Doctors at George Washington found by chance recently that stimulating a patient’s claustrum served to disrupt consciousness temporarily (abstract). The patient was being treated for epilepsy, and during this kind of surgery it is normal to use an electrode to stimulate areas of the brain in the target area before surgery to determine their role and help ensure the least possible damage is done to important functions. The claustrum is a sheet-like structure which seems to be well connected to many parts of the brain; Crick and Koch suggested it might be ‘the conductor of the orchestra’ of consciousness.
New Scientist reported this as the discovery of the ‘on/off’ switch for consciousness; but that really doesn’t seem to be the claustrum’s function: there’s no reason at the moment to suppose it is involved in falling asleep, or anaesthesia, or other kinds of unconsciousness, The on/off idea seems more like a relatively desperate attempt to explain the discovery in layman’s terms, reminiscent of the all-purpose generic tabloid newspaper technology report in Michael Frayn’s The Tin Men:
British scientists have developed a “magic box”, it was learned last night. The new wonder device was tested behind locked doors after years of research. Results were said to have exceeded expectations… …The device is switched on and off with a switch which works on the same principle as an ordinary domestic light switch…
Actually, one of the most interesting things about the finding is that the state the patient entered did not resemble sleep or any of those other states; she did not collapse or close her eyes, but instantly stopped reading and became unresponsive – although if she had been asked to perform a repetitive task before stimulation started, she would continue for a few seconds before tailing off. On some occasions she uttered a few incoherent syllables unprompted. This does sound more novel and potentially more interesting than a mere on/off switch. She was unable to report what the experience was like as she had no memory of it afterwards – that squares with the idea that consciousness was entirely absent during stimulation, though it’s fair to note that part of her hippocampus, which has an important role in memory formation, had already been removed.
Could Crick and Koch now be vindicated? It seems likely in part: the claustrum seems at least to have some important role – but it’s not absolutely clear that it is a co-ordinating one. One of the long-running problems for consciousness has been the binding problem: how the different sensory inputs, processed and delivered at different speeds, somehow come together into a smoothly co-ordinated experience. It could be that the claustrum helps with this, though some further explanation would be needed. As a long shot, it might even be that the claustrum is part of the ‘Global Workspace’ of the mind hypothesised by Bernard Baars, an idea that is still regularly invoked and quoted.
But we must be cautious. All we really know is that stimulating the claustrum disrupted consciousness. That does not mean consciousness happens in the claustrum. If you blow up a major road junction near a car factory, production may cease, but it doesn’t mean that the junction was where the cars were manufactured. Looking at it sceptically we might note that since the claustrum is well connected it might provide an effective way of zapping several important areas at once, and it might be the function of one or more of these other areas that is essential to sustaining consciousness.
However, it is surely noteworthy that a new way of being unconscious should have been discovered. It seems an unprecedentedly pure way, with a very narrow focus on high level activity, and that does suggest that we’re close to key functions. It is ethically impossible to put electrodes in anyone’s claustrum for mere research reasons, so the study cannot be directly replicated or followed up; but perhaps the advance of technology will provide another way.