During the course of responding to my previous post, I came upon a paper by Johnjoe McFadden Synchronous Firing and Its Influence on the Brain’s Electromagnetic Field Evidence for an Electromagnetic Field Theory of Consciousness.
This is a remarkable paper written in 2002 that outlines his theory (cemi) and makes some of the strongest arguments for EM field theories of consciousness I’ve seen. I don’t know how much has changed since it was written. There is an enormous amount of detail in it. So caution is called for. Some of the studies he cites may have been invalidated and others may exist that support or disapprove some of his arguments. I am breaking this post into two parts as I absorb the paper. This one is focuses on eight specific testable predictions he makes for his theory:
(1) Stimuli that reach conscious awareness will be associated with em field
modulations that are strong enough to directly influence the firing of motor
neurons.
(2) Stimuli that do not reach conscious awareness will not be associated with em field modulations that affect motor neuron firing.
(3) The cemi field theory claims that consciousness represents a stream of information passing through the brain’s em field. Increased complexity of conscious thinking should therefore correlate with increased complexity of the brain’s em field.
(4) Agents that disrupt the interaction between the brain’s em field and neurons will induce unconsciousness.
(5) Arousal and alertness will correlate with conditions in which em field fluctuations are most likely to influence neuron firing; conversely, low arousal and unconsciousness will correlate with conditions when em fields are least likely to influence neuron firing.
(6) The brain’s em field should be relatively insulated to perturbation from exogenous em fields encountered in normal environments.
(7) The evolution of consciousness in animals should correlate with an increasing level of electrical coupling between the brain’s endogenous em field and (receiver) neuron firing.
(8) Consciousness should demonstrate field-level dynamics.
McFadden goes on to discuss the existing evidence for each prediction. Various selected content from the ones that caught my attention follows. His discussion of number 8 is the most interesting even though there is less experimental evidence for it at the time of the paper. All content below is quoted directly from paper. Highlights in bold are mine.
Prediction 1
Sensory or motor information that is transmitted just by neuron firing will tend to scale arithmetically: the greater the stimulus or response, the more neurons are likely to be involved. However, because the em field is a wave-mechanical phenomenon the magnitude of its modulations will be proportional only to the number of those neurons that fire synchronously. The cemi field theory therefore predicts that conscious awareness will not correlate with neuron firing per se but with the synchrony of neuron firing. As outlined in the Introduction, numerous studies have indeed indicated that whereas neuron-firing patterns alone do not correlate with awareness, their level of synchrony does.
Prediction 2
There is abundant evidence that the loss of awareness of repeated stimuli during habituation is associated with a reduction in amplitude of either EEG or MEG evoked potential signals (Coull, 1998; Hirano et al., 1996) and thereby the synchronous neuron firing patterns that generate those signals. Loss of awareness therefore correlates with reduced disturbance to the brain’s em field (Anninos et al., 1987; Hulstijn, 1978; Leaton and Jordan, 1978; Rockstroh et al., 1987).
Prediction 4
Examining the third prediction, there is evidence that anaesthetics that decrease awareness of stimuli disrupt synchronous firing (Southan and Wann, 1989; Whittington et al., 1998) and thereby reduce the influence of the em field on neuron firing. The onset of unconsciousness due to a variety of agents e.g. asphyxia or anesthesia is associated with a reduction of amplitude of EEG signals (McPherson, 1998), indicating that loss of consciousness is associated with disruption to neuronal synchronization (Speckmann and Elger, 1998) and consequent weak endogenous em fields. As mentioned above, disruption of synchronous firing in insects by treatment with picrotoxin reduces their ability to discriminate between scents.
Prediction 5
The cemi field theory predicts that the increased levels of arousal (increasing conscious control of actions) should be associated with strong coupling between the brain’s em field and neuron . Increased amplitude of visually evoked potentials is also associated with short reactions times in monkeys (Chalupa et al., 1976; De Giorgio et al., 1993). The level of spatial coherence of EEG patterns — which is a reflection of the coherence of the underlying endogenous em fields — is also found to correlate with attention and awareness. For instance, in a recent study, the level of EEG spatial coherence was found to be related to the level of creativity needed to solve a problem (Jausovec and Jausovec, 2000). Spatial coherence was also found to increase during transcendental meditation (Travis and Wallace, 1999). Conversely, loss of EEG spatial coherence was found to correlate with increasing cognitive impairment in HIV patients (Fletcher et al., 1997).
Prediction 6
The high conductivity of the cerebral fluid and fluid within the brain ventricles creates an effective ‘Faraday cage’ that insulates the brain from most natural exogenous electric fields. A constant external electric field will thereby induce almost no field at all in the brain (Adair, 1991). Alternating currents from technological devices (power lines, mobile phones, etc.) will generate an alternating induced field, but its magnitude will be very weak. For example, a 60 Hz electrical field of 1000 V/m (typical of a powerline) will generate a tissue field of only 40 µV/m inside the head (Adair, 1991), clearly much weaker than either the endogenous em field or the field caused by thermal noise in cell membranes. Magnetic fields do penetrate tissue much more readily than electric fields but most naturally encountered magnetic fields, and also those experienced during nuclear magnetic resonance (NMR) scanning, are static (changing only the direction of moving charges) and are thereby unlikely to have physiological effects. Changing magnetic fields will penetrate the skull and induce electric currents in the brain. However, there is abundant evidence (from, e.g., TMS studies as outlined above) that these do modify brain activity. Indeed, repetitive TMS is subject to strict safety guidelines to prevent inducing seizures in normal subjects (Hallett, 2000) through field effects.
Prediction 8
The last prediction of the cemi theory — that consciousness should demonstrate field-level dynamics — is perhaps the most interesting, but also the most difficult to approach experimentally. In principle it should be possible to distinguish a wave-mechanical (em field) model of consciousness from a digital (neuronal) model. Although neurons and the fields generated by neurons hold the same information, the form of that information is not equivalent. For instance, although a complete description of neuron firing patterns would completely specify the associated field, the reverse is not true: a particular configuration of the brain’s em field could not be used to ‘reverse engineer’ the neuron firing patterns that generated that field. This is because any complex wave may be ‘decomposed’ into a superposition of many different component waves: a particular field configuration (state of consciousness) may be the product of many distinct neuron-firing patterns. The cemi field theory thereby predicts that if distinct neuron firing patterns generate the same net field then, at the level of conscious experience, those firing patterns should be indistinguishable. In principle at least, this issue could be resolved experimentally.
Experiments could be designed to investigate whether wave-mechanical interference is a factor in conscious awareness. Field level informational processing may also endow consciousness with properties that are absent, or more complicated to emulate, in a digital system. For instance, wave-mechanical dynamics may allow Fourier-type (harmonic analysis) of information held in the conscious field, providing a possible mechanism for the ability of some individuals to hear pure tones in complex sound waves. MacLennan (1999) has recently argued that many mind processes may usefully be described as field-level computations.
