This editorial piece notes that we still haven’t nailed down the neural correlates of consciousness (NCCs). It’s part of a Research Topic collection on the subject, and it mentions three candidates featured in the papers which have been well-favoured but now – arguably at any rate – seem to have been found wanting. This old but still useful paper by David Chalmers lists several more of the old contenders. Though naturally a little downbeat, the editorial piece addresses some of the problems and recommends a fresh assault. However, if we haven’t succeeded after twenty-five or thirty years of trying, perhaps common sense suggests that there might be something fundamentally wrong with the project?
There must be neural correlates of consciousness, though, mustn’t there? Unless we’re dualists, and perhaps even if we are, it seems hard to imagine that mental events are not matched by events in the brain. We have by now a wealth of evidence that stimulating parts of the brain can generate conscious experiences artificially, and we’ve always known that damage to the brain damages the mind; sometimes in exquisitely particular ways. So what could be wrong with the basic premise that there are neural correlates of consciousness?
First, consciousness could itself be a mixed bag of different things, not one consistent phenomenon. Conscious states, after all, include such things as being visually aware of a red light; rehearsing a speech mentally; meditating; and waiting for the starting pistol. These things are different in themselves and it’s not particularly likely that their neuronal counterparts will resemble each other.
Then it could be realised in multiple ways. Even if we confine ourselves to one kind of consciousness, there’s no guarantee that the brain always does it the same way. If we assume for the sake of argument that consciousness arises from a neuronal function, then perhaps several different processes will do, just as a bucket, a hose, a fountain and a sewer all serve the function of moving water.
Third, it could well be that consciousness arises, not from any property of the neurons doing the thinking, but from the context they do it in. If the higher order theorists were right, to take one example, for a set of neurons to be conscious would require that another set of neurons was directed at them – so that there was a thought about the thought But whether another set of neurons is executing a function about our first set of neurons is not an observable property of the first set of neurons. As another example it might be that theories of embodiment are true in a strong sense, implying that consciousness depends on context external to the brain altogether.
Fourth, consciousness might depend on finely detailed properties that require very complex decoding. Suppose we have a library and we want to find out which books in it mention libraries; we have to read them to find out. In a somewhat similar way we might have to read the neurons in our brain in detail to find out whether they were supporting consciousness.
Quite apart from these problems of principle, of course, we might reasonably have some reservations about the technology. Even the best scanners have their limitations, typically showing us proxies for the general level of activity in a broad area rather than pinpointing the activity of particular neurons; and it isn’t feasible or ethical to fill a subject’s brain with electrodes. With the equipment we had twenty-five years ago, it was staggeringly ambitious to think we could crack the problem, but even now we might not really be ready.
All that suggests that the whole idea of Neural Correlates of Consciousness is framed in a way which makes it unpromising or completely misconceived. And yet… understanding consciousness, for most people, is really a matter of building a bridge between the physical and the mental; even if we’re not out to reduce the mental to the physical, we want to see, as it were, diplomatic relations established between the two. How could that bridge ever be built without some work on the physical side, and how could that work not be, in part at least, about tracking neuronal activity? If we’re not going to succumb to mystery or magic, we just have to keep looking, don’t we?
I think there are probably two morals to be drawn. The first is that while we have to keep looking for neural correlates of consciousness in some sense (even if we don’t describe the porject that way), it was probably always a little naive to look for the correlates, the single simple things that would infallibly diagnose the presence of consciousness. It was always a bit unlikely, at any rate, that something as simple as oscillating together at 40 Hertz just was consciousness; surely it’s was always going to be a lot more complicated than that?
Second, we probably do need a bit more of a theory, or at least a hypothesis. There’s no need to be unduly narrow-minded about our scientific method; sometimes even random exploration can lead to significant insights just as well as carefully constructed testing of well-defined hypotheses. But the neuronal activity of the brain is often, and quite rightly, described as the most complex phenomenon in the known universe. Without any theoretical insight into how we think neuronal activity might be giving rise to consciousness, we really don’t have much chance of seeing what we’re after unless it just happens by great good fortune to be blindingly obvious. Just having a bit of a look to see if we can spot things that reliably occur when consciousness is present is probably underestimating the task. Indeed, that is sort of the theme of the collection; Beyond the Simple Contrastive Approach. To put it crudely, if you’re looking for something, it helps to have an idea of what the thing you’re looking for looks like.
In another 25 or 30 years, will we still be looking? Or will we have given up in despair? Nil Desperandum!