Posts tagged consciousness

Self-reflective Consciousness and Existential Concerns

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I am currently reading ‘A life worth living‘ and found the introductory chapter by Mihaly Csikszentmihalyi quite stimulating and inspiring.

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In that chapter, Mihaly claims that human brains are unique in lieu of their ability to give rise to self-reflective consciousness (I believe that many primates and some other animals may also have self-reflective consciousness, but that is tangential to our discussion here).  This self-reflective consciousness in turn leads to some interesting psychological effects.

To begin with, the self-reflective consciousness gives rise to a sense of individuality– a sense that one is an individual separate from the nature/ environment. This sense of individuality leads to an anxiety about death. In Mihaly’s own words:

Selfishness and cruelty, which formerly existed mainly as tools for biological survival, now have become extended to protect the psychological needs of the self, for the metabrain cannot help but conclude that its own existence is the most precious thing in the world, and all other goals pale in importance compared to its preservation. The terror of nonexistence, the fear of death, has become one of the ruling motives of humans.

This fear and reality of death is one of the first and foremost existential concern. The second concern that one typically encounters in existential texts is the fear and reality of freedom or choices. Again in Mihaly’s words:

Paradoxically, self-reflection also ushers in the possibility of self-doubt. As humans realized that they were independent individuals with a short lifespan, the question of what choices would lead to a meaningful life became increasingly urgent.

The third reality and fear of isolation is also apparent from the dawning of self-reflective consciousness and a sense of individuality.

The realization of individuality brought about a sense of isolation and finitude, but it also gave the impression of autonomy and freedom.

For understanding the last existential reality and fear of meaninglessness, we need to understand how self-reflective consciousness makes us question the implicit meaning of living and makes us seek for external frames of meaning. For an (non self-reflective) animal, the question of whether life is worth living simply does not arise.

After all, if the spark of consciousness only lasts a few heartbeats in the cosmic darkness, is there really any point in hanging on to life, when so much of it involves suffering? To answer this question, our ancestors—freed and unmoored from the implicit meaning provided by biological existence—had to come up with credible reasons that life was indeed worth living. The myths, religions, and philosophies of every culture have been in large part directed toward answering that question.

With science and reductionist thinking eating up on any semblance of meaning we may derive from earlier systems like myth, religion etc its imperative to ground meaning in new secular and non-mystical terms.

I am sure when Mihaly was writing these paragraphs, existential thinking was not on top of his mind, but isn’t it great to see how even in early days existential thinking and concerns were coupled with a positive psychology focus and PP2.0 is not all that new!

Dreaming as delirium, protoconsciousness or epiphenomenon?

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J Allan Hobson, has never shied form  making bold departures from existing trends when it comes to dream research. At the time when Freudian notions of dream interpretation and dreams-as wish-fulfillment were at it speak, he proposed a theory that dreaming or the subjective state be distinguished from the underlying REM sleep physiological brain state and that dreaming or subjective experience thereof may be an epiphenomenon associated with the underlying physiology. In other words REM sleep may have a function, but the dream state accompanying it is just an epiphenomenon- our minds trying to make sense of random internally generated signals, in the absence of signals from the external world.

In between Hobson has written a book titled Dreaming as Delirium, in which he compares dream state to that of the psychotic state,  especially the delirium accompanying such psychotic states. while dream sttes are naturally cut-off from reality ( no sense inputs or motor outputs) , psychosis, that is indeed characterized by lack of contact with reality, may also thus be predominantly  internally generated and close to the dream state in its characterization.

In his most recent review paper in Nature reviews Neuroscience , he compares the dream state to that of proto consciousness. As per him, proto consciousness is made up of raw emotions and perceptions while secondary consciousness is made up of awareness about perceptions and emotions and meta cognitive processes. He now endows dreams/REM state with some functional significance. He believes that dreams provide and opportunity for inbuilt genetic scripts and schema to be played out and fine tuned against external real-world scenarios. In this view dreams would still be significant as they provide a window to out internal scripts that are present from birth. He doesn’t put this across in so many words and this is my interpretation, but that is what I could sort of intuit.  You are encouraged to read the original paper which is relatively much more accessible as compared to his 1977 paper.

While some people even deny any function to consciousness and call it an epiphenomenon, and thus it would be very hard to convince them of any significance to the bizarreness of dreams; yet I believe that Dreams , not of the garden variety type, but those that we ourselves consider significant, do have a significance and are not mere epiphenomenon. It may be akin to everyday consciousness not having any major role than that of post-hoc narrative weaving; but at some time free will does assert itself and conscious will rules at some rare occasions.  So not all dreams are created equal, some indeed are more than epiphenomenon.  They may be delirium like in nature but perhaps tend towards more of hyper consciousness than proto consciousness.

