell us about lobsters?  I suppose you would have to say it weighs on the “lobsters don’t experience” pain side of the scale, but it doesn’t fully tip it over.  After all, we have no idea, really, what happens to nociceptive stimuli when they’re processed by non-human animals or even those without a centralized nervous system.  There’s a strong case to be made that lobsters don’t experience pain in any way like we do, but that’s not to say that the way they experience pain isn’t nonetheless negative in some sense.  DFW makes a fairly compelling case that even a lobster acts in such a way as to express a preference, and that doing so reveals at least some level of pain perception.

I don’t think Consider the Lobster makes an open-and-shut case against eating the crustaceans, much less all meat, but I’m pretty sure David Foster Wallace wouldn’t have wanted it to.  If there is one thing about his writing (and let’s not kid ourselves, there are thousands of things about his writing), it’s a devotion to nuance and careful, serious thought.  The least we owe the animals that end up on our dinner plates is careful thought about their experience, or even the possibility thereof, and an attempt to make choices about food that properly value the contribution and sacrifice of another living being.

Lee, M., Mouraux, A., & Iannetti, G. (2009). Characterizing the Cortical Activity through Which Pain Emerges from Nociception Journal of Neuroscience, 29 (24), 7909-7916 DOI: 10.1523/JNEUROSCI.0014-09.2009

¹Anyone familiar with the philosophical debate about the nature of consciousness and the modern struggle with the mind-body problem has likely heard anti-physicalists follow Saul Kripke in attacking the identity theory that “C-fiber firing = pain.”  I’m pleased that this study seems to validate the argument I once made to Joe Levine, which is that modern neuroscience tells us that the true physicalist position involves much more than “C-fiber firing,” which is why it’s perfectly possible to imagine c-fibers firing without the corresponding experience of pain and that this rather banal fact tells us very little about the mind-body problem.  Here, c-fibers (and Aδ-fibers) fired without experience, because of the absence of N2 and P2 potentials.  Or, rather, because of the absence of the coordinated firing of the millions of intricately specialized neurons that contribute to those electrical potentials.  Which is to say that there is much we do not know about the brain, but we know enough to know not to revert to Cartesian myths.