What psychedelic research can, and cannot, tell us about consciousness

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The short piece below first appeared in Scientific American (Observations) on October 26, 2018.  It is a coauthored piece, led by me with contributions from Michael Schartner, Enzo Tagliazucchi, Suresh Muthukumaraswamy, Robin Carhart-Harris, and Adam Barrett.  Since its appearance, both Dr. Kastrup and Prof. Kelly have responded. I attach links to their replies after our article, offering a few comments in further response (entirely my own point of view). These comments just offer additional clarifications – I stand fully by everything said in our Sci Am piece.

It’s not easy to strike the right balance when taking new scientific findings to a wider audience. In a recent opinion piece, Bernardo Kastrup and Edward F. Kelly point out that media reporting can fuel misleading interpretations through oversimplification, sometimes abetted by the scientists themselves. Media misinterpretations can be particularly contagious for research areas likely to pique public interest—such as the exciting new investigations of the brain basis of altered conscious experience induced by psychedelic drugs.

Unfortunately, Kastrup and Kelly fall foul of their own critique by misconstruing and oversimplifying the details of the studies they discuss. This leads them towards an anti-materialistic view of consciousness that has nothing to do with the details of the experimental studies—ours or others.

Take, for example, their discussion of our recent study reporting increased neuronal “signal diversity” in the psychedelic state. In this study, we used “Lempel-Ziv” complexity—a standard algorithm used to compress data files—to measure the diversity of brain signals recorded using magnetoencephalography (MEG). Diversity in this sense is related to, though not entirely equivalent to, “randomness.” The data showed widespread increased neuronal signal diversity for three different psychedelics (LSD, psilocybin and ketamine), when compared to a placebo baseline. This was a striking result since previous studies using this measure had only reported reductions in signal diversity, in global states generally thought to mark “decreases” in consciousness, such as (non-REM) sleep and anesthesia.

Media reporting of this finding led to headlines such as “First evidence found that LSD produces ‘higher’ levels of consciousness” (The Independent, April 19, 2017)—playing on an ambiguity between cultural and scientific interpretations of “higher”—and generating just the kind of confusion that Kastrup and Kelly rightly identify as unhelpful.

Unfortunately, Kastrup and Kelly then depart from the details in misleading ways. They suggest that the changes in signal diversity we found are “small,” when it is not magnitude but statistical significance and effect size that matters. Moreover, even small changes to brain dynamics can have large effects on consciousness. And when they compare the changes reported in psychedelic states with those found in sleep and anesthesia, they neglect the important fact that these analyses were conducted on different data types (intracranial data and scalp-level EEG respectively—compared to source-localized MEG for the psychedelic data)—making quantitative comparisons very difficult.

Having set up the notion that the changes we observed were “small,” they then say, “To suggest that brain activity randomness explains psychedelic experiences seems inconsistent with the fact that these experiences can be highly structured and meaningful.” However, neither we nor others claim that “brain activity randomness” explains psychedelic experiences. Our finding of increased signal diversity is part of a larger mission to account for aspects of conscious experience in terms of physiological processes. In our view, higher signal diversity indicates a larger repertoire of physical brain states that very plausibly underpin specific aspects of psychedelic experience, such as a blending of the senses, dissolution of the “ego,” and hyper-animated imagination. As standard functional networks dissolve and reorganize, so too might our perceptual structuring of the world and self.

“In short, a formidable chasm still yawns between the extraordinary richness of psychedelic experiences and the modest alterations in brain activity patterns so far observed.” Here, their misrepresentations are again exposed. To call the alterations modest is to misread the statistics. To claim a “formidable chasm” is to misunderstand the incremental nature of consciousness research (and experimental research generally), to sideline the constraints and subtleties of the relevant analyses and to ignore the insights into psychedelic experience that such analyses provide.

Kastrup and Kelly’s final move is to take this presumed chasm as motivation for questioning “materialist” views, held by most neuroscientists, according to which conscious experiences —and mental states in general—are underpinned by brain states. Our study, like all other studies that explore relations between experiential states and brain states (whether about psychedelics or not), is entirely irrelevant to this metaphysical question.

These are not the only inaccuracies in the piece that deserve redress. For example, their suggestion that decreased “brain activity” is one of the more reliable findings of psychedelic research is incorrect. Aside from the well-known stimulatory effects of psychedelics on the excitatory glutamate system, early reports of decreased brain blood flow under psilocybin have not been well replicated: a subsequent study by the same team using a different protocol and drug kinetics (intravenous LSD) found only modest increases in brain blood flow confined to the visual cortex. In contrast, more informative dynamic measures have revealed more consistent findings, with network disintegration, increases in global connectivity and increased signal diversity/entropy appearing to be particularly reliable outcomes, replicated across studies and study teams.

Consciousness science remains a fragile business, poised precariously between grand ambition, conflicting philosophical worldviews, immediate personal relevance and the messy reality of empirical research. Psychedelic research in particular has its own awkward cultural and historical baggage. Against this background, it’s important to take empirical advances for what they are: yardsticks of iterative, self-correcting progress.

This research is providing a unique window onto mappings between mechanism and phenomenology, but we are just beginning to scratch the surface. At the same time—and perhaps more importantly—psychedelic research is demonstrating an exciting potential for clinical use, for example in alleviating depression, though larger and more rigorous studies are needed to confirm and contextualize the promising early findings.

Kastrup and Kelly are right to guard against overplaying empirical findings by the media. But by misrepresenting the explanatory reach of our findings in order to motivate metaphysical discussions irrelevant to our study, they risk undermining the hard-won legitimacy of a neuroscience of consciousness. Empirical consciousness science, based firmly on materialistic assumptions, is doing just fine. And unlike alternative perspectives that place themselves “beyond physicalism,” it will continue to shed light on one of our deepest mysteries through rigorous application of the scientific method.

You can read Dr. Kastrup’s response here, and Prof. Kelly’s here. In the spirit of constructive clarification I will offer a few additional comments on the parts of the work I was involved in: the signal diversity study and the general interpretation of how empirical work on the brain basis of psychedelic research speaks to metaphysical debates about the nature of consciousness. These comments relate mainly to Prof. Kelly’s critique.

(With respect to Dr. Kastrup’s comments I will simply offer, as he no doubt knows, that relating fMRI BOLD to neural activity, in terms of global baseline and regionally differentiated metabolics, functional neuronal connectivity, and so on – remains an area of extremely active research and rapid methodological innovation.)

1. Prof Kelly notes that we do not provide ‘exact N’s for the data segments we used to compute measures of signal diversity.  This is because they varied substantially between drug condition, participant, and analysis method. We do however clearly state that “[a]nalyses were performed using non-overlapping segments of length 2 sec for a total length between 2 min and 10 min of MEG recording per participant and state” (Schartner et al 2017, p.5)” These numbers indeed lead to a total number of segments ranging from ~3,500 to ~27,000 per participant and per state (since we have 90 channels/sources per segment). These large numbers provide stable statistical inference (e.g., by the central limit theorem). Also, as we mentioned (above) the absolute scores on the diversity scale are not as meaningful as effect size and statistical significance. I’d also like to add that in our paper we go to great lengths to establish that our reported diversity changes do not trivially follow from well-known spectral changes in the drug conditions – this is part of the unavoidable computational sophistication of the method, when done properly.