Hat tip: Neuroskeptic

Hobson, J. (2009). REM sleep and dreaming: towards a theory of protoconsciousness Nature Reviews Neuroscience, 10 (11), 803-813 DOI: 10.1038/nrn2716

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Neural correlates of conscious access: implications for autism/psychosis

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There is a recent article in New Scientist about consciousness and its neural correlates and the article focuses on work of Stanislas Deheane and his colleagues and how they are trying to get evidence and proof for the Global workspace theory of consciousness as proposed by Beranrd Baars.

That led me to this excellent article by Raphaël Gaillard that uses iEEG (intracranial EEG) using electrodes placed in brain, but not doing single-cell recording but still working on aggregates but at a much higher spatial and temporal resolution than normal extra-cranial EEG. They used electrodes placed in epileptic patients undergoing surgery and determined the difference in neural activity during conscious and unconscious access.

For differentiating between the unconscious and conscious access they used the popular visual masking paradigm, whereby a target word is presented and then immediately afterwords (after a few ms only) a mask is presented; if the duration of stimuli presentation is less and it is immediately followed by a mask, then though the stimulus is processed unconsciously, it is not available for verbal report and is not processed consciously. In contrast, in the unmasked condition, the target is not followed by a mask and hence is available for conscious access. In the present experiment, the authors used a forward as well as a backward mask and also had a condition whereby a blank screen was present instead of target ; so that effects of processing target alone could be determined after subtracting the effect of masks. the paper is one access and very lucidly written so go have a look!

A quick detour: Bernard Baars global workspace theory posits that consciousness arises when neural representations of external stimuli, are made available wide spread to global areas of the brain and not restricted to the originating local areas. This has also been characterized as an attentional spotlight and whatever comes under the spotlight in global workspace, is widely visible to the rest of the audience (the other parts of the brain) and also gives rise to consciousness. In the absence of coming to focal awareness(spotlight), the processing/representation happens unconsciously by the many different parallel brain modules. Thus, while unconscious representations may arise in brain locally, to become conscious they need to become widespread and available to the entire (or most of) the brain. To boot:

We adopted a theory-driven approach, trying to test experimentally a set of explicit predictions derived from the global workspace model of conscious access. This model, in part inspired from Bernard Baars’ theory [30], proposes that at any given time, many modular cerebral networks are active in parallel and process information in an unconscious manner [22,23,31,32]. Incoming visual information becomes conscious, however, if and only if the three following conditions are met [23]: Condition 1: information must be explicitly represented by the neuronal firing of perceptual networks located in visual cortical areas coding for the specific features of the conscious percept. Condition 2: this neuronal representation must reach a minimal threshold of duration and intensity necessary for access to a second stage of processing, associated with a distributed cortical network involved in particular parietal and prefrontal cortices. Condition 3: through joint bottom-up propagation and top-down attentional amplification, the ensuing brain-scale neural assembly must “ignite” into a self-sustained reverberant state of coherent activity that involves many neurons distributed throughout the brain.

Based on this theoretical framework, the following hypothesis were developed:

Neurophysiological Predictions Derived from the Global Workspace Model

In the light of our model, the masked–unmasked contrast corresponds to a comparison between a visual representation satisfying only condition 1 and a representation satisfying all three conditions for conscious access listed above. The global workspace model therefore leads to the following four predictions.

Prediction 1: a common early stage of processing.
Both masked and unmasked words should evoke similar neural activity within an early time window, reflecting a fast feedforward sweep propagating from posterior to anterior cortices. In particular, invisible masked words should induce transient event-related responses along the ventral visual pathway, as assessed by iERPs and ERSP.

Prediction 2: a temporal divergence.
Following this initial common stage, only unmasked words should be associated with sustained effects. We thus predict a divergence in cortical activation for unmasked and masked words. Given that we contrasted heavily masked stimuli with unmasked stimuli, we expect a progressive buildup of the divergence between these two conditions. In the light of recent high-resolution scalp electroencephalogram (EEG) studies in visual masking and attentional blink paradigms, this temporal divergence is expected to occur within a 200–500-ms window [1,2].

Prediction 3: an anatomical divergence.
The activation of frontal and parietal areas, which are allegedly dense in global workspace neurons, should be particularly sensitive to consciously perceived words (see [32] and Figure 1 of [22] for explicit simulations of this property). Although masked words may cause a small, transient and local activation within these regions, we predict that unmasked words should elicit a global and long-lasting activation of these regions, corresponding to a broadcasting process.

Prediction 4: phase synchrony and causality.
During this late time window, the long-lasting and long-distance neuronal assembly specific to conscious processing should be associated with an intense increase in bidirectional interelectrode communication. Measures of phase synchrony and Granger causality should be particularly apt at capturing this phenomenon.

