Imagine standing outside on a sunny day in the middle of a green, sprawling park, as a little boy bounces up to you and hands you a red flower. You take it and thank him with a smile. As you hold up the flower to admire its beauty, different parts of the sunlight are either absorbed or reflected by the petals, resulting in a 600 nanometers wavelength of light bouncing off the petals, passing through the front of your eye, and hitting your retinal cells, causing electrical signals to be transmitted through your optic nerve to various visual processing areas in your brain. Somewhere along the way, as all those neurotransmitters swim about in the synapses, as all those ion channels open and close, as all those action potentials flash across their respective axons – somehow, almost as if by magic, all that neural activity results in you seeing the redness of the red flower before you. This is the great mystery of consciousness: How do all those little bits of electricity, flashing around in our brains, give rise to the subjective, phenomenological experience of human perception, emotion, thoughts, conscious control of our actions, the irrevocable feeling that we, as free individuals, have a physical and mental existence in the context of a larger physical world?
No wonder philosophers back in the olden days felt compelled to invoke dualism, the idea that mind and body are two separate entities, and even made up of completely different substances – the famous “soul” theory. The problem with this view, of course, is how would a non-physical “soul” influence and control a physical body? Philosophers since Descartes have come up with increasingly convoluted metaphysical theories to deal with the so-called “‘explanatory gap’ between the physical and the phenomenal facts… the fact that when someone’s perceptual system is in a certain physical condition, that person has an experience with a certain phenomenal character” (Shoemaker, 2007). Despite all the philosophical work that has been done on consciousness, and the advances of brain-imaging techniques such as fMRI and PET scans, consciousness is still a relatively poorly-understood topic in scientific terms. In fact, the problem with consciousness is precisely the fact that the subjective quality of it seems unexplainable in scientific terms. Ramachandran (1998) illustrates this problem with a thought experiment in Phantoms in the Brain:
Imagine that you are a a color-blind scientist, who can only see the world in black and white. Your condition makes you supremely interested in color perception, and so you study how the human perceptual system works when faced with colorful stimuli. After spending a lot of time studying rods and cones and the eye and the visual pathway, you learn everything there is to know about color vision, to the point that you can monitor a person’s neural activity and predict what color he or she is seeing in advance. However, being color-blind, you still have no idea what colors look like – the redness of red or the blueness of blue, for example – even though you know everything else about how people perceive colors. Ramanchandran uses this thought experiment as a lead in to his definition of “qualia”, that is, “aspects of my brain state that make the scientific description incomplete – from my point of view” (p. 230).
Qualia (singular “quale”) is a philosophical term that is often used to describe the subjective, raw sensations that individuals feel, such as the greenness of a leaf, the high-pitched quality of a tone of a certain frequency, the luscious, sweet, melting feel of chocolate on your tongue, and so on. These sensations are often described as ineffable. Can you describe the redness of red? Or the sweetness of sweetness? You can certainly describe the effects of “red” and “sweetness” on you, and the underlying neurological, biological, chemical, and physical qualities of it, such as the structure of taste buds that respond to “sweetness”, but it is impossible to directly describe the actual quality itself. Ramachandran (1998) provides yet another thought experiment illustrating the seeming ineffable quality of qualia. He asks readers to imagine an intelligent species of Amazonian electric fish, who have “the ability to sense electrical fields using special organs in its skin” (pp. 230-231). You can study their biological structures as much as you want, and come up with a complete scientific explanation of the electricity-sensing process, but you will never be able to know what it actually feels like to sense electricity, any more than the color-blind scientist in the previous example will ever know what lights of certain wavelengths actually “look” like after being processed by a human perceptual system.
However, Ramachandran (1998) argues that the so-called “gap between brain and mind” does not exist (p. 231). He argues that qualia seem to be completely private and ineffable simply because of a translation barrier. Spoken language is inadequate to convey the “language of nerve impulses – the spatial and temporal patterns of neuronal activity that allow us to see red, for example” (p. 231). He then proceeds to suggest that if we bypassed this language barrier, for example, by hooking up a normal human’s neurons to the color-blind scientist’s, he too would be able to experience color qualia. Edelman & Tononi (2000) seem to concur, and they expand a similar argument to the issue of consciousness as a whole (qualia being merely the subjective, raw sensation part of consciousness – although Prinz (2007) would argue that all consciousness is perceptual, and hence all aspects of consciousness involves qualia, including willful actions or movement which involve proprioception, and even abstract thoughts, which usually have weak auditory or visual qualia – the “voice in the head” which usually happens when people think – and whose deeper-structure meanings are associated with emotional and sensory qualia).