2. When Prof. Kelly says that “relatively simple neuroimaging methods can easily distinguish between wakeful and drowsy states and other commonplace conditions” I do not disagree at all. Our paper was specifically interested in signal diversity as a metric of brain dynamics (and as mentioned above we take care to de-confound our diversity results from spectral changes). Also, we do not claim these diversity changes fully explain the extraordinary phenomenology of psychedelic states. However, I do believe that they contribute helpfully to the incremental empirical project of mapping, in explanatorily satisfying ways, between mechanism and phenomenology.  I defend the general approach in this 2016 Aeon article: ‘the “real” problem of consciousness’.

3.  I also agree the measures of signal diversity we apply are only part of the story when mapping between experiential richness and brain dynamics. My lab (and others too) have have worked hard on developing empirically adequate measures of ‘neural complexity’, ‘causal density’, and ‘integrated information’ which are theoretically richer – but unfortunately, at least so far, not very robust when applied to actual data – and are substantially more computationally sophisticated. See here for a recent preprint.  We have to do what we can with the measures we have, while always striving to generate and validate better measures.

4. I do not buy the claim that near-death-experiences provide an empirical challenge to physicalist neuroscience (as argued by Prof. Kelly). See my previous blog post on this issue (‘the brain’s last hurrah‘).

5. No need to impute me with a bias towards physicalism! I explicitly and happily adopt physicalism as a pragmatic metaphysics for pursuing a (neuro)science of consciousness.  I can do this while remaining agnostic about the actual ontological status of consciousness. The problem with many alternative metaphysics – in my view – is that they do not lead to testable propositions.  Dr Kastrup and Prof Kelly are of course entirely entitled to their own metaphysics. I was merely objecting to their usage of our psychedelic research in support of their metaphysics, because I think it is entirely irrelevant. I simply do not accept that there are any “evident tensions between physicalist expectations and the experimental results [from psychedelic neuroimaging]”.

6. Finally, we can hopefully all agree on the importance of forestalling, as far as possible, media misinterpretations.  This is true whatever one’s metaphysics.  And it’s why, when our diversity paper first appeared, I felt compelled to pen an immediate corrective right here in this blog (‘Evidence for a higher state of consciousness? Sort of‘).

After posting, I realized I had not specifically responded to Bernardo’s initial reaction to our Sci Am piece. There is some overlap with the above points, but please anyway allow me to correct this oversight here.

1. Clearing the semantic fog.  I hope I have made clear my intended distinction between ‘fully explain’ and ‘incrementally account for.’ Again my Aeon piece elaborates the strategy of refining explanatory mappings between mechanism and phenomenology.

2. Metaphysical claims. Our work is consistent with materialism and is motivated by it, but empirical studies like this are not suited to arbitrate between competing metaphysical positions (unless such positions state that there are no relations at all between brains and conscious experiences). Empirical studies like ours try to account for phenomenological properties in terms of mechanisms – but in doing so there is no need to make claims that one is addressing the (metaphysical) ‘hard problem’ of consciousness.  Kastrup and Kelly have written that “the psychedelic brain imaging research discussed here has brought us to a major theoretical decision point as to which framework best fits with all the available data” – where ‘physicalism’ is one among several (metaphysical) ‘frameworks’. I continue to think the research discussed here is irrelevant to this ‘decision point’, unless one is deciding to reject frameworks that postulate no relation between consciousness and the brain. The fact that the research is about psychedelics rather than (for example) psychophysics is neither here nor there.

3. What the researchers fail to address. I do not agree with the premise that there is an inconsistency between the dream state and the psychedelic state in terms of neural evidence. As noted above, measures of brain dynamics and activation are being continuously refined and innovated and it is overly simplistic to characterise the relevant dimensions in terms of gross ‘level of activity’.  Also, dreams and psychedelia are different. The point about ‘randomness’ I have  addressed already (diversity is not presented as an exhaustive explanation of psychedelic phenomenology).

4. A surprising claim. I respectfully refrain from addressing these points about the MRI/MEG studies since I was not involved with them. This does not mean I condone Bernardo’s comments. I will only repeat that brute measures of increased/decreased brain activity are less informative than more sophisticated measures of neural dynamics and connectivity, and studies are accumulating to more precisely map brain changes in psychedelic states.

5. The issue of statistics. It is not meaningful to compare, quantitatively, ‘magnitudes’ in changes in subjective experience with magnitudes of statistical effect size as applied to (for example) our diversity measures.  We made this point already in our Sci Am piece.  I find it quite natural to suppose that a massively meaningful change in subjective experience might have a subtle neuronal signature in the brain (and as I have said, diversity/randomness is only a small part of any full ‘explanation’ anyway).

6. A non-sequitur.  I do think its misleading to speak of a “formidable chasm” between “the magnitude of the subjective effects of a psychedelic trance and the accompanying physiological changes” for the reasons given in point 5 above.

7. Final thoughts. I indeed hope we can all agree that psychedelic research is interesting, exciting, valuable, evolving, clinically important, and generally highly worthwhile.  I hope we can also agree, as mentioned above, that forestalling media misrepresentations is important.  On other matters I doubt there will be full agreement between my views (and those of my colleagues) and Bernardo’s and Edward’s.  They are certainly entitled to their metaphysics. I simply wish to point out (i) our studies do help build explanatory bridges between neural mechanism and psychedelic phenomenology, and (ii) they do not provide any additional reasons to entertain non-physicalist metaphysics.

And with that, I’m afraid I’ll have to draw a line under this interesting discussion – at least for my involvement. I hope it generates some light amid the heat.

 

Conscious spoons, really? Pushing back against panpsychism

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So today I’d been planning to write about a new paper from our lab, just out in Neuropsychologia, in which we show how people without synaesthesia can be trained, over a few weeks, to have synaesthesia-like experiences – and that this training induces noticeable changes in their brains. It’s interesting stuff, and I will write about it later, but this morning I happened to read a recent piece by Olivia Goldhill in Quartz with the provocative title: “The idea that everything from spoons to stones are conscious is gaining academic credibility” (Quartz, Jan 27, 2018). This article had come up in a twitter discussion involving my colleague and friend Hakwan Lau about the challenge of maintaining the academic credibility of consciousness science, with Hakwan noting that provocative articles like this don’t often get the pushback they deserve.

So here’s some pushback.

Goldhill’s article is about panpsychism, which is the idea that consciousness is a fundamental property of the universe, present to some degree everywhere and in everything. Her article suggests that this view is becoming increasingly acceptable and accepted in academic circles, as so-called ‘traditional’ approaches (materialism and dualism) continue to struggle. On the contrary, although it’s true that panpsychism is being discussed more frequently and more openly these days, it remains very much a fringe proposition within consciousness science and is not taken seriously by many. Nor need it be, since consciousness science is getting along just fine without it. Let me explain how.

