Field theories of consciousness
|Susan Pockett (2013), Scholarpedia, 8(12):4951.||doi:10.4249/scholarpedia.4951||revision #137909 [link to/cite this article]|
The field theories of consciousness discussed in this article are theories of the nature of consciousness, in which consciousness is conceived as being identical with a field in the general sense in which the term ‘field’ is used in physics. This means that in these theories, consciousness is seen as having not only duration, but also extension in space. In most of the theories discussed, consciousness is proposed to be identical with some aspect of a physical field i.e. a field in which the property that exists at each point in a particular region of the spacetime continuum is objectively measurable. However, in at least one of the theories, consciousness is proposed to be identical with a hypothetical non-physical field, which nevertheless still has extension in space. This article does not discuss the variety of sociological theories of consciousness stemming from the work of Kurt Lewin, in which the word ‘field’ is taken to mean an abstract entity that includes not only each individual’s conscious thoughts, emotions and desires, but also the various external and internal forces acting upon these.
The field theories of consciousness that are discussed in this article can be further subdivided into two varieties, depending on the meaning of the word ‘consciousness’. For most of human history, the word ‘consciousness’ was generally taken to indicate not the sort of individual awareness to which the word now refers, but rather a universal entity variously named Atman, Brahman, Allah, Jehovah, God, the Unmoved Mover (Aristotle), Absolute Spirit (Hegel), or any number of other names according to who was writing about it. However, during the late 19th century and all of the 20th century, Charles Darwin’s mechanistic explanation of how the biota of the world came to have their present form largely supplanted theistic creation stories, to the extent that by the early 21st century any discussion of a hypothetical global consciousness has become more or less taboo in academic circles. Hence a brief history of philosophical treatments of global consciousness and some recent attempts at experimental investigation of the matter are relegated to a sub-article called Field theories of global consciousness.
The remainder of the present article deals exclusively with scientific field theories concerning the everyday conscious experiences of individuals, including the basic sensations sometimes known as qualia (colours, sounds, smells, tastes, various kinds of touch or somatosensation). Three such theories are described and discussed, in chronological order.
Köhler’s field theory
It is widely believed (e.g. Rose, 2006) that in the 1930s and 40s the Gestalt theorist Wolfgang Köhler put forward an electric field theory of consciousness, which was tested and disproved by Karl Lashley and Roger Sperry in the early 1950s. The truth of the matter is somewhat different.
First of all, Köhler did put forward something he called “field theory” (Köhler 1940), but he never once used the word ‘consciousness’ in his written work, and never explicitly proposed that there might be identity between brain-generated electric fields and conscious sensations. Köhler only ever referred to electric fields as cortical correlates of percepts. His field theory was a theory of brain function.
Secondly, Lashley’s test of what he claimed was Köhler’s theory (Lashley et al 1951) actually did not adequately test even Köhler’s theory, let alone the modern electromagnetic field theory of consciousness as outlined later in this article. Lashley’s test was to lay several gold strips across the entire surface of one monkey’s brain, and insert about a dozen gold pins into a rather small area of each hemispheric visual cortex of another monkey. The idea was that these strips or pins should short-circuit the hypothesized figure currents, and thereby (if Köhler’s field theory was correct) disrupt the monkeys’ visual perception. Lashley did no tests to see whether his inserts actually did disrupt any vision-related currents in the brain, but simply performed one test of each monkey’s post-operative vision, by asking the monkey to use its pre-operation training to distinguish between 4 pairs of visual patterns on plates covering dishes that did or did not contain food. The monkeys performed about as well on this task after insertion of the pins or strips as they had before (although the one with the inserted pins did “occasionally fail to see a small bit of food in the cup”) and Lashley felt justified in concluding from this that “the action of electric currents, as postulated by field theory, is not an important factor in cerebral integration.” Later Roger Sperry (Sperry et al 1955) did experiments similar to Lashley’s, making sub-pial cuts and implanting tantalum pins into cat brains and reporting similarly negative results (but wisely remaining more circumspect about their interpretation). In fact the security of Lashley’s conclusion is highly questionable, for two reasons:
(a) With the 20:20 hindsight conferred by an extra 70 years of brain research, no present-day neurophysiologist would expect Lashley’s (or Sperry’s) slices, strips and pins to produce any significant changes in the field potentials that modern workers would understand as underpinning Köhler’s hypothesized figure currents. Field potentials are generated by the flow of current into and out of neurons, not across large regions of extracellular space. No major transcortical extracellular current flow such as might be disrupted by the insertion of macroscopic pins features in any modern understanding of brain function.