And this is exactly what they found. They found that upto 200 ms activity in the unmasked and masked condition did not differ significantly and represented an early stage of processing. In the 200-500 ms window (post stimulus onset), there was temporal divergence with there being long-distance beta synchrony, sustained amplitudes and power in gamma band and Granger causality in the unmasked case, but not in the masked case. Further, there was anatomical divergence, with the unmasked condition showing more occipitotemporal activation, while the unmasked condition showing global (and especially frontal) activation. Lastly while local beta synchrony and reverse feed back causality (accounted perhaps by top-down attentional factors that try to focus more given the masking) was associated with the masked condition, long distance beta synchrony and causal imbalance in the feed-forward direction was only found in the unmasked condition, thereby validating the claim that in the unmasked condition the posterior local representations weer made globally available to anterior regions as well (these are my very brief summaries, you should read the original freely available article for nuances and details).

This is how the authors conclude:

The main motivation of our study was to probe the convergence of multiple neurophysiological measures of brain activity in order to define candidate neural signatures of conscious access. Conscious word processing was associated with the following four markers: (1) sustained iERPs within a late time window (>300 ms after stimulus presentation); (2) sustained and late spectral power changes, combining a high-gamma increase, beta suppression, and alpha blockage; (3) sustained and late increases in long-range phase coherence in the beta range; and (4) sustained and late increases in long-range causal relations.

Our results suggest that in the search for neural correlates of consciousness, time-domain, frequency-domain, and causality-based electrophysiological measures should not be seen as competing possibilities. Rather, all of these measures may provide distinct glimpses into the same distributed state of long-distance reverberation. Indeed, it seems to be the convergence of these measures in a late time window, rather than the mere presence of any single one of them, that best characterizes conscious trials.

That brings me back to the new scientist article:

Dehaene’s group had already shown that distant areas of the brain are connected to each other and, importantly, that these connections are especially dense in the prefrontal, cingulate and parietal regions of the cortex, which are involved in processes like planning and reasoning.

Considering Baars’s theory, the team suggested that these long-distance connections may be the architecture that links the many separate regions together during conscious experience. “So, you may have multiple local processes, but a single global conscious state,” says Dehaene. If so, the areas with especially dense connections would be prime candidates for key regions in the global workspace.

Now it is well known that in autism there are more local connections and more local processing; while psychosis/ schizophrenia spectrum is marked by more long-distance connections/ activity. If so , it is not unreasonable to conclude that psychotics may have higher p-conscious experiences while autistics may be stuck at more lower A-conscious experiences. I proposed something like that in my post titled ‘what it is like to be a zombie‘ and you are strongly encouraged to go read it now.

Further we also know that default mode network is highly activated in psychosis and very less in activity in autistics and that is again converging proof. From the new scientist article:

Certain regions of the brain’s global workspace, dubbed the default mode network (DMN), are active even when we are resting and not concentrating on any particular task. If the global workspace really is essential for conscious perception, Laureys’s team predicted that the activity of the DMN should be greatest in healthy volunteers and in people with locked-in-syndrome, who are conscious but can only move their eyes, and much less active in minimally conscious patients. Those in a vegetative state or in a coma should have even less activity in the DMN.

The researchers found just that when they scanned the brains of 14 people with brain damage and 14 healthy volunteers using fMRI. In a paper published in December 2009, they showed that the activity of the DMN dropped exponentially starting with healthy volunteers right down to those in a vegetative state (Brain, vol 133, p 161). “The difference between minimally conscious and vegetative state is not easy to make on the bedside and four times out of 10 we may get it wrong,” he says. “So this could be of diagnostic value.”

While the DMN may be important marker for brain damaged patients, it also has the potential to become a marker for different feels of consciousness sin brain intact but differently wired brains like those of autistics and psychotics.

I believe one way of conceptualizing autism is as a diminishing of consciousness/ subjective experience; while that of psychosis as overabundance of consciousness/ subjective feeling. Maybe that is why shamans of all ages have been closely identified with the psychotic spectrum.

If autistics have more local processing, then perhaps they should be better at tasks involving unconscious stimuli: perhaps that’s why despite their savantic abilities , much of what happens in the autistic mind is not only non-verbal , but also non-conscious and hence not juts not available for verbal report, but not accessible to consciousness.

I strongly feel that adding the consciousness dimension to autism/schizophrenia spectrum may be a good thing and lead to more clarity and new directions in research.

Gaillard, R., Dehaene, S., Adam, C., Clémenceau, S., Hasboun, D., Baulac, M., Cohen, L., & Naccache, L. (2009). Converging Intracranial Markers of Conscious Access PLoS Biology, 7 (3) DOI: 10.1371/journal.pbio.1000061

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