Monthly Archives: January 2014

The limpid subtle peace of the ecstatic brain

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In Dostoevsky’s “The Idiot”, Prince Mychkine experiences repeated epileptic seizures accompanied by “an incredible hitherto unsuspected feeling of bliss and appeasement”, so that “All my problems, doubts and worries resolved themselves in a limpid subtle peace, with a feeling of understanding and awareness of the ‘Supreme Principal of life’”. Such ‘ecstatic epileptic seizures’ have been described many times since (usually with less lyricism), but only now is the brain basis of these supremely meaningful experiences becoming clear, thanks to remarkable new studies by Fabienne Picard and her colleagues at the University of Geneva.

Ecstatic seizures, besides being highly pleasurable, involve a constellation of other symptoms including an increased vividness of sensory perceptions, heightened feelings of self-awareness – of being “present” in the world – a feeling of time standing still, and an apparent clarity of mind where all things seem suddenly to make perfect sense. For some people this clarity involves a realization that a ‘higher power’ (or Supreme Principal) is responsible, though for atheists such beliefs usually recede once the seizure has passed.

In the brain, epilepsy is an electrical storm. Waves of synchronized electrical activity spread through the cortex, usually emanating from one or more specific regions where the local neural wiring may have gone awry.  While epilepsy can often be treated by medicines, in some instances surgery to remove the offending chunk of brain tissue is the only option. In these cases it is now becoming common to insert electrodes directly into the brains of surgical candidates, to better localize the ‘epileptic focus’ and to check that its removal would not cause severe impairments, like the loss of language or movement.  And herein lie some remarkable new opportunities.

Recently, Dr. Picard used just this method to record brain activity from a 23-year-old woman who has experienced ecstatic seizures since the age of 12. Picard found that her seizures involved electrical brain-storms centred on a particular region called the ‘anterior insula cortex’.  The key new finding was that electrical stimulation of this region, using the same electrodes, directly elicited ecstatic feelings – the first time this has been seen. These new data provide important support for previous brain-imaging studies which have shown increased blood flow to the anterior insula in other patients during similar episodes.

The anterior insula (named from the latin for ‘island’) is a particularly fascinating lump of brain tissue.  We have long known that it is involved in how we perceive the internal state of our body, and that these perceptions underlie emotional experiences. More recent evidence suggests that the subjective sensation of the passing of time depends on insular activity.  It also seems to be the place where perceptions of the outside world are integrated with perceptions of our body, perhaps supporting basic forms of self-consciousness and underpinning how we experience our relation to the world.  Strikingly, abnormal activity of the insula is associated with pathological anxiety (the opposite of ecstatic ‘certainty’) and symptoms of depersonalization and derealisation, where the self and world are drained of subjective reality (the opposite of ecstatic perceptual vividness and enhanced self-awareness). Anatomically the anterior insula is among the most highly developed brain regions in humans when compared to other animals, and it even houses a special kind of ‘Von Economo’ neuron. These and other findings are motivating new research, including experiments here at the Sackler Centre for Consciousness Science, which aim to further illuminate the role of the insula in the weaving the fabric of our experienced self. The finding that electrical stimulation of the insular can lead to ecstatic experiences and enhanced self-awareness provides an important advance in this direction.

Picard’s work brings renewed scientific attention to the richness of human experience, the positive as well as the negative, the spiritual as well as the mundane. The finding that ecstatic experiences can be induced by direct brain stimulation may seem both fascinating and troubling, but taking a scientific approach does not imply reducing these phenomena to the buzzing of neurons. Quite the opposite: our sense of wonder should be increased by perceiving connections between the peaks and troughs of our emotional lives and the intricate neural conversations on which they, at least partly, depend.

Interoceptive inference, emotion, and the embodied self

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ImageSince this is a new blog, forgive a bit of a catch up.  This is about a recent Trends Cognitive Sciences opinion article I wrote, applying the framework of predictive processing/coding to interoception, emotion, and the experience of body ownership.  There’s a lot of interest at the moment in understanding how interoception (the sense of the internal state of the body) and exteroception (everything else) interact.  Hopefully this will contribute in some way.  The full paper is here.