(b) Lashley believed that the cortex was functionally homogeneous or pluripotential (Lashley 1950), so to him it didn’t much matter where his pins were placed. But modern wisdom is that the cortex is not functionally homogeneous at all, which means that even if Lashley’s inserted pins did disrupt or distort the passage of any hypothetical transcortical river of electric current, it would have been sheer luck if they were positioned in precisely the right place to affect the much more localised figure currents that Köhler actually proposed as being associated with the percepts like those being tested.
Libet’s field theory of consciousness
Like most of his contemporaries, Benjamin Libet swallowed whole Lashley’s anti-Köhler conclusions – but he still liked the idea that consciousness is a field. Therefore Libet proposed in 1994 that consciousness is a field which is “not … in any category of known physical fields, such as electromagnetic, gravitational etc” (Libet 1994). In Libet’s words, his proposed Conscious Mental Field “may be viewed as somewhat analogous to known physical fields … however … the CMF cannot be observed directly by known physical means.”
A field that is not observable directly by known physical means is in some danger of remaining confined to the realms of philosophy, but Libet was able to render his hypothesis scientific by proposing an ingenious experimental test of its predictions. The test involved isolating a slab of cortex known to produce a particular conscious experience so that no synaptic transmission could occur between the interior of the slab and the rest of the brain, then asking whether the conscious experience generated within the slab could still be reported. Libet’s theory predicted that it could, by means of communication between the conscious field generated by the slab and the spatially contiguous larger conscious mental field. The technical difficulties involved with (a) actually doing this experiment and (b) interpreting the results are discussed in detail in Libet’s paper, but remain so formidable that no such experiment has yet been done. However, at this stage it is probably worth pointing out that even if the experiment could be adequately done, the success of Libet’s theoretical prediction in such a test would not distinguish between his theory and the electromagnetic field theory of consciousness as outlined below.
The electromagnetic field theory of consciousness
The central idea of the electromagnetic (EM) field theory of consciousness is that conscious perceptions (and sensations, inasmuch as they can be said to have independent existence) are identical with certain spatiotemporal electromagnetic patterns generated by the normal functioning of waking mammalian brains.
Partly as a result of Lashley’s legacy, this theory struggled for a number of years to achieve publication at all, let alone any degree of acceptance. Susan Pockett started trying to publish it in the Journal of Consciousness Studies in 1995 (Pockett 2002). Around the same time Robert Charman (personal communication) independently submitted essentially the same idea to the same journal, with the same lack of success. Charman then published the idea as a short paper in the ‘alternative’ journal Network (Charman 1997) and withdrew from the fray. Pockett published the essence of the idea as a footnote in a review paper on auditory consciousness (Pockett 1999), worked it up into a book manuscript (which was again rejected by a series of academic publishers) and eventually put the book out using a demand publisher in the year 2000 (Pockett 2000). By this time the idea had been doing the rounds of numerous reviewers for approximately five years and Johnjoe McFadden had written about it in the final chapter of a book about something else (McFadden, 2000). Two years later, the Journal of Consciousness Studies finally accepted the electromagnetic field theory of consciousness as an original contribution from McFadden (2002(a),(b)), Roy John suggested in a more neuroscientific forum that a resonating electromagnetic field might be ‘the embodiment of mind’ (John 2002) and the brothers Fingelkurts proposed a theory that skirted around the central idea of the EM field theory, but included the statement “it is important to stress that we do not attempt to explain how consciousness arises from neuronal tissue” (Finglekurts and Fingelkurts 2002).
