The neural binding hypothesis proposed decades ago (Crick & Kock, 1990) is that if some nerves represent a trunk and others its leaves, they represent a tree when they fire in synchrony, so synchrony combines information, but why isn’t clear as synchronizing physical oscillators doesn’t unify their information. Yet neural synchronies seem to unify cognitive outputs as they:
a. Accompany face recognition. Face recognition occurs when distant nerves synchronize with no phase lag (Rodriguez et al., 1999).
b. Accompany object recognition. In the visual cortex, the “… selection of responses for further processing is associated with enhanced synchronization rather than increased firing.” (Singer, 1999), p62, so synchrony could let one object direct responses.
c. Represent odors. Different smells produced odor-specific synchronies in locust olfactory nerves for different smells but not for the same smell (Laurent et al., 1996), so the observation of odors could depend on nerve synchrony.
d. Are transient. Neural synchronies are often brief and hard to detect (Singer et al., 1997), just as sensory experiences are often fleeting moments.
e. Accompany cognitions. Beta/gamma brain waves correlate with cognitive functions like attention, recall, sense integration, and motor coordination (Uhlhaas, 2009), p8, so synchrony could provide the binding of neural functions they require.
Studies from insects, cats, monkeys, and humans support the theory that neural groups synchronize to combine their results (Fries, 2015), p220, giving a mood of optimism that the unity of consciousness is entering the realm of science:
“Beliefs about the basis of subjective experience have slowly evolved, from mystical notions of the soul and a disembodied mind to acceptance of the proposal that consciousness must derive from neurobiological processes.” (John, 2005), p143.
Yet if consciousness derives from neurobiological processes, it isn’t unique to us. Locust nerves synchronize, so if synchronies create our conscious experience, insects must be conscious to a degree, albeit on a diminished scale. Consciousness as the ability to unify brain observations then began in other animals, who dimly observe what we brightly do. Our brain also has many synchronies not one, so regions that bind locally but not globally provide a basis for subconscious effects. If the degree of consciousness depends on the number of nerves synchronizing, people under anesthetic, sleeping, or sleepwalking have less consciousness not none at all.
Further evidence that neural synchronies create consciousness is that after a stimulus, they build-up in a time-frame that reflects our experience of it (John, 2005):
1. 50 milliseconds: P1 waves occur as nerve synchronies in primary sensory cortex areas that register input features.
2. 130 milliseconds: N1 wave synchronies link the cortex to the thalamus/limbic system.
3. 210 milliseconds: P2 waves link higher cortex layers to the thalamus/limbic system.
4. 300 milliseconds: Sustained P300 gamma oscillations synchronize the frontal and parietal lobes with zero-delay in what is considered to be a human perception.
Sense input seems to trigger local synchronies in sensory areas, then long-range synchronies add emotions, memory, and language giving a global conscious experience in under half a second. These stages are supported by the structure of the human cortex, a nested hierarchy that processes data in six layers labelled I to VI. The first unification after the nerve is a hundred or so nerves about the thickness of a hair called a microcolumn:
“… current data on the microcolumn indicate that the neurons within the microcolumn receive common inputs, have common outputs, are interconnected, and may well constitute a fundamental computational unit of the cerebral cortex …” (Cruz, 2005).
About a hundred microcolumns then form a cortico-cortical column that sends axons to nerves nearby. They in turn combine into a macrocolumn of about a million neurons about 3mm wide with more cortical links. Macrocolumns then combine into the 32 Brodmann areas (Figure 6.37), each with about a hundred million neurons, that specialize in different functions like language.
The cortical architecture is then (Nunez, 2016), p91:
1. Microcolumns. About a hundred neurons (∼.03mm).
2. Cortico-cortical columns. About a thousand neurons (∼.3mm).
3. Macrocolumns. About a million neurons (∼3mm).
4. Brodmann areas. About a hundred million neurons (various sizes)
Brodmann areas then combine into five lobes separated by deep fissures (Figure 6.38). The occipital lobe handles visual data, the parietal lobe handles skin data like touch, pain, and temperature, the temporal lobe handles sound and memory data, and the frontal lobe handles plans and intentions, so a person with frontal lobe damage may know how to behave but can’t stop inappropriate acts like touching. These lobes together are one hemisphere, and two connected hemispheres are the cortex.
The cortex divides the work of processing input among various regions, each specializing in its own data to produce results in parallel, and at the same time creates neural synchronies that bind them. Specialization and integration can then evolve together, as synchronizing a neural hierarchy doesn’t affect its information result. The only question then is how neural synchronies build up to produce the unified conscious experience that we report?