From hard problems to real problems

We should start with philosophy. Goldhill correctly identifies David Chalmers’ famous ‘hard problem of consciousness‘ as a key origin of modern panpsychism. This is bolstered by Chalmers’ own increasing apparent sympathy with this view, as Goldhill’s article makes clear. Put simply, the ‘hard problem’ is about how and why physical interactions of any sort can give rise to conscious experiences. This is indeed a difficult problem, and the apparent unavailability of any current solution is why those who fixate on it might be tempted by the elixir of panpsychism: if consciousness is ‘here, there, and everywhere‘ then there is no longer any hard problem to be solved.

But consciousness science has largely moved on from attempts to address the hard problem (though see IIT, below). This is not a failure, it’s a sign of maturity. Philosophically, the hard problem rests on conceivability arguments such as the possibility of imagining a philosophical ‘zombie’ – a behaviourally and perhaps physically identical version of me, or you, but which lacks any conscious experience, which has no inner universe. Conceivability arguments are generally weak since they often rest on failures of imagination or knowledge, rather than on insights into necessity. For example: the more I know about aerodynamics, the less I can imagine a 787 Dreamliner flying backwards. It cannot be done and such a thing is only ‘conceivable’ through ignorance about how wings work.

In practice, scientists researching consciousness are not spending their time (or their scarce grant money) worrying about conscious spoons, they are getting on with the job of mapping mechanistic properties (of brains, bodies, and environments) onto properties of consciousness. These properties can be described in many different ways, but include – for example – differences between normal wakeful awareness and general anaesthesia; experiences of identifying with and owning a particular body, or distinctions between conscious and unconscious visual perception. If you come to the primary academic meeting on consciousness science – the annual meeting of the Association for the Scientific Study of Consciousness (ASSC) – or read articles either in specialist journals like Neuroscience of Consciousness (I edit this, other journals are available) or in the general academic literature, you’ll find a wealth of work like this and very little – almost nothing – on panpsychism. You’ll find debates on the best way to test whether prefrontal cortex is involved in visual metacognition – but you won’t find any experiments on whether stones are aware. This, again, is maturity, not stagnation. It is also worth pointing out that consciousness science is having increasing impact in medicine, whether through improved methods for detecting residual awareness following brain injury, or via enhanced understanding of the mechanisms underlying psychiatric illness. Thinking about conscious spoons just doesn’t cut it in this regard.

A standard objection at this point is that empirical work touted as being about consciousness science is often about something else: perhaps memory, attention, or visual perception. Yes, some work in consciousness science may be criticized this way, but it is not generally the case. To the extent that the explanatory target of a study encompasses phenomenological properties, or differences between conscious states (e.g., dreamless sleep versus wakeful rest), it is about consciousness. And of course, consciousness is not independent of other cognitive and perceptual processes – so empirical work that focuses on visual perception can be relevant to consciousness even if it does not explicitly contrast conscious and unconscious states.

The next objection goes like this: OK, you may be able to account for properties of consciousness in terms of underlying mechanisms, but this is never going to explain why consciousness is part of the universe in the first place – it is never going to solve the hard problem. Therefore consciousness science is failing. There are two responses to this.

First, wait and see (and ideally do). By building increasingly sophisticated bridges between mechanism and phenomenology, the apparent mystery of the hard problem may dissolve. Certainly, if we stick with simplistic ‘explanations’ – for instance by associating consciousness simply with activity in (for example) the prefrontal cortex, everything may remain mysterious. But if we can explain (for example) the phenomenology of peripheral vision in terms of neurally-encoded predictions of expected visual uncertainty, perhaps we are getting somewhere. It is unwise to pronounce the insufficiency of mechanistic accounts of some putatively mysterious phenomenon before such mechanistic accounts have been fully developed. This is one reason why frameworks like predictive processing are exciting – they provide explanatorily powerful, computationally explicit, and empirically predictive concepts which can help link phenomenology and mechanism. Such concepts can help move beyond correlation towards explanation in consciousness science, and as we move further along this road the hard problem may lose its lustre.

Second, people often seem to expect more from a science of consciousness than they would ask of other scientific explanations. As long as we can formulate explanatorily rich relations between physical mechanisms and phenomenological properties, and as long as these relations generate empirically testable predictions which stand up in the lab (and in the wild), we are doing just fine. Riding behind many criticisms of current consciousness science are unstated intuitions that a mechanistic account of consciousness should be somehow intuitively satisfying, or even that it must allow some kind of instantiation of consciousness in an arbitrary machine. We don’t make these requirements in other areas of science, and indeed the very fact that we instantiate phenomenological properties ourselves, might mean that a scientifically satisfactory account of consciousness will never generate the intuitive sensation of ‘ah yes, this is right, it has to be this way’. (Thomas Metzinger makes this point nicely in a recent conversation with Sam Harris.)

Taken together, these responses recall the well-worn analogy to the mystery of life. Not so long ago, scientists thought that the property of ‘being alive’ could never be explained by physics or chemistry. That life had to be more than mere ‘mechanism’. But as biologists got on with the job of accounting for the properties of life in terms of physics and chemistry, the basic mystery of the ontological status of life faded away and people no longer felt the need to appeal to vitalistic concepts like ‘elan vital’. Now of course this analogy is imperfect, and from our current vantage it is impossible to say how closely it will stand up over time. Consciousness and life are not the same (though they may be more closely linked than people tend to think – another story!). But the basic point remains: instead of focusing on a possibly illusory big mystery – and thereby falling for the temptations of easy big solutions like panpsychism – the best strategy is to divide and conquer. Identify properties and account for them, and repeat. Chalmers’ himself describes something like this strategy when he talks about the ‘mapping problem’, and with tongue-somewhat-in-cheek I’ve called it ‘the real problem of consciousness‘.

The lure of integrated information theory

A major boost for modern panpsychism has come from Giulio Tononi’s much discussed – and fascinating – integrated information theory of consciousness (IIT). This is a formal mathematical theory which attempts to derive constraints on the mechanisms of consciousness from axioms about phenomenology. It’s a complex theory (and apparently getting more complex all the time) but the relevance for panpsychism is straightforward. On IIT, any mechanism that integrates information in the right way exhibits consciousness to some degree. And the ability to integrate information is very general, since it depends on only the cause-effect structure of a system.

Tononi actually goes further than this, in a crucial but subtle way. For him, the (integrated) information that counts is based not only what a system has done (ie., what states it has been in), but on what a system could do (i.e., what states it could be in, even if has never or will never occupy these states). Technically, this is the difference between the empirical distribution of a system and its maximum entropy distribution. This feature of IIT not only makes it hard (usually impossible) to calculate for nontrivial systems, it pushes further towards panpsychism because it implies an ontological status for certain forms of information – much like John Wheeler’s ‘it from bit‘. If (integrated) information is real (and therefore more-or-less everywhere), and if consciousness is based on (integrated) information, then consciousness is also more-or-less everywhere, thus panpsychism.

But this is not the only way to formulate IIT. Several years ago, Adam Barrett and I formulated a measure of integrated information which depends only on the empirical distribution of a system, and now many competing measures exist. These measures can be applied more easily in practice, and they do not directly imply panpsychism because they can be interpreted as explanatory bridges between mechanism and phenomenology (in the ‘real problem’ sense), rather than as claims about what consciousness actually is. So when Goldhill writes that IIT “shares the panpsychist view that physical matter has innate conscious experience” this is only true for the strong version of the theory articulated by Tononi himself. Other views are possible, and more empirically productive.