During this initial period, a great many objections to the basic idea were advanced in various fora. Refutations of some of these are outlined in section (a) below. Section (b) discusses an apparent controversy between main proponents of the EM field theory about whether or not the proposed conscious electromagnetic patterns can act causally on their own brain – early statements of the theory had it that conscious electromagnetic patterns do have causal actions on the brain (Pockett 2000) or spinal cord (McFadden 2000), but later versions (Pockett 2002; 2011; 2012) questioned the specificity of this effect and pointed out that much if not all of what we intuitively believe to be consciously initiated bodily movement has now been shown to be initiated by pre- or unconscious brain function anyway. Section (c) discusses a recent proposal regarding the detailed constitution of conscious as opposed to unconscious electromagnetic patterns.
(a) Objections to the EM field theory of consciousness answered
The much-raised objection that the EM field theory was disproved by Lashley sixty years ago has already been covered in the section about Köhler’s field theory. Three of the more cogent further objections to the EM field theory of consciousness are discussed below.
(i) Probably the most obvious a priori objection is that common external electromagnetic fields – radio waves, mains voltage, the magnetic fields inside MRI (magnetic resonance imaging) machines – demonstrably have no effect on consciousness. Surely they should, the objection goes, if the electromagnetic field theory of consciousness were correct. MacFadden’s answer to this objection (McFadden 2000) is that the brain is surrounded by a protective Faraday cage of cerebrospinal fluid, which denies entry to external fields. This is easily refuted by the observation that such a Faraday cage would also deny exit to brain-generated fields, which would make it impossible to record EEG (electroencephalograms) from the scalp. Since thousands of research and clinical laboratories around the world routinely record EEG from the scalp every day, the proposed Faraday cage cannot be effective. More plausible refutations of the original objection are that (a) radio waves are of much higher frequency than the proposed conscious fields, so would not be expected to affect their relevant features (b) mains voltage is about the same frequency as the oscillations proposed as being conscious, but electromagnetic oscillations at these frequencies radiate so inefficiently that virtually no power is detectable a few cm from a wall socket (c) the magnetic field inside an MRI machine is powerful enough, but does not have the right spatial configuration to couple with the putative conscious field (as demonstrated by the fact that, once the technical difficulties associated with the recording apparatus are dealt with, the magnetic field generated by MRI machines does not affect EEG recorded within the magnet). But the killer refutation of this objection is essentially a generalization of (c). It is that none of the common ambient EM fields is patterned in the spatial domain. If the inverse spatial pattern of a putatively conscious field pattern were applied externally, the conscious pattern would indeed be cancelled and the conscious experiences represented should be ablated. But if spatially unpatterned external fields are imposed on the brain, the physics of electromagnetism dictates that the putatively conscious field pattern will simply ride up and down on the spatially unpatterned external field, as a boat rides up and down on the waves of an ocean. In the jargon of physics, there will be no coupling between the two fields, so both will continue, unaffected by the presence of the other.
(ii) A second objection to the electromagnetic field theory of consciousness is that experiments with the early ‘split-brain’ patients (in whom the corpus collosum, the fibre tract connecting the two hemispheres of the brain, was cut to prevent spread of epileptic seizures), show that such patients apparently have two separate consciousnesses. The conscious field would (probably) still be unified in split-brain patients, so if, as proposed by the electromagnetic field theory of consciousness, a given subject’s total consciousness is the totality of the conscious field generated by their brain, split brain patients should still have a unified consciousness.
One reasonable answer to this objection is that to the casual observer, split-brain patients do still have a unified consciousness. Even when one does the clever experimental manipulations necessary to demonstrate that in such patients the non-verbal right hemisphere can be made aware of things which cannot be reported by the verbal left hemisphere, it remains true that interhemispheric transfer of information is not entirely absent in commisurotomised subjects. There appear to be two systems, one of which can be split and the other of which cannot (Corballis 1994, 1995). Perhaps the unsplittable system is subserved by the conscious field.
