Saturday, December 13, 2008

Consciousness update

A recent scientific review lays out what is known about consciousness.

With convenient timeliness, Science magazine published a lengthy review of the state of consciousness research, within a standout issue devoted to behavioral genetics. Unfortunately, the review begins: "How consciousness arises from the brain remains unknown". Nevertheless the basic analytic approach of investigating variations in a phenomenon upon perturbation has yielded a wealth of clues about how the mind happens. I will use "mind" to denote the subjective experience which has been so difficult to explain scientifically and philosophically.

Minds turn off during deep sleep, then back on during dream sleep and during waking. They turn off again during the super-activation of epileptic seizures. The mental on state correlates with the complexity of brain wave (EEG) patterns, where deep sleep is characterized by a low complexity pattern (delta wave) of slow and regular on, off alternating at four cycles per second or less. This state also appears to be the default state of the cortex, when in a coma or when otherwise lacking the activating functions of the reticular activating system in the brain stem. Waking is a noisy condition with jumbled, higher-frequency waves (15 to 40 cycles per second- gamma waves), and then epilepsy is characterized by everything firing at once- again a low complexity state. Many variations on these states are achievable by drugs, whether professionally or recreationally applied. Many more variations appear after physical damage, such as from strokes, trauma, neurosurgery, etc.

It looks like brain waves are somewhat like the cloud of radio waves from radio stations, where signal complexity is a sign of information, and a repetitive test signal, or flat-lining, or hyperactive noise, are each degradations of that signal- a loss of information. If we knew how to decipher the signals, would we be able to peek into someone's mind? It is not at all clear that they would be decipherable in that way. The broadcast nature of brainwaves, while convenient for us to measure on the scalp, is not their real role- the EEG signal is merely a messy side-effect of activity in the many neurons going back and forth between specific locations in the brain.

It is in the rapid signaling between a large number of specific places where one would have to look for correlates of the mind. Indeed the leading theory regards complex waking gamma-wave states as reflections of transient coalitions of active brain regions, bound together in cleverly time-compressed neuronal gamma-pattern firing (the actual neuronal firings, not the waves we detect on the scalp). This is suggested by Gyorgy Buzsaki in his magisterial review of brain waves (especially Cycle 9: The gamma buzz: gluing by oscillations in the waking brain, which addresses the binding problem of consciousness). In this way, anatomical localization of activity, which is very well characterized by now, (another article in this issue uses fMRI scans of subject brains to peek into and predict speech and speaker identification to a remarkably accurate degree, based on location of brain activity ), could be melded together into what we experience as a unitary mind.

Anatomically, regions of the brain are involved in consciousness to various degrees. Small lesions in the thalamus can induce immediate coma, whereas frontal lobotomies have much less effect, and lesions in the cerebellum little to none. This review argues very plausibly that the middle region of the brain, comprising medial cortex on the outer brain, and thalamic core below it, serves as a sort of central nexus in terms of connectivity of the brain, and likewise has the most central role in consciousness. For instance, the visual processing system is arranged hierarchically from V1 to V5, where V1 is most closely connected to input from the retinas (firing with and representing simple features of the visual scene, such as light at a specific coordinate), and never contributes to consciousness directly, while the neurons in V5 represent complex aspects that do enter consciousness directly, like the identity of objects and faces. The orientation of the visual cortex places the V1 areas at the back of the head and V5 areas closest to the middle mind-relevant features mentioned above.

The review also promotes a rather vague theory about information and complexity, where data integration over large regions (roughly measured by brain waves), and discrimination between many alternative states, is the key measure of any process that can be called consciousness. For instance, transcranial magnetic stimulation (TMS) can be used to directly activate brain regions. If this is done on someone deep in deep non-REM sleep, the result is a localized and brief low-frequency wave. In contrast, TMS on the waking brain stimulates complex wave responses that propagate far and wide through the rest of the brain, resounding for twice as much time. The paper does not relate what thoughts TMS induces in waking subjects, but other studies indicate that it induces flashes of light or other random perceptions depending on what region of the brain is being stimulated, similar to what is generated by migraines. So, though there are more and less relevant areas of the brain, consciousness still seems to be a distributed phenomenon, as indeed one might guess from the vast amount of information it subjectively integrates.

This is all of special interest to anesthesiologists, who are in charge of managing body control, pain, and consciousness. The review mentions many variations that can occur- patients that suddenly wake up during anesthesia, low doses of anesthetics that induce out-of-body experiences and depersonalization, low doses that generate amnesia and unresponsiveness despite consciousness still being present in some form. The immediate problem is that there are currently no perfect measures of consciousness per se, and anesthesiologists are naturally anxious to have one. What everyone is sure of, however, is that when brain waves cease entirely, the patient is dead- to the world, if not permanently.