Back to science

This leads us to the main problem with panpsychism. It’s not that it sounds crazy, it’s that it cannot be tested. It does not lead to any feasible programme of experimentation. Progress in scientific understanding requires experiments and testability. Given this, it’s curious that Goldhill introduces us to Arthur Eddington, the physicist who experimentally confirmed Einstein’s (totally crazy-sounding) theory of general relativity. Eddington’s immense contribution to experimental physics should not give credence to his views on panpsychism, it should instead remind us of the essential imperative of formulating testable theories, however difficult such tests might be to carry out. (Modern physics is of course now facing a similar testability crisis with string theory.) And outlandish speculations about how quantum entanglement might lead to universe-wide consciousness have no place whatsoever in a rigorous and empirically grounded science of consciousness.

I can’t finish this post without noting that the current attention to panpsychism, especially in the media, has a lot to do with the views of some particularly influential figures in the field: Chalmers and Tononi, but also Christof Koch, whose early work with Francis Crick was fundamental in the rehabilitation of consciousness science in the late 1990s and who continues to be a major figure in the field. These people are all incredibly smart and have made extremely important contributions within consciousness science and beyond. I have learned a great deal from each, and I owe them intellectual debts I will never be able to repay. Having said that, their views on panpsychism are firmly in the minority and should not be over-weighted simply because of their historical contributions and current prominence. Whether there is something about having made such influential contributions that leads to a tendency to adopt countercultural (and difficult to test) views later on – well that’s for another day and another writer.

At the end of her piece, Goldhill quotes Chalmers quoting the philosopher John Perry who says: “If you think about consciousness long enough, you either become a panpsychist or you go into administration.” Perhaps the problem lies in only thinking. We should instead complement only thinking with the challenging empirical work of explaining properties of consciousness in terms of biophysical mechanisms. Then we can say: If you work on consciousness long enough, you either become a neuroscientist or you become a panpsychist. I know where I’d rather be – with my many colleagues who are not worrying about conscious spoons but who are trying, and little-by-little succeeding, in unravelling the complex biophysical mechanisms that shape our subjective experiences of world and self. And now it’s high time I got back to that paper on training synaesthesia.

(For more general discussions about consciousness science, where it’s at and where we’re going, have a listen to my recent conversation with Sam Harris. Make sure you have time for it though, it clocks in at over three hours …)

Evidence for a higher state of consciousness? Sort of.

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Bicycle Day Celebration Blotter.  By YttriumOx CC BY-SA 3.0

On April 19 1943, seventy-four years ago to the day, Albert Hoffman conducted his now famous self-experimentation on the psychological effects of LSD, a compound he had been the first to synthesize some years earlier. Now called ‘bicycle day’ in honour of how Hoffman made his way home, it led to some remarkable descriptions:

“… Little by little I could begin to enjoy the unprecedented colors and plays of shapes that persisted behind my closed eyes. Kaleidoscopic, fantastic images surged in on me, alternating, variegated, opening and then closing themselves in circles and spirals, exploding in colored fountains, rearranging and hybridizing themselves in constant flux …”

In the decades that followed, academic research into LSD and other psychedelics was cast into the wilderness as worries about their recreational use held sway. Recently, however, the tide has started to turn. There is now gathering momentum for studies showing a remarkable clinical potential for psychedelics in treating recalcitrant psychiatric disorders, as well as experiments trying to understand how psychedelics exert their distinctive effects on conscious experience.

In a new paper published in Scientific Reports on this bicycle day anniversary, we describe a distinctive neuronal signature of the psychedelic state: a global increase in neuronal signal diversity. So – is this evidence for a ‘higher state’ of consciousness? And could it account for the nature of psychedelic experience? Let me answer these questions by summarizing what we did.

Our study analyzed data previously collected by Dr. Robin Carhart-Harris (Imperial College London) and Dr. Suresh Muthukumaraswamy (then Cardiff, now at Auckland). These were magnetoencephalographic (MEG) brain-imaging data from healthy volunteers either in a normal waking state, or after having taken LSD, psylocibin (the active ingredient in magic mushrooms) or ketamine (which in low doses acts as a psychedelic – in high doses it has an anaesethetic effect). MEG data combine a very high temporal resolution, with a much better spatial resolution than EEG (electroencephalography), allowing us to compute some relatively sophisticated mathematical measures of signal diversity. The participants in our study had passed strict ethical criteria, and were asked simply to rest quietly in the scanner during the experiment. Afterwards, they were asked various questions about what they had experienced.

With Carhart-Harris and Muthukumaraswamy, and with Dr. Adam Barrett and first-author Michael Schartner of the Sackler Centre for Consciousness Science here at Sussex, we chopped up the MEG data into small segments and for each segment calculated a range of different mathematical measures. The most interesting is called ‘Lempel Ziv (LZ) complexity,’ which measures the diversity of the data by figuring out how ‘compressible’ it is. A completely random data sequence would be maximally diverse since it is not compressible at all. A completely uniform data sequence would be minimally diverse since it is easy to compress. In fact, because of these properties the algorithm for computing LZ complexity is widely used to compress digital photos into smaller files, in an optimal way.

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Changes in LZ complexity under LSD, as compared to the waking state.  Data are source localized MEG.  Image from Suresh Muthukumaraswamy and appears in Figure 3 in the paper.

We found that MEG signals had a reliably higher level of LZ – and hence signal diversity – for all three psychedelic compounds, with perhaps the strongest effects for LSD. The fact that we found the same pattern of results across all three psychedelic compounds is both striking and reassuring – it means our results are not likely to have arisen by chance.

Intuitively, these findings mean that the brain-on-psychedelics is less predictable, more random – and more diverse than in the normal waking state.

Our data can be thought of as evidence for a ‘higher’ state of consciousness only in this very specific way, and only in the context provided by other studies where a loss of consciousness has been associated with a reduction of neuronal diversity. For example, studies in our lab have shown reduced LZ complexity (reduced diversity) for both anaesthesia and for (non-dreaming) sleep. (Interestingly, levels of LZ returned to ‘normal’ during REM sleep when dreams are likely.) What’s striking about our results, in this context, is that increases in quantitative measures of conscious level, compared to the waking state, have never been found before.

Interpreting our data in terms of conscious level also make sense since measures of signal diversity, like LZ, can be thought of as approximations to related quantities like the ‘perturbation complexity index’ (PCI). This measure captures the diversity of the brain’s response to an electromagnetic stimulus: think banging on the brain (but using transcranial magnetic stimulation which applies a sharp electromagnetic ‘bang’), and listening to the echo. Studies using PCI, pioneered by Prof. Marcello Massimini at the University of Milan, have found a remarkable sensitivity to changes in conscious level, and even an ability to predict residual consciousness in devastating neurological conditions like coma and the vegetative state. The differences between LZ and PCI are subtle, having mainly to do with whether they measure simple diversity or a mixture of diversity and ‘integration’ in brain dynamics.

