Geoff Arnold's Blog

I know that I shouldn’t get hung up on terminology: these things are just arbitrary labels, aren’t they? Well, no – we can’t simply ignore the everyday meanings of words. So when Koch (and Block too) went on about the NCC, or neural correlate of consciousness during the symposium, it felt wrong. It was as if a biologist had been talking about the CCO, the chemical correlate of organisms, instead of cells. Yes, cells are made of chemicals, but no biologist would indulge in such a crude reductionism.
Talking about the neural correlates of consciousness sounds respectfully non-committal: after all, it just talks about correlation, nothing causal. But to my ears, there is certainly a strong implication of stable correlation, rather than (e.g.) a pattern that is stable at some higher level but is not bound to any specific neural elements. If such patterns exist, the minimal NCC would presumably encompass the entire collection of neurons which could potentially support them; this doesn’t sound like what Koch is getting at.
In general, I would prefer to adopt a more flexible systems-oriented language for the working of the mind, and explore the constraints and preferences that flow from the properties of the neural substratum. It is easier to capture the relationships between concepts at several levels of [evolutionary] design than it is to tease apart a single idea into multiple elements at different levels.
(In computing we call this refactoring: it’s hard enough at a single level, extraordinarily difficult when multiple levels are involved.)

Excellent symposium at Harvard Medical School this afternoon. A few observations follow. (Interesting how it’s easier to write about the positions with which you disagree, isn’t it?) And a nice bonus was finally getting to meet Bryan Bentz, a long-time fellow member of the Al Stewart mailing list.

• Dan Dennett (Tufts): Qualia, Unsplittable Atoms? If we want to go on using the term qualia, we have to give up the idea that they are ineffable and intrinsic. I drank that Kool-Aid a long time ago: no argument from me. A surprisingly direct rap at Block (citing his infamous jazz metaphor), and a nifty ju-jitsu move in response to Block’s attempt at a reductio in the Q&A. Thoroughly enjoyable.
• Patrick Haggard (UC London): Voluntary Action: Conscious Intention and Neural Activity: Updating Libet’s classic experiments on the Readiness Potential, which measured the curious fact that your brain starts preparing to act physically up to a second before you are conscious of deciding to act. Elegant experimental design has a distinctive aesthetics; this was a delightful talk. (I was reminded of one of my favourite books: The Existential Pleasures of Engineering by Florman.)
• Ned Block (BYU): Two Neural Correlates of Consciousness: Block proposes a distinction between phenomenal consciousness and access consciousness – roughly, the stuff that we’re aware of, and the subset that we can actually work with at the moment. This is a subtle distinction that some feel is either irrelevant (because in practice the categories coincide) or just plain wrong. My feeling is that Block overstretches when he tries to cite particular brain activation patterns as evidence of the distinction. (He also relies on Koch and Crick’s NCC concept – see below.) In addition, it seems to me (after insufficient thought, I’m sure) that accessibility crops up in other ways than this particular dichotomy: it feels more like a property of a mental event which captures one way in which it stands in relation to other events and functional systems of the mind. I’m not convinced by Block’s coupling of the idea to one aspect of consciousness, with a particular neurological implementation.
• Christof Koch (Caltech): Studying visual consciousness in humans using microelectrodes, magnets, and TV’s: I guess that Koch is the kind of hyperthyroidal character that you either love or loathe. He’s not my cup of tea at all. At the centre of his talk was a series of experiments in which the brain of an epileptic patient was wired up to explore the use of fine-grained electrical stimulation to control his seizures; a side benefit of this was that the same system could be used to detect the state of a few individual neurons. Koch showed the patient (and hence us) large numbers of faces, particularly those of celebrities; he found that certain pictures provoked neuronal activity. (In one case he found that the printed name of he person produced the same activity….) Rather than interpreting this data cautiously and skeptically, Koch started going on about “the Bill Clinton neuron” and the “Jennifer Aniston neuron”. I wish I’d been able to ask him to admit that his catchy phrase “the XXX neuron” really stands for “a random neuron which plays an unknown role in a larger neural structure [the NCC, or neural correlate of consciousness] which is activated in some way by XXX”. Even if it was a detector of some kind, it might play a functional role (“big nose”, “green eyes”, “sexy”) or indicate some correlation (“like Aunty Flo”, “seen on TV”). But Koch seems to be a true believer. In response to one question, he railed against “holistic” and “emergent” positions, or theories based on “patterns”. He espoused “specificity”, which for him seems to go down to the level of the single neuron. Unconvincing.