Interoceptive inference, emotion, and the embodied self

ABSTRACT:  The concept of the brain as a prediction machine has enjoyed a resurgence in the context of the Bayesian brain and predictive coding approaches within cognitive science. To date, this perspective has been applied primarily to exteroceptive perception (e.g., vision, audition), and action. Here, I describe a predictive, inferential perspective on interoception: ‘interoceptive inference’ conceives of subjective feeling states (emotions) as arising from actively-inferred generative (predictive) models of the causes of interoceptive afferents. The model generalizes ‘appraisal’ theories that view emotions as emerging from cognitive evaluations of physiological changes, and it sheds new light on the neurocognitive mechanisms that underlie the experience of body ownership and conscious selfhood in health and in neuropsychiatric illness.

As always, a pre-copy-edited version is here.

Predictive processing, sensorimotor theory, and perceptual presence

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I have a new ‘Discussion’ paper just out in the journal Cognitive Neuroscience. Right now there is just the target paper – eventually it will appear with published commentaries and my response.  The basic idea is to bring together, in a formal theoretical framework, ideas from Bayesian predictive processing and ‘enactive’ sensorimotor theory.  The new theory explains ‘perceptual presence’ in terms of the counterfactual richness of predictive representations, and it can also explain the absence of such presence in important cases like synaesthesia.

A predictive processing theory of sensorimotor contingencies: Explaining the puzzle of perceptual presence and its absence in synaesthesia

(A pre-copy-edit version can be obtained here)

ABSTRACT: Normal perception involves experiencing objects within perceptual scenes as real, as existing in the world. This property of “perceptual presence” has motivated “sensorimotor theories” which understand perception to involve the mastery of sensorimotor contingencies. However, the mechanistic basis of sensorimotor contingencies and their mastery has remained unclear. Sensorimotor theory also struggles to explain instances of perception, such as synaesthesia, that appear to lack perceptual presence and for which relevant sensorimotor contingencies are difficult to identify. On alternative “predictive processing” theories, perceptual content emerges from probabilistic inference on the external causes of sensory signals, however this view has addressed neither the problem of perceptual presence nor synaesthesia. Here, I describe a theory of predictive perception of sensorimotor contingencies which (i) accounts for perceptual presence in normal perception, as well as its absence in synaesthesia, and (ii) operationalizes the notion of sensorimotor contingencies and their mastery. The core idea is that generative models underlying perception incorporate explicitly counterfactual elements related to how sensory inputs would change on the basis of a broad repertoire of possible actions, even if those actions are not performed. These “counterfactually-rich” generative models encode sensorimotor contingencies related to repertoires of sensorimotor dependencies, with counterfactual richness determining the degree of perceptual presence associated with a stimulus. While the generative models underlying normal perception are typically counterfactually rich (reflecting a large repertoire of possible sensorimotor dependencies), those underlying synaesthetic concurrents are hypothesized to be counterfactually poor. In addition to accounting for the phenomenology of synaesthesia, the theory naturally accommodates phenomenological differences between a range of experiential states including dreaming, hallucination, and the like. It may also lead to a new view of the (in)determinacy of normal perception.

Bhola Nath Seth: Nov 1st 1927 – June 21st 2013

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My father, Bhola Seth, who has died aged 85 was a gentle and dignified man who arrived in Britain from his native Allahabad on Guy Fawkes night, 1947. Although he settled in rural Oxfordshire he remained devoted to his Indian roots and his ashes will return half to the river Ganges, the other half to his beloved Lake District.

Born in November 1927 to Basudewa Seth – a lawyer of very regular habits – and his wife Dhanno Bibi, Bhola was one of seven children, just three of whom survived to adulthood. As part of an extended family he had a happy childhood and he excelled at badminton, at one point reaching the top 10 or 15 within India. He received a B.Sc. from Allahabad University in 1945 and two years later, amidst the tumult of India’s partition, he left for Cardiff to study engineering.

Known from then on simply as Seth, he spent three years in Cardiff and a further three in Rugby at the English Electric Co. before moving to Sheffield, where he studied for a Ph.D. in mechanical engineering. It was there he met Ann Delaney, daughter of a working-class Yorkshire family, whom he married in 1960 at a time when mixed-race marriages were unusual. In 1961 they moved south so that Seth could take a job at the Esso Research Centre near Abingdon, where he enjoyed working until his retirement in 1992. He remained a keen badminton player, winning the veterans world doubles title in 1976. He also became increasingly fond of the mountains of the Lake District having been introduced to them by Ann early in their relationship. As recently as 2005 together they climbed 70 separate “Wainwrights”.

