Bayne and Howhy revisited

I first looked at ‘Global disorders of consciousness’, a paper by Tim Bayne and Jakob Hohwy, a pair with philosophy backgrounds, something over five years ago, not long after it first appeared. Something, I forget now what, prompted me to take another look, a second look which has proved more productive than the first – as much for what it provokes as for what it says.

At the margins

A paper about the consciousness (or not) of those in a persistent vegetative state (PVS), in a minimally conscious state (MCS), or in the throes of an epileptic fit, in particular in an absence seizure. Important in the first case as we do not usually want to turn off the life support for someone who is conscious. And temporary in the third case, with duration usually being in seconds and rarely being more than a few minutes. All important from a medical point of view given the numbers, with one estimate for the number of PVS cases in the US being 15,000 and for MCS cases there being 100,000 – although I have not traced the provenance of either of these numbers beyond reference 13. All important here because the nature of consciousness at the margins, on the boundaries, is likely to tell us something about consciousness in general – the boundaries of a phenomenon often being a good place to start looking. What is the relevant difference between inside and outside? What changes when you cross the fence?

Other natural  boundaries occur with trances and dreams. While hypnosis is an unnatural boundary which crops up below.

While at reference 4, the authors fiddled at another unnatural boundary of consciousness by looking at brain activity while gradually ramping up the level of the anaesthetic propofol in volunteer subjects. In the margins of which I also found at reference 5 that quite a lot of people were conscious after a fashion during propofol anaesthesia, but couldn’t remember about it afterwards. Reminding me of the link between consciousness and memory. From where I associate to the blanks that drinkers sometimes experience after excess.

Other boundaries include the sort of consciousness experienced by an animal – such as Nagel’s famous bat, to be found at reference 8, by someone with a profound mental handicap, perhaps without language, or by someone who is very young. And in connection with that bat, I might say I am still grappling with the phrase ‘there is something which it is like to be bat’ – neat though it might sound.

Absence seizures

The general idea used to be that subjects are absent during absence seizures, that is to say unconscious, but things turn out to be a bit more complicated than that. We are given a couple of examples of things being done during absence seizures that might be thought to involve consciousness.

First, a nineteenth century doctor who, in the course of  a seizure, examined a patient and wrote up his notes. After the seizure was over, he could remember nothing of the examination, but a second examination confirmed the results of the first.

Second, a twentieth century cyclist who, in the course of a seizure which started when he was cycling to work, turned around and cycled home. Again, after the seizure was over, he could remember nothing about turning around or about getting home.

I associate to the fairly common experience of ‘waking up’, as it were, while driving a car or riding a bicycle, with no memory of how one had got to where one had got to. Certainly both things happen to me from time to time.

Epileptic fits in general are by no means always unconscious and unremembered. However, the patients involved, unlike those in a PVS or a MCS, might be hard to catch in a scanner at the right time. An EEG headset seems (to this layman) a more likely alternative, assuming you could find enough volunteers to wear such a thing for protracted periods.

Describing consciousness

It has been good to be reminded that some people still attack consciousness directly, by asking their subjects what has been going on in their minds. Granted, there are all kinds of problems with this, not least that the subject needs to be in a position to supply such a report, they need, for example, to be able to hear and to talk, or at least to read and to write, but it is a salutary reminder of what it is that we are trying to unpick in neural terms.

Many workers like to think in two dimensional terms, with one dimension being the level of consciousness and the other being about the contents of consciousness. Where the level might reasonably be thought of as a number between zero and one, while contents is more ‘tick all the applicable boxes’, hopefully organised into some sensible order. 

We have, for example, the work of Pekala and others to develop a questionnaire used to elicit information about the experience of being hypnotised, ideally completed just as the subject emerges from that hypnosis, a small part of which is reproduced above from reference 2. Here, rather than ticking a box for present, we are given a six point (Likert) scale.

I associate to the work of Hurlburt and others on what they called Descriptive Experience Sampling, noticed at various places at reference 3. And to the thought that mainstream researchers into consciousness seem to prefer scanners to questionnaires.

Finding consciousness

We might hope one day to be able to define consciousness as something that can be measured in some way by putting the subject’s head inside a contraption, perhaps a scanner of some sort - rather in the way that one might define temperature by the height of the mercury in a standard thermometer - as opposed to defining it in thermodynamical terms, in terms of the activity of the atoms making up the thing with temperature. Various such definitions of consciousness have been proposed, but none have yet achieved consensus.

Nevertheless, computers can now distinguish the signals that come from a brain thinking about moving around a familiar space to those that come from a brain thinking about playing tennis. A distinction which can be made in some PVS subjects who have been instructed to think about one or the other.

Bayne and Hohwy give some space to examining the inference that some PVS subjects are conscious.

One form of inference is saying that thinking about anything in a sustained way is evidence of consciousness. Therefore some PVS subjects are conscious.

Another form is saying that thinking about A rather than B after oral instruction to that effect is evidence of intention. And intention is evidence of consciousness. Therefore some PVS subjects are conscious.

Both inferences are weakened by our lack of knowledge about the various ways in which a PVS brain might differ from a healthy brain. But I agree with them that the second of these two forms is evidence of consciousness. Evidence which should not be put aside in deciding what treatment, if any, is appropriate.

In which connection, I have been reminded of the attention given by the media in the first part of 2005 to Terri Schiavo, a PVS subject, shortly before her feeding tube was removed.

Other matters

I have been reminded of the concepts of reduction, agency and intention. All three of which have attracted much attention from philosophers. Plato, at reference 9, usually contains more than one wants to know about such things.

Conclusions

The paper comes to the uncontroversial conclusion that ‘global disorders of consciousness represent at once both one of the most challenging but also one of the most important areas of research in consciousness science’. 

While I conclude nothing in particular, beyond noting the demonstration that second reads can sometimes be very worthwhile.

References

Reference 1: Global disorders of consciousness - Tim Bayne and Jakob Hohwy – 2014.

Reference 2: The Phenomenology of Consciousness Inventory – Hypnotic Assessment Procedure (PCI-HAP): Administrator’s Manual – Ronald J. Pekala, V. K. Kumar, Ronald Maurer – 2009. 

Reference 3: https://psmv3.blogspot.com/search?q=descriptive+experience+hurlburt. 

Reference 4: Anterior insula regulates brain network transitions that gate conscious access - Zirui Huang, Vijay Tarnal, Phillip E. Vlisides, Ellen L. Janke, Amy M. McKinney, Paul Picton, George A. Mashour, Anthony G. Hudetz – 2021.

Reference 5: Incidence of connected consciousness after tracheal intubation – Sanders, R. D. et al. – 2017. 

Reference 6: https://en.wikipedia.org/wiki/Terri_Schiavo_case. 

Reference 7: https://www.epilepsy.org.uk/info/seizures-explained. 

Reference 8: What is it like to be a bat? - Thomas Nagel – 1974. 

Reference 9: https://plato.stanford.edu/. 

Reference 10: https://www.nhs.uk/conditions/epilepsy/. A place to start. 

Reference 11: https://en.wikipedia.org/wiki/Epilepsy. Rather heavier going.

Reference 12: https://cysticercosis.in/. I learn that epilepsy can result from infection with pork tapeworms, an unfortunately common problem in East Africa.

Reference 13: Raising consciousness - Joy Hirsch – 2005. Inter alia, a useful summary of the issues arising from the Terri Schiavo case.