Edelman & Tononi state that scientific descriptions cannot convey qualia because “we cannot give rise to [qualia] without first giving rise to appropriate brain structures and their dynamics within the body of an individual organism” (p. 15), which is similar to Ramachandran’s argument that spoken language cannot convey the “language” of brain structures which give rise to qualia without those brain structures themselves. Edelman & Tononi take this argument a step further and argue that not only can we not expect science to provide an adequate description of subjective conscious states, we should not do so because “no scientific description or explanation can substitute for the real thing” (p. 15). Edelman & Tononi use the example of a hurricane: we can explain how it forms, under what conditions it will form, and its various physical properties. But no one expects an explanation of a hurricane to be one, or to cause one to happen. So why should we expect scientific descriptions of qualia to recreate qualia? Therefore, in this limited sense, consciousness is no more special than other psychological or physiological phenomena, and should be treated as such. From this, Edelman & Tononi argue that far from being off-limits to science, consciousness, qualia, and the apparent “explanatory gap” can be studied and explained scientifically, in the same way a hurricane can be studied.
In their book, A Universe of Consciousness, Edelman & Tononi (2000) investigate various universal aspects of consciousness, and eventually come up with a theory of the neurological basis for consciousness, called the “dynamic core hypothesis”. This hypothesis stems from their observation that “a significant amount of neural activity goes on without directly contributing to conscious experience” (p. 142). Many of our bodily functions, such as respiration, digestion and blinking, are for the most part automated, as are some of the actions that we are so practiced in that we can perform them without conscious thought, such as maintaining balance while walking and producing speech. The effectiveness of subliminal activation studies in producing some sort of physical or physiological change in the subjects without them actually being consciously aware of the stimuli presented suggest that neurons that are activated for an extremely short period of time do not contribute to conscious experience.
It follows, then, that a conscious state is caused by specific groups of neurons at any given time, instead of the entire brain. More specifically, according to the dynamic core hypothesis, such a group of neurons can contribute to conscious experience “only if it is part of a distributed functional cluster that, through reentrant interactions in the thalamocortical system, achieves high integration in hundreds of milliseconds”, and that in order for conscious experience to be sustained, “it is essential that this functional cluster be highly differentiated” (p. 144). The second part of the hypothesis is supported by the fact that EEGs of slow wave sleep and epilepsy patients show that the firing of neurons become highly synchronized, as opposed to “waking, when groups of neurons dynamically assemble and reassemble into continuously changing patterns of firing” (p. 72). Moreover, according to Edelman & Tononi, participants looking into a “featureless field of vision (a Ganzfield), all color would soon drain from the field of vision, after which visual experience itself would fade” (p. 74). In other words, differentiation of neuronal activity seems to contribute to consciousness, while homogenous brain activity is associated with loss of consciousness.
According to Edelman & Tononi (2000), the term “dynamic” refers to the fact that the dynamic core is constantly in a state of differentiation and fluctuation. It is not localized in any part of the brain, but will move depending on where the individual’s attention is directed. For example, if the individual looks up from reading a book to focus on the sound of a piano playing, the dynamic core that might have originally been concentrated and fluctuating around Wernicke’s area might “move” nearer to the auditory cortex (in terms of neurons in one area showing a general pattern of deactivation and neurons elsewhere starting to fire more rapidly or with a more differentiated pattern). In this way, the dynamic core will not stay permanently localized in any part of the cortex, and accounts for the fact that our conscious state is constantly, rapidly changing as our attention shifts. In short, the dynamic nature of the dynamic core is crucial to the “serial nature of conscious experience – the fact that one conscious state of thought is followed by another”, as the core shifts without losing its coherence (p. 151).
This brings us to the term “core”, which refers to the integrated nature of the dynamic core, whose neuronal groups are constantly “strongly interacting among themselves and… have distinct functional borders with the rest of the brain at the time scale of fractions of a second” (p. 144). The dynamic core is, therefore, a united, interacting whole. This property of the dynamic core both explains and is supported by the integrated nature of consciousness and qualia. Take, for example, any ambiguous picture, such as the rabbit-duck ambiguous figure. A human will only be able to see either the rabbit or the duck at any given time, suggesting that consciousness only has room for one of the mutually exclusive subjective experiences in order to preserve the unity and integrity of the subjective state. The dynamic core, because of its high level of integration, has only room for one global state (in this case, resulting in either a rabbit or duck quale) to the exclusion of all other global states. Of course, since the global state of the dynamic core is constantly changing, it is possible that the perception of ambiguous figures may flip from time to time, such as how a Necker’s cube can seem to change direction. The integrated nature of the dynamic core also accounts for the limited capacity of consciousness. If too many partially independent subgroups of neurons fire at the same time, the unity and coherence of the functional cluster may be compromised, which may result in some of the subgroups breaking off from the border of the dynamic core and sinking away from conscious awareness.