A more cogent refutation of the original objection is as follows. Split-brain patients clearly act in such a way as to indicate that they are aware of events generated by both sides of their brain (as predicted by the EM field theory) - what makes them interesting is simply that they are unable to report this awareness using language. In order for the original objection to hold water, the conscious fields generated by sensory areas (for example) on the non-language-capable side of the brain would need to be able to have a direct effect on neurons in the language areas on the other side of the brain. But as recent versions of the EM field theory (Pockett 2011; 2012) point out, the physics of electromagnetism dictate that the EM dipole patterns constituting putatively conscious fields fall off not merely with the square of distance but actually with the cube of distance from their sources. In other words, conscious EM field patterns are very local. In order for any conscious experience to be reported using language, the conscious field pattern has to act on neurons close to where the pattern is generated and these neurons then have to communicate by standard neurophysiological means (action potentials, synapses and so on) with the language areas. In commisurotomised patients standard neurophysiological communication is physically disrupted, so linguistic reports of conscious experience generated by the non-language hemisphere are impossible.
(iii) A third commonly advanced objection to the electromagnetic field theory of consciousness is that it has no obvious advantages over the widely accepted neural identity theory and therefore should not be adopted. Two answers to this objection are that (a) even if it were true that the electromagnetic field theory of consciousness made no significant predictions over and above those of the psycho-neural identity theory, it is not necessarily true that the first theory to appear is the right one, and (b) in fact the electromagnetic field theory does, in at least one major respect, deliver more than the psycho-neural identity theory ever could. The difference is that the electromagnetic field theory of consciousness predicts that in principle, consciousness could be generated using hardware instead of wetware. This single prediction not only renders the electromagnetic field theory testable where the neural identity theory is not – it also opens wondrous vistas with respect to possible future technologies.
(b) Controversy about possibility of causal action of proposed conscious patterns
The controversy that seems to have developed about whether or not EM fields like those proposed as being conscious can have a causal action on brain function is in this author’s view largely a matter of misunderstanding.
First, it has never been disputed that electromagnetic fields can and do affect neuronal function. Chapter 7 of Pockett (2000) lists a number of circumstances in which brain-generated em fields had already been shown to affect brain function, in areas that probably do not generate consciousness (including the medulla of the gold-fish, the cerebellum and the hippocampus of mammals). McFadden (2013) supplies more recent examples of the demonstrated action of external em fields, both in vitro (mammalian brain slices) and in vivo (the occipital cortex of anaesthetized ferrets). It is thus quite clear that electromagnetic fields absolutely do have the capacity to influence neuronal activity, in both unconscious and (presumably, since nobody suggests that neurons change their biophysical characteristics depending on whether or not consciousness is present) in conscious brain tissue. The fact that em fields can have a direct influence on neuronal function is not now and never has been even slightly contentious.
It is also completely uncontentious that both the generation of EM fields by the brain and the generation of consciousness require synchronous firing of large numbers of chemical synapses on neocortical pyramidal cells. This fact is pointed out on p.95 et seq. of the hard copy version of Pockett (2000), as well as in a number of papers by McFadden (2002a,b; 2006; 2013). The mechanism by which extracellular electromagnetic fields are generated by the synchronous activity of chemical synapses on neocortical pyramidal cells is illustrated diagrammatically in Pockett (2012).
The question in the current context is not whether EM fields like those proposed as being conscious can have a direct influence on neural tissue – clearly they can – or even whether synchrony is necessary for the generation of both consciousness and the putatively conscious EM fields – clearly it is. The question at issue is whether spatial EM patterns like those proposed as being conscious can transfer the information encoded in their spatial patterning back to their own brains in such a way that this information can be the direct cause of specific behaviours. McFadden argues on general grounds that they can. Pockett argues on specific grounds that they can not.