More generally, measures of diversity are related to influential theories which associate consciousness with ‘integrated information’ or ‘causal density’ in the dynamics of the brain. While these theories specify even more complicated mathematical measures of conscious level, the fact that we see measurable increases in diversity so reliably across conscious states gives some support to these theories.  Our results are also consistent with Robin Carhart-Harris’ ‘entropic brain‘ theory, which proposes that the psychedelic state is associated with greater entropy or uncertainty in neural dyamics.

In this broader theoretical context, what’s interesting about our results is that they show that a measure of conscious level – previously applied to sleep and anesthesia – is also sensitive to differences in conscious content, as in the contrast between the psychedelic state and normal wakefulness. This helps shed some new light on an old debate in the science of consciousness – the relationship between conscious level (how conscious you are) and conscious content (what you’re conscious of, when you’re conscious).

Taking this research forward, we plan to understand more about how specific properties of neural dynamics relate to specific properties of psychedelic experiences. In the present study, we found some tentative correlations between changes in signal diversity and the degree to which people reported experiences like ‘ego dissolution’ and ‘vividness of imagination’. However, these correlations were not strong. One possible reason is that the subjective reports were taken outside the scanner, likely some time after the peak effect of the drug. Another possibility – which we are currently looking into – is that more fine-grained measures of information flow in the brain, like Granger causality, might be needed in order to closely map properties of psychedelic experience to changes in the brain.

Overall, our study adds to a growing body of work – much of which has been led by Carhart-Harris and colleagues –  that is now revealing the brain-basis of the psychedelic state. Our data show that a simple measure of neuronal signal diversity places the psychedelic state ‘above’ the normal waking state, in comparison to the lower diversity found in sleep and anesthesia. Taking this work forward stands to do much more than enhance our understanding of psychedelics. It may help expose how, why – and for whom – psychedelics may help alleviate the appalling suffering of psychiatric disorders like depression. And in the end, it may help us figure out how our normal everyday conscious experiences of the world, and the self, come to be.

After all, everything we experience – even when stone cold sober – is just a kind of ‘controlled hallucination.’ Our perceptions are just the brain’s “best guess” of what’s going on, reined in by sensory signals. It’s just that most of the time we agree with each other about our hallucinations, and call them reality.

‘Increased spontaneous MEG signal diversity for psychoactive doses of ketamine, LSD and psilocybin’ by Michael Schartner, Robin Carhart-Harris, Adam Barrett, Anil Seth and Suresh Muthukumaraswamy is published in Scientific Reports (7): 46421, 2017. It is freely available here as an open-access publication. I am the corresponding author.

The study has been extensively covered in the media. Particularly good pieces are in The Guardian in the New Scientist and in Wired. There is also a highly active Reddit thread, which on the day of publication was consistently on the Reddit homepage. 

I would like to specifically acknowledge Michael Schartner and Adam Barrett in this post.  Michael’s Ph.D. – awarded just a few months ago – was all about measuring signal diversity in various different conscious states (sleep, anesthesia, psychedelia. Michael was primarily supervised by Dr. Barrett who devoted his considerable mathematical expertise to the project. Very many thanks are also due to Robin Carhart-Harris and Suresh Muthukumaraswamy for generously engaging with this collaboration.

Carhart-Harris, Muthukumaraswamy and colleagues have published a number of other important studies on the neural basis of the psychedelic state.  See here and here – or just look on PubMed.

The real problem

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aeon_coverWhat is the best way to understand consciousness? In philosophy, centuries-old debates continue to rage over whether the Universe is divided, following René Descartes, into ‘mind stuff’ and ‘matter stuff’. But the rise of modern neuroscience has seen a more pragmatic approach gain ground: an approach that is guided by philosophy but doesn’t rely on philosophical research to provide the answers. Its key is to recognise that explaining why consciousness exists at all is not necessary in order to make progress in revealing its material basis – to start building explanatory bridges from the subjective and phenomenal to the objective and measurable.

This is the start of an essay I recently wrote for the website aeon.co, which publishes an essay a day, focusing on ideas and culture.  The basic idea is to chart a pragmatic path for the scientific study of consciousness, respecting but not directly targeting the deep metaphysical mysteries so eloquently exposed by Chalmers’ famous distinction between the ‘easy’ and ‘hard’ problems.  Much of what I say has been said before (e.g., in the tradition of neurophenomenology) but I hope to bring things together in a new way and with a distinctive empirical angle.  Anyway, best make up your own mind – I’d be keen to hear what you think!

At the edges of awareness

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Imagine this. Following a brain injury you lie in a hospital bed and from the outside you appear to be totally unconscious. You don’t respond to anything the doctors or your family say, you make no voluntary movements, and although you still go to sleep and wake up there seems to be nobody at home. But your ‘inner universe’ of conscious awareness still remains, perhaps flickering and inconsistent, but definitely there. How could anyone else ever know, and how could you ever communicate with your loved ones again?

Two new radio dramas, The Sky is Wider and Real Worlds, engage with these critical questions by drawing on the cutting edge of the neurology and neuroscience. Recent advances have enabled researchers to not only diagnose ‘residual’ awareness following severe brain injuries, but also to open new channels of communication with behaviourally unresponsive patients. The key medical challenge is to distinguish between the so-called ‘vegetative state’ in which there truly is no conscious awareness, from ‘minimally conscious’ or ‘locked-in’ conditions where some degree of consciousness persists (even normal consciousness, in the locked-in state), even though there are no outward signs.

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Brain activity during mental imagery, in a behaviourally unresponsive patient and in a  control subject.  Source: MRC via The Guardian

Linda Marshall Griffith’s drama The Sky is Wider takes inspiration from an ‘active approach’ in which the neurologist asks questions of the patient and monitors their brain activity for signs of response. In a classic study from about 10 years ago, Adrian Owen and his team asked behaviourally unresponsive patients to imagine either walking around their house or playing tennis, while their brains were scanned using functional MRI (which measures regional metabolic activity in the brain). These questions were chosen because imagining these different behaviours activates different parts of the brain, and so if we see these selective activations in a patient, we know that they have understood and are voluntarily following the instructions. If they can do this, they must be conscious. It turns out that between 10-20% of patients behaviourally diagnosed as being in the vegetative state can pass this test. Equally important, this same method can be used to establish simple communication by (for example) asking a patient to imagine playing ‘tennis’ to answer ‘yes’ and walking around a house to answer ‘no’.

These developments represent a revolution in clinical neurology. Current research is increasing the efficiency of active approaches by using the more portable electroencephalography (EEG) instead of bulky and expensive MRI. ‘Passive’ techniques in which residual consciousness can be inferred without requiring patients to perform any task are also rapidly improving. These methods are important because active approaches may underestimate the incidence of residual awareness since not all conscious patients may understand or be able to follow verbal instructions.

Alongside these scientific developments we encounter pressing ethical questions. How should we treat patients in these liminal states of awareness? And given a means of communication, what kinds of questions should we ask? The Sky is Wider explores these challenging ethical issues in a compelling narrative which gives dramatic voice to the mysterious conditions of the vegetative and minimally conscious states.