As he aged, my father’s thoughts turned increasingly towards his family in India, for whom he had long been the patriarch. He made his final trip there in November last year after which his health started to fail. In the final week of his life, my mother and I were overwhelmed by the generosity, dedication, and support provided by the Marie Curie foundation, Hospital at Home, and all the wonderful carers, nurses, and doctors of the NHS who together allowed him to die peacefully and comfortably at home, as was his wish. We hear too little about these heroes of public service.

He is survived by his wife Ann, by his younger brother Amar and his family, and by me, his son Anil.

Note: This article first appeared in the Other Lives section of The Guardian, on July 3rd 2013.

Near-death experiences: The brain’s last hurrah

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Brain scan MRI

We have all wondered what it will be like to die, and what – if anything – might happen afterwards. The prospect of no longer existing seems so difficult to accept that cultures throughout history have developed spiritual and religious beliefs about the persistence of consciousness after the body’s physical demise. Back in the 17th Century, Rene Descartes famously proposed that ‘mind stuff’ (res cogitans) has a separate form of existence from ‘material stuff’ (res extensa), thus introducing the thorny problem of how they might interact, and whether one might exist without the other.

Beliefs about persisting consciousness have been reinforced by reports of unusual ‘near death experiences’ which often involve the feeling that the soul has left the body and is approaching another reality characterized by bright light and blissful feelings. Now neuroscience has got in on the act, with a remarkable study by Jimo Borjigin and colleagues from the University of Michigan showing a transient surge in brain activity after the heart stops.

Most neuroscientists would be very sceptical of claims that consciousness of any sort could exist independently of a living brain. There is a growing consensus that consciousness, like life, weather, and cricket, is just another part of the natural world – albeit one that is reluctant to divulge its secrets. But it is unwise to dismiss reports of near-death experiences, which are usually reported after traumatic life-threatening events like heart attacks. What’s impressive is that these experiences are very consistent across individuals and even across cultures. I take this to mean that the people actually do have the experiences they say they have.

The challenge for science is to explain how the brain can generate these kinds of unusual experiences without assuming that consciousness can exist independently of the brain. Take the related phenomenon of ‘out of body experiences’, in which people experience themselves as being spatially separated from their body. The fact that people reliably report these events (sometimes as part of near-death experiences) does not mean their conscious self must literally leave their body to float around somewhere near the ceiling. We now know that similar experiences can be induced by electrically stimulating particular parts of the brain, or even by the clever use of virtual reality technology.

Some estimates suggest that up to 1 in 5 cardiac arrest survivors have near-death experiences, and given the traumatic contexts in which they occur it’s not surprising that they are sometimes interpreted as ‘proof’ of heaven or of some sort of afterlife. In reality, though, all aspects of these experiences can likely be explained just in terms of normal brain functions gone awry. Out-of-body experiences depend on the brain making the best guess of where its body is, based on sensory inputs. The so-called “tunnel of light” is not a stairway to heaven: it is probably caused by reduced blood flow to the retina and visual cortex (as occurs at high G-forces for test pilots). Abnormal activation of different brain regions, similar to what happens when dreaming, could account for re-experienced memories. Even strange phenomena like an awareness of being dead or seeing other apparently dead people can be related to similar delusions and hallucinations in other clinical conditions.

Despite all this, little has been known about what happens in the brain immediately after the heart stops beating. To address this, Borjigin’s team induced heart attacks in anesthetized rats and, surprisingly, found that brain activity continued after cardiac arrest, with some features actually becoming more prominent in the subsequent 30 seconds. Although these results are from rats and (fortunately) not people, they suggest the brain may have a final electrical ‘hurrah’ as it shuts down. If the same thing happens in humans, it might account for some other aspects of near-death experiences, like heightened alertness.

Looking ahead, the Michigan team’s work lays new foundations for a deeper scientific understanding of the unusual changes in the brain that accompany some of our more remarkable experiences. It also underlines that death is not an event but rather a process, something I became personally aware of while sitting with my father as he died earlier this year.

What is it like to die? We still don’t know, but now there is even less reason to invoke the paranormal, supernatural, or theological in shaping an explanation. And to me this only increases the wonder of life and of all the experiences it holds, even as it comes to an end.

Note:  This post first appeared in The Guardian on Aug 15, 2013.