So far, the dynamic core seems to be a very plausible neurological mechanism for consciousness in general. Edelman & Tononi (2000) even proposed a specific way in which the dynamic core can give rise to qualia. Since the dynamic core is made up of all these tightly interrelated, highly integrated subgroups of neurons that are constantly feeding back into each other, a small change in a small subgroup of neurons due to a particular stimulus can cause a cascade of change through the entire dynamic core, which holistically creates the experience of a quale, since “each quale corresponds to a different state of the dynamic core” (p. 157).
Lastly, Edelman & Tononi (2000) suggest that the dynamic core, even though it is constantly moving about, is active mostly in the thalamocortical section of the brain, since the most evidence of conscious activity seems to originate from there. In his paper, “Three Laws of Qualia”, Ramachandran (1997) narrows down the localization of consciousness to the temporal cortex. (In terms of the dynamic core hypothesis, this suggests that a lot of the time the dynamic core will tend to have its focus on the temporal cortex.) Ramachandran points to various cases of temporal lobe epilepsy patients to support his assertion. Such patients experience extremely vivid hallucinations that “look and feel like the real thing” (p. 451), which suggest that the temporal lobe is responsible for the subjective sensations of qualia. Others see cosmic significance even in common, everyday objects, suggesting that the temporal lobe is responsible for the “attachment of emotional significance and value labels to objects and events” (p. 451), also part of consciousness. Some patients experience “out of body” sensations, implying that the temporal lobe is also involved in body image, which is crucial to our conscious sense of self. Some patients become extremely religious, and convinced that they are privy to some cosmic truth, which suggests that the temporal lobe is involved in attaching the emotional qualia of conviction and truth to thoughts or beliefs. Others undergo “doubling of consciousness” (p. 451), suggesting that the temporal lobe is involved in the unity of self and the dynamic core. Yet others experience loss of free will, such as in akinetic mutism, which suggests that parts of the temporal lobe are crucial to create a sense that the self is in control and able to make choices.
Not only does he provides links between structures in the brain and consciousness, Ramachandran (1997) also draws up three “laws of qualia” in the same paper that are not incompatible with the dynamic core hypothesis. The first law posits that a stimulus has to be irrevocable for it to possess qualia. The difference between the “filling in” of the blind spot in front of you, and the blind spot behind your head, for example, is that you will see the “filling in” of the blind spot no matter how hard you try to imagine otherwise, while you have leeway to imagine that anything could be going on behind your head. The second law states that the result of your perception of the stimulus should be flexible. For example, if someone shines a light into your eye while you are unconscious, your pupils will contract. There is no choice involved. In contrast, if you see an attractive person walking down the road, you may choose to do any number of things – ogle them, wave at them, and so on. Your pupils may still dilate in this case (which usually happens when you see something attractive), but you will not be conscious of your pupils dilating (since that constitutes an inflexible output), while you will be of the attractive individual. Experiencing qualia means you have the freedom to interpret or react to the qualia in flexible ways. The third law states that for a stimulus to have qualia, it has to pass into short-term memory. This law seems to be nothing more than common sense since if a stimulus is not around for long enough to get into your short-term memory, such as in subliminal activation studies, you will not be able to perceive it consciously. Dynamic core theory explains this effect in terms of the neuronal subgroup not firing long enough to have sustained interaction with the dynamic core, and hence the stimulus does not pass into consciousness.
The dynamic core hypothesis and Ramachandran’s three laws of qualia, together with other similar scientific theories of consciousness, allow for functional, scientific investigation of consciousness, which is a fortunate thing, as thought experiments and philosophical arguments ultimately have to be backed up by empirical evidence. As of the moment, the philosophical literature on consciousness far outweigh the scientific literature, but there seems to be a trend of both philosophers and scientists moving towards a blend of the two, which will hopefully result in greater strides in our understanding of that greatest of scientific mysteries, consciousness and qualia.
References
Edelman, G.M. & Tononi G. (2000). A Universe of Consciousness. New York: Basic Books.
Prinz, J. (2007) All Consciousness is Perceptual. In B. P. McLaughlin & J. Cohen (Eds.), Contemporary Debates in Philosophy of Mind (pp. 335-357). Oxford: Blackwell Publishing.
Ramachandran, V.S. & Hirstein, W. (1997). Three Laws of Qualia. Journal of Consciousness Studies, 4(5-6), 429–458.
Ramachandran, V.S. (1998) Phantoms in the Brain: Probing the Mysteries of the Human Mind. New York: Harper.
Shoemaker, S. (2007) A Case for Qualia. In In B. P. McLaughlin & J. Cohen (Eds.), Contemporary Debates in Philosophy of Mind (pp. 319-332). Oxford: Blackwell Publishing.
