Scientific Understanding of Consciousness
Consciousness as an Emergent Property of Thalamocortical Activity

Scientists’ Hypotheses/Conjectures/Theories

These hypotheses/conjectures/theories are based upon scientific principles and are thoughtfully based upon an understanding of the current state of knowledge by mature scientists. Whether the proposals are accepted will depend on future experimental observations. Some of the proposals seem intuitively reasonable; others seem very far-out, rather remote possibilities.

Complexity/Self-Organization/Emergence

A number of scientists have suggested or endorsed ideas related to Complexity/Self-Organization/Emergence.

Physicists refer to as the "edge of chaos" in dynamical systems: the emergence of "complexity" at the boundary between stability and chaos. (Ramachandran; Illusions of Body Image, 55)

Order for free - self-organization that arises naturally. (Kauffman, 71)

All complex systems with chaotic properties can self-organize. Self-organization is more likely to be achieved in undirected states, such as meditation, fantasy, or reverie, that border on waking. Dreaming may be our most creative conscious state, one in which the chaotic, spontaneous recombination of cognitive elements produces novel configurations of information -- new ideas. (Hobson; Consciousness, 45)

Dreamlike state modulated by the senses

Nervous system is primarily self activating and capable of generating a cognitive representation of the external environment even in the absence of sensory input, as for example in dreams. (Llinás & Paré; Brain Modulated by Senses, 4)

Dreaming and wakefulness are so similar from electrophysiological and neurological points of view that wakefulness may be described as a dreamlike state modulated by sensory input. (Llinás & Paré; Brain Modulated by Senses, 6)

Convergence Zones

Access to concrete knowledge of higher hierarchical status requires structures in anteriorly placed temporal cortices, whereas access to concrete knowledge of lower complexity only requires posterior occipital cortices. (Domasio; Convergence Zone, 68)

The highest-level processing of the visual system, combining simpler features of perceptual objects, occurs in the inferotemporal area with its enormous convergence of inputs about visual features. At this stage of visual processing, no topography is identified. (Eichenbaum; Olfactory Perception and Memory, 177)

Vision, audition, and somatosensation merge in temporal and parietal association areas of the neocortex well before the common paths into the entorhinal cortex, amygdala, and prefrontal convergence sites. (Eichenbaum; Olfactory Perception and Memory, 192)

Pattern Theory with Gestalts

Pattern theory says that tightly coupled cortical areas seek, via some kind of relaxation functionality, to arrive at a mutual agreement in which lower areas specific data form a fit with known, more abstract categorizations stored in higher areas' memory of prior activity. (Mumford; Neuronal Architectures, 135)

Correlations among nearby neurons

If, during a time interval, the signals on a set of neurons are significantly correlated, the set is interpreted as being bound during that interval. (von der Malsburg; Binding Problem, 137)

Correlations involving just two neurons cannot play a central role because binary correlations are too easily drowned in the noise of accidental coincidences. Therefore, the significant correlations will be those involving larger numbers of neurons, perhaps near-simultaneous spikes on fifty neurons, which can easily be recognized as being statistically significant. (von der Malsburg; Binding Problem, 137)

Temporal bandwidth of neural signals is severely limited. It is not possible within short periods of time to express complicated multilevel binding structures in terms of signal correlations. (von der Malsburg; Binding Problem, 140)

Stochastic Nature of Neuronal Behavior

Because single neurons have small and uncertain effects on other neurons, the cortical description must be carried out in terms of neuronal populations rather than at the level of individual cells. (Stevens; Cortical Theory, 242)

A given axon generally arborizes over a considerable region of cortex with an arbor diameter of perhaps 0.5 mm, and forms about 2000 boutons, each of which makes one or two synapses. (Stevens; Cortical Theory, 242)

The overall stochastic nature of neuronal behavior suggests that the physiologically meaningful signal from cortex should be the average firing rates of a population of perhaps 100 to 1000 neurons near a particular cortical site. (Stevens; Cortical Theory, 243)

The behavior of cortex at a particular point would then be described by the firing in a population of neurons. The total firing that represents this population would be determined by a weighted average of the appropriate neurons in the cortical region that surrounded the point, perhaps with weights that are described by a spatial Gaussian. Moving from one cortical location to an adjacent one, the variables describing cortical state would vary continuously with cortical position. (Stevens; Cortical Theory, 243)

Cortical neural signals have a very pronounced stochastic structure, and nervous tissue is evidently designed to create and preserve it. An assumption of statistical independence of signals therefore must be faulty, and strong signal correlations must be present in the brain. (von der Malsburg; Binding Problem, 139)

Correlations involving just two neurons cannot play a central role because binary correlations are too easily drowned in the noise of accidental coincidences. Therefore, the significant correlations will be those involving larger numbers of neurons, perhaps near-simultaneous spikes on fifty neurons, which can easily be recognized as being statistically significant. (von der Malsburg; Binding Problem, 137)

Crick hypothesis

 

Llinás hypothesis for fast electrical connectivity in the cortex.

 

Penrose/Hameroff hypothesis for quantum microtubles

Some people believe that qualia represent very profound events in neuronal function dealing with quantum mechanical structures of neurons that include the detailed organization of microtubules and microfilaments. Llinás doubts that this topic is worth pursuing at any serious level. (Llinás; I of the Vortex, 209)