The specific argument put forward by Pockett (2011, 2012) is as follows:
(i) The spatial patterns in question are highly likely to be composed of multiple electric dipoles (each generated by the synchronous action of many synapses on many neocortical pyramidal cells) in a series of adjacent cortical columns (Pockett 2007, 2012). The basic physics of electromagnetism dictates that the strength of the EM field produced by an electric dipole falls off not merely with the square of distance from the source (as for a single electric charge), but with the cube of distance from the source. This means that the EM field encoding a conscious percept is very local. In other words, the spatial EM pattern encoding any given conscious experience is undetectable quite a short distance away from where it was generated.
(ii) This in turn means that putatively conscious EM patterns should be capable of acting as patterns only on the same neurons that generated them. Neurons even slightly further away would simply not “see” these patterns at all.
(iii) Since the neurons directly causing behaviour are in general much too far away from the neurons that generate either sensory experiences or decisions for the patterns generated by the sensory or decision neurons to be “seen” by the neurons causing behaviour, the implication is that if sensory experiences and decisions are spatial EM patterns, consciousness (or at least sensory consciousness and conscious decisions) should not be able directly to cause behaviour. (It could, of course, cause behaviour indirectly, by acting on local neurons which then communicate with the rest of the brain by standard neurophysiological means).
This general argument is potentially damaging if not fatal to the EM field theory of consciousness. If, as we all intuitively believe, our voluntary actions are generated by our conscious thoughts, putatively conscious EM fields should be able to generate actions; preferably directly, although this is really only an aesthetic requirement. It thus becomes important to know whether consciousness (irrespective of what that may turn out to be) does directly cause behaviour.
Counterintuitively, it turns out that a large confluence of evidence has accumulated over the last decade to suggest that largely, it does not (Pockett 2004; 2011; Pockett et al 2006). Even behaviour generally accepted as being voluntary turns out to be initiated unconsciously. As Wegner (2002) concludes, humans interpret their thoughts as the cause of their actions only on the same basis that they interpret anything as the cause of anything else – all that is necessary for A to be interpreted as the cause of B is that A should (a) precede B (by a plausible time chunk) (b) be consistent with B and (c) be the only apparent cause of B.
(c) Proposal on 3-D shape of conscious as opposed to unconscious em patterns
The realization that the initiation of bodily actions is not accessible to consciousness allows a proposal about the 3-D structure distinguishing conscious em patterns from non-conscious em patterns (Pockett 2012). It is now well accepted that sensory consciousness is not generated during the first, feed-forward pass of neural activity from the thalamus through the primary sensory cortex. Recurrent activity from other cortical areas back to the primary or secondary sensory cortex is necessary. Because the feedforward activity goes through architectonic Lamina 4 of the primary sensory cortex (which is composed largely of stellate cells and thus does not generate synaptic dipoles) while recurrent activity operates through synapses on pyramidal cells (which do generate dipoles), the conscious em patterns resulting from recurrent activity in the ‘early’ sensory cortex have a neutral area in the middle of their radial pattern. The common feature of brain areas that can not generate conscious experience – which are now seen to include motor cortex as well as hippocampus, cerebellum and any sub-cortical area – is that they all lack an architectonic Lamina 4. Therefore none of the brain areas that are unable to generate consciousness produces EM fields with a neutral region in the middle of their radial pattern. Thus the feature that distinguishes conscious from unconscious patterns is proposed to be a neutral area corresponding to Lamina 4.
Whether or not this proposal turns out to be correct remains to be seen, but it is certainly an experimentally testable idea, which has the potentially important heuristic feature of pointing out the need to record laminar electromagnetic patterns as well as the more commonly studied micro-column-based patterns tangential to the surface of the brain.
(d) A prediction
The description of the EM field theory of consciousness provided above is incomplete. The theory is about to enter a phase of rapid evolution. Watch this space for updates.