Another clear conclusion is that consciousness is graded- that we can, under the influence of brain damage, exotic drugs, or just plain alcohol or sleepiness, experience vastly different amounts of consciousness. Indeed, we love exploring these altered states, consuming coffee, coca, chocolate, or riding in roller coasters for stimulation, while taking heroin, alcohol, barbiturates, or meditating for tranquilization (among many other options, like marijuana and LSD). Each of these variations are clearly connected to physical alterations in the brain. The graded-ness of consciousness has significant implications, especially for the moral status of other conscious beings. Obviously, animals such as dogs experience consciousness- perhaps not quite as exquisitely as we do, but richly nonetheless, especially in the smell department. Thus there is a graded order of beings that deserve our sensitive attention due to their consciousness, especially their capacity for conscious suffering. Conversely, human embryos are not conscious, and nor are fetuses up to some mid-stage in gestation (roughly five months), which informs our moral duties towards them as independent, conscious beings.

In view of all these detailed connections between mind, consciousness, and the brain, it should be exceedingly difficult to imagine that consciousness can exist in any form after death. Putting another nail in the coffin, as it were, will be a study that tests the hypothesis that out-of-body (or near-death) experiences reflect separation from the body. Operating rooms have been set up with upward-facing images on high shelves- items that would only be visible to someone floating above. Patients who have out-of-body experiences will then be asked about these, which will test whether their sensory selves are floating as they subjectively appear to, or whether they are strictly confined to the operating table- to what they can hear and what they have seen, either before or after the operation. We will see. My bet is that our sense of hearing is extremely sensitive and capable of painting a rich picture of what is going on outside, accounting for the various anecdotal accounts of uncanny perception while having out-of-body sensations, much like it does in half-asleep states.



All this presents a further question- if consciousness is eventually nailed down to brain functions, as it seems certain to be, does that present any philosophical problems, either for free will or for the efficacy of reason? For free will, how can we be truly free in our choices if our mind is strictly subject to material cause and effect? And similarly for reason, how can our reason be an impartial judge and guide if it arises from such an inherently compromised and contingent substrate as the brain?

In the first place, our free will is a good deal less free than we suppose, as advertisers and tobacco companies know so well. We are influenced all the time, thus the desperation of theists to maintain their influence. Secondly, our conscious ignorance of most influences (in addition to a big helping of randomness in the system) amounts to free will- a will that has no obvious origin and which makes decisions based on reason, or impulse, or whatever happens to come to mind. That can make psychological investigations threatening. If we expose reasons for our heretofore "free" actions, whether cast in the languages of complexes, archetypes, psychodynamics, parental influences, memes, consumerism, etc., we are less "free" insofar as these interpretations are true. Nothing has changed, but our view of ourselves is altered, and we may become more "self-conscious", which means ... more suspicious about our so-called free will.

This may be one of the deeper reasons for theist antipathy towards knowledge in general, which one might see as impairing our natural, reflexive engagement with the world (not to mention religious authority). Whether it is the knowledge given by the fruit of the tree of life, carnal knowledge, critical historical knowledge of their own texts, biological knowledge, or psychological self-knowledge, this hostility is quite remarkable. Scientologists take the prize in this last department for quite understandable reasons with their vitriolic campaign against psychology, while they simultaneously peddle their own pseudo-psychology of "clearing" and dianetics.

So is reason itself futile? If thoughts all have causes, many of them less than noble, let alone free of outside influence, how can reason operate at all? I think one can ask the same of a hand-held calculator. Does it provide reliable answers, despite its inner workings being fully understood? At best, human reason is a similarly general tool, which we can apply to any problem, and, given sufficient discipline, get robust answers from. Such is the case with mathematical proofs, where all steps can be written down, going their leisurely way from premises to conclusions. In more nebulous realms such as philosophy and ethics, each step is fraught with subjective interpretations, so the framework of reason is less in evidence, if it is present at all. It falls to critics to make that framework and its defects or successes as explicit as possible. The success of science has hinged on making its reasoning about the natural world as explicit and open as possible, thereby making useful critique possible, especially in the form of the acid tests of reality- experiment and evidence.



Incidental links:
  • Related podcast on Hume and reason.
  • Podcast on blind sight, phantom limbs, alien hands, body sense, mirror neurons, and extra senses, in a philosophical context.
  • Death of HM, the man who had complete amnesia due to damage to his hippocampus.

Even more incidentally, we happen to be getting to the end of War and Peace, where, on the very last page, Leo Tolstoy makes essentially the same argument about free will as I make above (translation by Rosemary Edmonds):
As with astronomy the difficulty in the way of recognizing that the earth moves consisted in having to rid oneself of the immediate sensation that the earth was stationary accompanied by a similar sense of the planets' motion, so in history the obstacle in the way of recognizing the subjection of the individual to the laws of space and time and causality lies in the difficulty of renouncing one's personal impression of being independent of those laws. But as in astronomy the new view said: "True, we are not conscious of the movement of the earth but if we were to allow that it is stationary we should arrive at an absurdity, whereas if we admit motion (which we do not feel) we arrive at laws", likewise in history the new theory says: "True, we are not conscious of our dependence but if we are to allow that we are free we arrive at an absurdity, whereas by admitting our dependence on the external world, on time and on causality we arrive at laws."

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