Piero Scaruffi(Copyright © 2013 Piero Scaruffi | Legal restrictions )
These are excerpts and elaborations from my book "The Nature of Consciousness"
Time-based binding does not look for the "place" but for the "time" at which the binding of our conscious experience occurs.
The German neurologist Christof Koch (“Collective Oscillations in the Visual Cortex“, 1989) discovered that at, any given moment, a very large number of neurons oscillates in synchrony, reflecting something that was captured by the senses, but only one pattern is amplified into a dominant 40 Hz oscillation. That is the "thing" the individual is conscious of. Out of so many oscillations of synchronized cells in the brain, one is special and happens to have a frequency of 40 Hz.
The British biologist Francis Crick originated the view that synchronized firing in the range of 40 Hertz in the areas connecting the thalamus and the cortex might explain consciousness; that consciousness arises from the continuous dialogue between thalamus and cortex. Awareness of something requires "attention" (being aware of one object rather than another), and attention requires "binding" (banding together all neurons that represent aspects of the object). Crick believes that binding occurs through a synchronous (or "correlated") firing of different regions of the brain. During attention, all the neurons that represent features of an object fire together. It is not just the frequency of firing of the neurons that matters, but the moments when they fire. The main difference between Llinas and Crick is in their background. Crick studied visual awareness and so is interested in consciousness that arises from external stimuli. Llinas, on the contrary, is more interested in consciousness that does not arise from external stimuli (what we call "thought").
Koch and Crick focused on the "neuronal correlates of consciousness" (NCC): the "thing" in the brain that corresponds to states of awareness. One of the first clues (although apparently disconcerting) is that much of the neural activity of the brain is not conscious at all: we are not aware of most of what our brain does. Most of the time (e.g., habits, instinct, etc.) the brain makes key decisions without "us" being conscious of those decisions.
Because most neuronal activity does not yield a state of awareness, they were led to believe that multiple forms of neuronal activity exist (this is almost a tautology). They speculated that one could potentially be conscious of many competing views, but only one "wins" the competition and results in awareness of the corresponding view.
All body cells are, to some extent, influenced by what happens to the body, but only a minority of the body cells represent external stimuli in an "explicit" manner: Koch and Crick believe that one is only conscious of features that are encoded "explicitly" by some neuronal assembly. The other way to find them is to listen to the way they oscillate. The electric potential of the brain as a whole exhibits oscillatory behavior in different frequency bands: the dominant rhythm for resting individuals is in the "alpha" band (8-12 Hz); the rhythm for normal cognitive activity is in the "beta" band (15-25 Hz) or, for more complex operations, in the "gamma" band (30 Hz or higher); sleep is in the "delta" band (1-4 Hz). Each of these "oscillations" is caused by some synchronous behavior ("firing") of many neurons.
The "binding" problem is the problem of how the various features are integrated in the brain into the perception of the object as a whole, especially when the same brain is integrating other features of other objects. The German physicist Christoph von der Malsburg (“How are Nervous Structures Organized?”, 1983) was the first to propose that synchronization could be the solution to the "binding" problem: the neurons working on one object are synchronized, and they are not synchronized with other populations of neurons that are working on other objects. There is one oscillatory behavior by neurons that seems to be associated with awareness, and it is in the 30-70 Hz range, with a peak around 40 Hz. Koch and Crick (“Towards a neurobiological theory of consciousness“, 1990) claimed that this oscillation accounts for consciousness (i.e., that the set of those synchronized neurons "is" the NCC for the current state of awareness).
Koch and Crick believe that several such "coalitions" of neurons exist at every point in time, and a sort of Darwinian selection determines which one (and only one) wins and results into awareness.
Another clue to finding the NCC is the cholinergic system: consciousness only occurs when there is an adequate supply of acetylcholine neurotransmitters, which are regulated by the brainstem (people whose brainstem is damaged lose consciousness).
The brain has a convoluted structure, and the way it represents an experience is even more convoluted, but we perceive an experience as a sequence of events. Koch thinks this has to do with the fact that, at every point in time, only one coalition is the winning one. It may change all the time, but we perceive an ordered sequence of events, because every other coalition that is active at the time is suppressed. We do not perceive the convoluted activity of the brain, which is analyzing an overwhelming amount of data, but only those events that correspond to the winning coalition.
Koch divides short and long-term memory based on the underlying mechanism: long-term memory is caused by a physical rewiring of the brain (strengthening of connections), whereas short-term memory is caused by a sustained firing pattern by an assembly of neurons. Koch proves that consciousness depends on the latter, not on the former. Short-term (or, better, working) memory could provide a sort of "Turing test for consciousness": any being that displays a working memory is likely to be conscious.
Koch also speculated on why we are conscious at all. After all, we do not need consciousness: the brain makes most of the key decisions in an unconscious way. The autonomic system directs the organs to do their job, and "instinct" helps the body survive. Qualia (the qualitative aspects of things) are "symbols" that help the brain synthesize, summarize, huge amounts of data. Seeing red or feeling pain are shortcuts to handling huge amounts of sensory data. Qualia are symbols that summarize the state of the world (including the body itself). This is the "executive summary hypothesis".
Koch believes in a non-conscious homunculus, residing in the front of the forebrain, that handles the information stored in the back of the cortex (the sensory regions) and that does all of the "thinking". The front of the cortex is looking at the back. This homunculus is beyond consciousness, the same way that automatic, zombie-like behavior is beyond consciousness, although one is "above" it (supramental) and the other is "below" it (submental). Consciousness is an intermediate level, which is conscious not of the homunculus and its work (its "thoughts") but only of representations of the homunculus' work in the form of inner speech.
Consciousness resides at an intermediate level, which is conscious not of the homunculus and its work (its "thoughts") but only of representations of the homunculus' work in the form of inner speech. We are not conscious of the homunculus that is making decisions for us, and we are not conscious of the real world. We are only conscious of the reality that we manufacture.
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