Field theories of global consciousness
This sub-article contains following sections:
- The philosophy of global consciousness: a brief history of God
- Modern field theories of and evidence for global consciousness
- The unified field theory of consciousness
- Other field theories of global consciousness
Charman RA (1997) The field substance of mind – a hypothesis. Network 63, 11-13.
Corballis MC (1994) Perceptual integration following commissurotomy: a reappraisal. In M Sugushita (Ed) New horizons in neuropsychology : proceedings of the 9th Tokyo Metropolitan Institute of Neuroscience (TMIN) Symposium ‘New Horizons in Neuropsychology’, Tokyo, 24-25 November 1993 pp139-158, Elsevier Amsterdam.
Corballis MC (1995) Visual integration in the split brain. Neuropsychologia 33, 937-959.
Crick, F. (1994) The astonishing hypothesis. Simon and Schuster
Fingelkurts AA and Fingelkurts AA (2002) Operational architectonics of the human brain biopotential field: towards solving the mind-brain problem. Brain and Mind 2, 261-296.
John E.R. (2002) The neurophysics of consciousness. Brain Research Reviews 39, 1-28.
Köhler W (1940) Dynamics in psychology. Liveright, New York, 158pp
Lashley K (1950) In search of the engram. Symposium of the Society for Experimental Biology 4, 454-482.
Lashley KS, Chow KL and Semmes J (1951) An examination of the electric field theory of cerebral integration. Psychological Review 58, 123-136.
Libet B (1994) A testable field theory of mind-brain interaction. Journal of Consciousness Studies 1(1) 119-126.
McFadden J (2000) Quantum evolution: the new science of life. Norton NY, London, 338 pp.
McFadden J (2002a) Synchronous firing and its influence on the brain’s electromagnetic field: evidence for an electromagnetic field theory of consciousness. Journal of Consciousness Studies 9 (4) 23-50.
McFadden J (2002b) The conscious electromagnetic information (cemi) field theory: the hard problem made easy? Journal of Consciousness Studies 9(8) 45-60.
McFadden J (2006) The CEMI field theory: seven clues to the nature of consciousness. In The Emerging Physics of Consciousness ed. Jack A. Tuszynski. Springer Berlin Heidelberg 2006. pp 385-404.
McFadden J (2013) The CEMI field theory: closing the loop. Journal of Consciousness Studies 20 (1-2) 153-168.
Pockett S (1999) Anesthesia and the electrophysiology of auditory consciousness. Consciousness and Cognition 8, 45-61.
Pockett S (2000) The nature of consciousness: a hypothesis. iUniverse.com, Lincoln Nebraska. 190pp.
Pockett S (2002) Difficulties with the electromagnetic field theory of consciousness. Journal of Consciousness Studies 9 (4) 51-56.
Pockett S (2004) Does consciousness cause behavior? Journal of Consciousness Studies 11 (2) 23-40.
Pockett S (2011) Initiation of intentional actions and the electromagnetic field theory of consciousness. Humana.Mente 15 159-175.
Pockett S (2012) The electromagnetic field theory of consciousness: a testable hypothesis about the characteristics of conscious as opposed to non-conscious fields. Journal of Consciousness Studies 19 (11-12) 191-223.
Pockett S, Banks WP and Gallagher S (2006) Does consciousness cause behavior? MIT Press, Cambridge Mass. 364 pp.
Pockett S, Zhou ZZ, Brennan BJ and Bold GEJ (2007) Spatial resolution and the neural correlates of sensory experience. Brain Topography 20 1-6.
Rose D (2006) Consciousness: philosophical, psychological and neural theories. Oxford University Press, Oxford, New York, 452 pp.
Sperry RW, Miner N and Myers RE (1955) Visual pattern perception following subpial slicing and tantalum wire implantations in the visual cortex. Journal of Comparative and Physiological Psychology 48, 50-58
Wegner DM (2002) The Illusion of Conscious Will (Cambridge MA: MIT Press).