 

In Real Worlds, Jane Rogers takes us several years into the future. Communication with behaviourally unresponsive patients is now far advanced and is based on amazing developments in ‘virtual reality’. The clinical context for this drama is the ‘locked-in syndrome’ where a patient may have more-or-less normal conscious experiences but completely lack the ability to move. In Real Worlds, a locked-in patient transcends these limitations by controlling a virtual reality avatar directly using brain signals. These avatars inhabit virtual worlds in which the avatars of different people can interact, while the ‘real’ person behind each may remain hidden and unknown.

This drama deliberately inhabits the realm of science fiction, but there is solid science behind it too. The development of so-called ‘brain computer interfaces’ (BCI) is moving fast. These interfaces combine brain imaging methods (like EEG or fMRI, or sometimes more ‘invasive’ methods’ in which electrodes are inserted directly into the brain) with advanced machine learning methods to perform a kind of ‘brain-reading’. The idea is to infer, from brain activity alone, intended movements, perceptions, and perhaps even thoughts. These decoded ‘thoughts’ can then be used to control robotic devices, or virtual avatars. In some cases, a person’s own body might be controlled via direct stimulation of muscles. Progress in this area has been remarkably rapid. In a landmark but rather showy example, the Brazilian neuroscientist Miguel Nicolelis used a BCI to allow a paralysed person to ‘kick’ the first ball of the 2014 football world cup, through brain-control of a robotic avatar. More recently, brain-reading methods have allowed a paralysed man to play Guitar Hero for the first time since his injury.

The other technology highlighted in Real Worlds is virtual reality (VR), which – thanks to its enormous consumer potential – is developing even more rapidly. All the major technology and AI companies are getting in on the act, and VR headsets are finally becoming cheap enough, comfortable enough, and powerful enough to define a new technological landscape. Here at the Sackler Centre for Consciousness Science at the University of Sussex, we are exploring how VR can help shed light on our normal conscious experience. In one example, we use a method called ‘augmented reality’ (AR) to project a ‘virtual’ body into the real world as seen through a camera mounted on the front of a VR headset. This experiment revealed how our perception of what is (and what is not) our own body can be easily manipulated, indicating that our experience of ‘body ownership’, which is so easy to take for granted, is in fact continuously and actively generated by the brain. In a second example, we developed a method called ‘substitutional reality’ in which a VR headset is coupled with panoramic video and audio taken from a real environment, manipulated in various ways. The resulting experiences are much more immersive than current computer-generated virtual environments and in some cases people cannot distinguish them from actually ‘real’ environments.

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A ‘virtual reality’ hand, part of a Sackler Centre study to explore the mechanisms underlying experiences of body ownership.  VR programming by Dr. Keisuke Suzuki.

Just as in the first drama, ethical questions risk outpacing the science and technology. As VR becomes increasingly immersive and pervasive, its potential to impact our real lives is ever more powerful. While benefits are easy to imagine – for instance in bringing distant relatives together or enabling remote experiences of inaccessible places – there are also legitimate concerns. High on the list would be what happens if people become increasingly unable to distinguish the real world from the virtual, whether in the moment or (more plausibly) in their memories. And what if they progressively withdrew from ‘reality’ if the available virtual worlds became more appealing places to be? Of course, simple dichotomies are unhelpful since VR technologies are part of our real worlds, just like mobile phones and laptop computers. Jane Rogers’ Real Worlds explores these complex ethical issues by imagining VR as a future treatment – perhaps ‘prosthesis’ would be a better word – for the disorders of consciousness like those encountered in The Sky is Wider.

Together, these dramas explore the human and societal consequences of existing and near-future clinical technologies. With artistic license they ask important questions that scientists and clinicians are not yet equipped to address. Ultimately, I think they convey an optimistic message, that we can understand and treat – if not cure – severely debilitating conditions that may otherwise have remained undiagnosed let alone treated. But they also lead us to consider, not just what we could do, but what we should do.

The Sky is Wider (written by Linda Marshall Griffiths) and Real Worlds (written by Jane Rogers) were produced by Nadia Molinari for BBC Radio 4. I acted as the scientific consultant. The original ideas were formulated during a 2014 Wellcome Trust ‘Experimental Stories’ workshop in a conversation between myself, Nadia, and Linda.

The science of selfhood

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lorna-zoe-wanamaker-by-johan-persson2-1200x800.jpgZoë Wanamaker as Lorna in Nick Payne’s Elegy.

“The brain is wider than the sky,
For, put them side by side,
The one the other would contain,
With ease, and you besides”

Emily Dickinson, Complete Poems, 1924

What does it mean to be a self? And what happens to the social fabric of life, to our ethics and morality, when the nature of selfhood is called into question?

In neuroscience and psychology, the experience of ‘being a self’ has long been a central concern. One of the most important lessons, from decades of research, is that there is no single thing that is the self. Rather, the self is better thought of as an integrated network of processes that distinguish self from non-self at many different levels. There is the bodily self – the experience of identifying with and owning a particular body, which at a more fundamental level involves the amorphous experience of being a self-sustaining organism. There is the perspectival self, the experience of perceiving the world from a particular first-person point-of-view. The volitional self involves experiences of intention of agency, of urges to do this-or-that (or, perhaps more importantly, to refrain from doing this-or-that) and of being the cause of things that happen.

At higher levels we encounter narrative and social selves. The narrative self is where the ‘I’ comes in, as the experience of being a continuous and distinctive person over time. This narrative self – the story we tell ourselves about who we are – is built from a rich set of autobiographical memories that are associated with a particular subject. Finally, the social self is that aspect of my self-experience and personal identity that depends on my social milieu, on how others perceive and behave towards me, and on how I perceive myself through their eyes and minds.

In daily life, it can be hard to differentiate these dimensions of selfhood. We move through the world as seemingly unified wholes, our experience of bodily self seamlessly integrated with our memories from the past, and with our experiences of volition and agency. But introspection can be a poor guide. Many experiments and neuropsychological case studies tell a rather different story, one in which the brain actively and continuously generates and coordinates these diverse aspects of self-experience.

The many ways of being a self can come apart in surprising and revealing situations. For example, it is remarkably easy to alter the experience of bodily selfhood. In the so-called ‘rubber hand illusion,’ I ask you to focus your attention on a fake hand while your real hand is kept out of sight. If I then simultaneously stroke your real hand and the fake hand with a soft paintbrush, you may develop the uncanny feeling that the fake hand is now, somehow, part of your body. A more dramatic disturbance of the experience of body ownership happens in somatoparaphrenia, a condition in which people experience that part of their body is no longer theirs, that it belongs to someone else – perhaps their doctor or family member. Both these examples involve changes in brain activity, in particular within the ‘temporo-parietal junction’, showing how even very basic aspects of personal identity are actively constructed by the brain.

Moving through levels of selfhood, autoscopic hallucinations involve seeing oneself from a different perspective, much like ‘out of body’ experiences. In akinetic mutism, people seem to lack any experiences of volition or intention (and do very little), while in schizophrenia or anarchic hand syndrome, people can experience their intentions or voluntary actions as having external causes. At the other end of the spectrum, disturbances of social self emerge in autism, where difficulties in perceiving others’ states of mind seems to be a core problem, though the exact nature of the autistic condition is still much debated.

When it comes to the ‘I’, memory is the key. Specifically, autobiographical memory: the recollection of personal experiences of people, objects, and places and other episodes from an individual’s life. While there are as many types of memory as there are varieties of self (for example, we have separate memory processes for facts, for the short term and the long term, and for skills that we learn), autobiographical memories are those most closely associated with our sense of personal identity. This is well illustrated by some classic medical cases in which, as a result of surgery or disease, the ability to lay down new memories is lost. In 1953 Henry Moliason (also known as the patient HM) had large parts of his medial temporal lobes removed in order to relieve severe epilepsy. From 1957 until his death in 2008, HM was studied closely by the neuropsychologist Brenda Milner, yet he was never able to remember meeting her. In 1985 the accomplished musician Clive Wearing suffered a severe viral brain disease that affected similar parts of his brain. Now 77, he frequently believes he has just awoken from a coma, spending each day in a constant state of re-awakening.

Surprisingly, both HM and Wearing remained able to learn new skills, forming new ‘procedural’ memories, despite never recalling the learning process itself. Wearing could still play the piano, and conduct his choir, though he would immediately forget having done so. The music appears to carry him along from moment to moment, restoring his sense of self in a way his memory no longer can. And his love for his wife Deborah seems undiminished, so that he expresses an enormous sense of joy on seeing her, even though he cannot tell whether their last meeting was years, or seconds, in the past. Love, it seems, persists when much else is gone.

For people like HM and Clive Wearing, memory loss has been unintended and unwanted. But as scientific understanding develops, could we be moving towards a world where specific memories and elements of our identity can be isolated or removed through medical intervention? And could the ability to lay down new memories ever be surgically restored? Some recent breakthroughs suggest these developments may not be all that far-fetched.

In 2013, Jason Chan and Jessica LaPaglia, from Iowa State University showed that specific human memories could indeed be deleted. They took advantage of the fact that when memories are explicitly recalled they become more vulnerable. By changing details about a memory, while it was being remembered, they induced a selective amnesia which lasted for at least 24 hours. Although an important advance, this experiment was limited by relying on ‘non-invasive’ methods – which means not using drugs or directly interfering with the brain.

More recent animal experiments have shown even more striking effects. In a ground-breaking 2014 study at the University of California, using genetically engineered mice, Sadegh Nabavi and colleagues managed to block and then re-activate a specific memory. They used a powerful (invasive) technique called optogenetics to activate (or inactivate) the biochemical processes determining how neurons change their connectivity. And elsewhere in California, Ted Berger is working on the first prototypes of so-called ‘hippocampal prostheses’ which replace a part of the brain essential for memory with a computer chip. Although these advances are still a long way from implementation in humans, they show an extraordinary potential for future medical interventions.

The German philosopher Thomas Metzinger believes that “no such things as selves exist in the world”. Modern neuroscience may be on his side, with memory being only one thread in the rich tapestry of processes shaping our sense of selfhood. At the same time, the world outside the laboratory is still full of people who experience themselves – and each other – as distinct, integrated wholes. How the new science of selfhood will change this everyday lived experience, and society with it, is a story that is yet to be told.

Originally commissioned for the Donmar Warehouse production of Elegy, with support from The Wellcome Trust.  Reprinted in the programme notes and in Nick Payne’s published script.

Tracing the edges of consciousness

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As a scientist, consciousness has always fascinated me. But understanding consciousness is not a project for science alone. Throughout history, philosophers, artists, storytellers, and musicians have all wondered about the apparent miracle of conscious awareness. Even today, while science might give us our best shot at figuring out the brain – the organ of experience – we need, more than ever, a melding of the arts and sciences, of contemporary and historical approaches, to understand what consciousness really is, to grasp what we mean by, as Mark Haddon eloquently puts it, “Life in the first person.”

This quote comes from Haddon’s beautiful introductory essay to a major new exhibition at the Wellcome Collection in London. Curated by Emily Sargent, States of Mind: Tracing the edges of consciousness “examines perspectives from artists, psychologists, philosophers and neuroscientists to interrogate our understanding of the conscious experience”. Its a fantastic exhibition, with style and substance, and I feel very fortunate to have been involved as an advisor from its early stages.

What’s so special about consciousness?

Consciousness is at once the most familiar and the most mysterious aspect of our existence. Conscious experiences define our lives, but the private, subjective, and what-it-is-likeness of these experiences seems to resist scientific enquiry. Somehow, within each our brains the combined activity of many billions of neurons, each one a tiny biological machine, is giving rise to a conscious experience. Your conscious experience: right here, right now, reading these words. How does this happen? Why is life in the first person?

In one sense, this seems like the kind of mystery ripe for explanation. Borrowing again from Mark Haddon, the raw material of consciousness is not squirreled away deep inside an atom, its not happening 14 billion years ago, and its not hiding out on the other side of the universe. It’s right here in front of – or rather behind – our eyes. Saying this, the brain is a remarkably complex object. It’s not so much the sheer number of neurons (though there about 90 billion). It’s the complexity of its wiring: there are so many connections, that if you counted one every second it would take you 3 million years to finish. Is it not possible that an object of such extraordinary complexity should be capable of extraordinary things?

People have been thinking about consciousness since they’ve been thinking at all. Hippocrates, the founder of modern medicine, said: “Men ought to know that from the brain, and from the brain only, arise our pleasures, joys, laughter and jests, as well as our sorrows, pains, griefs and tears … Madness comes from its moistness.” (Aristotle, by the way, got it wrong, thinking the brain hadn’t much to do with consciousness at all.)

Fast forward to Francis Crick, whose ‘astonishing hypothesis’ in the 1990s deliberately echoed Hippocrates: “You, your joys and your sorrows, your memories and your ambitions … and so on … are in fact no more than the behaviour of a vast assembly of nerve cells and their associated molecules”. Crick, who I was lucky enough to meet during my time in America, was working on the neurobiology of consciousness even on the day he died. You will see some of his personal notes, and his perplexing plasticine brain models, in States of Mind.

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Descartes: view of posterior of brain, from De Hominem. Wellcome Collection

A major landmark in thinking about consciousness is of course Descartes, who in the 17th Century distinguished between “mind stuff” (res cogitans) and “matter stuff” (res extensa), so giving rise to the now infamous mind-body problem and the philosophy of dualism. Its a great thrill for to see an original copy of Descartes’ De Homine as part of this exhibition. Its modern incarnation as David Chalmers’ so-called ‘hard problem’ has recently gained enough cultural notoriety even to inspire a Tom Stoppard play (though for my money Alex Garland’s screenplay for Ex Machina is the more perspicuous). The idea of the hard problem is this: Even if we knew everything about how the operations of the brain give rise to perception, cognition, learning, and behaviour a problem would still remain: why and how any of this should be associated with consciousness at all? Why is life in the first person?

Defining consciousness

How to define consciousness? One simple definition is that for a conscious organism there is something it is like to be that organism. Or, one can simply say that consciousness is what disappears when we fall into a dreamless sleep, and what returns when we wake up or start dreaming. A bit more formally, for conscious organisms there exists a continuous (though interruptible) stream of conscious scenes – a phenomenal world – which has the character of being subjective and private. The material in States of Mind can help us encounter these ideas with a bit more clarity and force, by focusing on the edges – the liminal boundaries – of consciousness.

First there is conscious level: the difference between being awake and, let’s say, under general anaesthesia. Here, neuroscience now tells us that there is no single ‘generator’ of consciousness in the brain, rather, being consciousness depends on highly specific ways in which different parts of the brain speak to each other. Aya Ben Ron’s film of patients slipping away under anaesthesia is a beautiful exploration of this process, as is the whole section on ‘SLEEP | AWAKE’.

Then there is conscious content: what we are conscious of, when we are conscious. These are the perceptions, thoughts, and emotions that populate our ever-flowing stream of awareness. Here, current research is revealing that our perceptual world is not simply an internal picture of some external reality. Rather, conscious perception depends on the brain’s best guesses, or hypotheses, about the causes of sensory data. Perception is therefore a continuously creative act that is tightly bound up with imagination, so that our experience of the world is a kind of ‘controlled hallucination’, a fantasy that – usually, but not always – coincides with reality. The material on synaesthesia in States of Mind beautifully illuminates this process by showing how, for some of us, these perceptual fantasies can be very different – that we all have our own distinctive inner universes. You can even try training yourself to become a ‘synaesthete’ with a demo of some of our own research, developed for this exhibition. Many thanks to Dr. David Schwartzman of the Sackler Centre for making this happen.

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Alphabet in Colour: Illustrating Vladimir Nabokov’s grapheme-colour synaesthesia, by Jean Holabird.

Finally there is conscious self – the specific experience of being me, or being you. While this might seem easy to take for granted, the experience of being a self requires explanation just as much as any other kind of experience. It too has its edges, its border regions. Here, research is revealing that conscious selfhood, though experienced as unified, can come apart in many different ways. For example, our experience of being and having a particular body can dissociate from our experience of being a person with name and a specific set of memories. Conscious selfhood, like all conscious perception, is therefore another controlled hallucination maintained by the brain. The section BEING | NOT BEING dramatically explores some of these issues, for example by looking at amnesia with Shona Illingworth, and with Adrian Owen’s seminal work on the possibility of consciousness even after severe brain injury.

This last example brings up an important point. Besides the allure of basic science, there are urgent practical motivations for studying consciousness. Neurological and psychiatric disorders are increasingly common and can often be understood as disturbances of conscious experience. Consciousness science promises new approaches and perhaps new treatments for these deeply destructive problems. Scoping out further boundary areas, studying the biology of consciousness can shed new light on awareness in newborn infants and in non-human animals, informing ethical debates in these areas. Above all, consciousness science carries the promise of understanding more about our place in nature. Following the tradition of Copernicus and Darwin, a biological account of conscious experience will help us see ourselves as part of, not apart from, the rest of the universe.

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Santiago Ramon y Cajal, distinguishing the reticular theory (left) from the neuron doctrine (right).  From the Instituto Cajal, Madrid.

Let’s finish by returning to this brilliant exhibition, States of Mind. What I found most remarkable are the objects that Emily Sargent has collected together. Whether its Descartes’ De Hominem, Ramon y Cajal’s delicate ink drawings of neurons, or Francis Crick’s notebooks and models, these objects bring home and render tangible the creativity and imagination which people have brought to bear in their struggle to understand consciousness, over hundreds of years. For me, this brings a new appreciation and wonder to our modern attempts to tackle this basic mystery of life. Emily Dickinson, my favourite poet of neuroscience, put it like this. “The brain is wider than the sky, for – put them side by side – the one the other will contain, with ease, and you – beside.”

States of Mind is at the Wellcome Collection in London from Feb 4th until October 16th 2016 and is curated by Emily Sargent. Sackler Centre researchers, in particular David Schwartzman and myself,  helped out as scientific advisors. This text is lightly adapted from a speech I gave at the opening event on Feb 3rd 2016. Watch this space, and visit the exhibition website, for news about special events on consciousness that will happen throughout the year.

States of Mind at the Wellcome Collection

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YellowPinkBlue by Ann Veronica Janssens

From October 2015 until October 2016 the Wellcome Collection in London is curating an exhibition called States of Mind: Tracing the Edges of Consciousness.  It has been launched with a brilliant piece of installation art by Ann Veronica Janssens (until 3rd Jan 2016).  In YellowPinkBlue the entire gallery space is invaded by coloured mist, to focus attention on the process of perception itself so that one becomes subsumed by the experience of seeing.  I’m excited to be contributing in various ways to States of Mind, via the Sackler Centre (more on that soon). To start with, here is the text I wrote for Janssen’s remarkable piece.

What in the world is consciousness?

Right now an apparent miracle is unfolding. Within your brain, the electrochemical activity of many billions of richly interconnected brain cells – each one a tiny biological machine – is giving rise to a conscious experience. Your conscious experience: right here, right now, reading these words.

It is all too easy to go about our daily lives, having conscious experiences, without appreciating how remarkable it is that we have these experiences at all. Ann Veronica Janssens’s piece returns us to the sheer wonder of being conscious. By stripping away many of the features that permeate our normal conscious lives, the raw fact of experiencing is given renewed emphasis.

People have wondered about consciousness since they’ve wondered about anything. Hippocrates, the Greek founder of modern medicine, rightly identified the brain as the organ of experience (though Aristotle didn’t agree). In the Renaissance, Descartes divided the universe into ‘mind stuff’ (res cogitans) and ‘matter stuff’ (res extensa), giving birth to the philosophy of dualism and the confounding ‘mind–body’ problem of how the two relate. In the 19th century, when psychology first emerged as a science, understanding consciousness was its primary objective. Though largely sidelined during the 20th century, the challenge of revealing the biological basis of consciousness is now firmly re-established for our times. Janssens’s piece reminds us of the important distinction in science between being conscious at all (conscious level: the difference between being awake and being in a dreamless sleep or under anaesthesia) and what we are conscious of (conscious content: the perceptions, thoughts and emotions that populate our conscious mind). There is also conscious selfhood – the specific experience of being me (or you). Each of these aspects of consciousness can be traced to specific mechanisms in the brain that neuroscientists, in cahoots with researchers from many other disciplines, are now starting to unravel. There are many exciting ideas in play, ranging from the dependence of conscious level on how different parts of the brain speak to each other, to understanding conscious content as determined by the brain’s ‘best guess’ of the causes of ambiguous and noisy sensory signals. Crucially, these ideas have allowed consciousness science to progress from the philosopher’s armchair to the research laboratory.

Besides the allure of basic science, there are important practical motivations for studying consciousness. Neurological and psychiatric disorders are increasingly common and can often be framed as disturbances of conscious experience. Consciousness science promises new approaches and perhaps new treatments for these scourges of modern society. New theories and experiments can also shed light on consciousness in newborns and in non-human animals, adding critical information to important ethical debates in these areas. But above all, consciousness science carries the promise of understanding more about our place in nature. Following Darwin and Copernicus, a biological account of conscious experience will help us see ourselves as part of, not apart from, the rest of the universe.

Anil Seth, Professor of Cognitive and Computational Neuroscience
Co-Director, Sackler Centre for Consciousness Science, University of Sussex