These are the talking points for the paper I presented at the Science of Consciousness conference in Stockholm, May 3, 2011

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Our bodies inhabit a classical 3-dimensional world. Our atoms inhabit a quantum mechanical world.  What insights about consciousness and conscious experience come from a consideration of the quantum and classical brain? 

We’ll consider quantum effects at microtubules, within the synapse and in gap junctions. Then we’ll discuss how these effects may influence subjectivity, qualia and meditation experiences

Hameroff and Penrose have examined quantum processes within microtubules of a cell. Microtubules form the cytoskeleton of eukarotic cells, including brain cells, and provide structure, transport organelles, and participate in cell division. 

These authors elegantly detail how conformational states of tubulin that comprise microtubules are sensitive to internal quantum events and so exist in quantum superimposition of different states. 

According to Penrose, quantum superimposition is displacement of mass from itself.  He and Hameroff predict that the coupling between mass and deformations of space-time cause an objective collapse of possible states of tubulin to a specific classical state—objective reduction (OR). 

Each collapse is defined as a moment of consciousness.  These moments of consciousness summate to form conscious experience.

There are two open questions in this model. 
1. Since microtubules are in every eukarotic cell, including other animals, plants and fungi.  Are all animals, plants and fungi also conscious?

2. How does this model explain why certain brain areas are more connected with consciousness than others?

Next we look at Quantum Effects in the synapse.

Action potentials are an all-or-none event after leaving the axon hillock. However, exocytosis, which passes on the action potential, occurs with a probability around 0.25.  Being probabilistic rather than deterministic, synaptic dynamics may be quantum mechanical in nature.

Beck and Eccles suggest that neurotransmittor vesicles form a presynaptic vesicular grid at the axon terminal.  Exocytosis involves only one vesicle emitting transmitter molecules into the synaptic cleft—while others are blocked.  These authors suggest that prior to one vesicle firing, all vesicles are in a quantum superimposition of firing and not firing and selection of a specific vesicle may reflect shifting of quantum probability amplitudes

Beck and Eccles propose a dualistic model with the mind momentarily increasing the probability of exocytosis in selected synapses to bias a specific circuit firing.

Stapp also discusses quantum events in the synapse but emphasizes the dynamics of calcium control of vesicle activity during exocytosis.
He observes that calcium ion channels that initiate exocytosis are extremely narrow—about as wide as the calcium ion itself or one nanometer wide. This constrains the lateral dispersion or spreading of the ion wave.  The large quantum uncertainty at the individual calcium ion channel, according to Stapp, represents a quantum mixture of many classical states, each associated with a specific classical experience. 

Stapp also proposes a dual nature of mind and brain and suggests that the mind tips the quantum states into a specific classical experience, or a “template for action.”

There are three open questions in these synaptic models.

  1. How does the mind know which synapses to change to bias consciousness experience?
  2. How does this model explain why certain brain areas are more connected with consciousness than others?
  3. Both models appear to push the mind/body question deeper into the system—but leaving the essential question unanswered: How does the mind interact with the body? and what is the relation between the mind and the quantum processes at the synapse?

These first two models describe quantum events at the level of molecules—10-8 m and smaller.  To affect human experience, quantum events need to be active at macroscopic levels. 
Quantum tunneling is a microscopic quantum event that occurs at macroscopic levels.

Isolated cellular quantum states could spread macroscopically via quantum tunneling through gap junctions, which are primitive electronic windows between dendrites and dendrites and between dendrites and glial cells.
Kandel proposes that cells interconnected by gap junctions form networks which fire synchronously, "behaving like one giant neuron", and possibly account for synchronized neural activity such as coherent 40 Hz EEG , which is connected with conscious experience.

Gap junctions are most prevalent in the cortex, thalamus and RAS, brain areas that Edelman labels as the Dynamic Core
These areas are critical for conscious experience. For instance, a lesion in the intralaminar nuclei of the thalamus produces permanent coma.
The dynamic core is hierarchically structured and functions recursively to generate conceptual content by integrating perceptual and motor signals with stored memories. 

The quantum states produced at the level of microtubules and synapses may spread through these gap junctions in the dynamic core enabling brain-wide quantum states.

How do these considerations relate to consciousness and consciousness experience?
1st We are born with our brain unassembled.  So a model of brain and consciousness needs to explain how brain circuits are created in development.
Neuroscience explains that natural maturation interacting with experience creates the brain circuits through which we experience the world.
Natural maturation is driven by biological intelligence—it is in the DNA

External experience shapes which connections are maintained and enriched.
Edelman’s model of Neural Darwinism describes these two processes as developmental selection, increasing and decreasing synaptic connections and myelination, and experiential selection—effects of experience on selectively strengthening different connections.

Second key concept in Edelman’s model is the concept of re-entry circuits—Re-entry is the continual signaling from one brain region (or map) to another and back again across massively parallel fibers (axons) that are found in higher cortical areas and throughout the dynamic core.” Edelman

Re-enry circuits are critical for maintaining a brain state for 100s of milliseconds or more to lead to conscious perception of objects and affect an organized response.  

2nd point concerns thalamocortical neuroanatomy
The thalamus and cortex are functionally coupled by re-entrant circuits modulated by intrinsic electrical properties of the thalamocortical neurons. 
Thalamo-cortical fibers convey to the cortex the current picture of the world, while cortico-thalamic fibers convey proposed additions and revisions to this picture. The constant feed forward and feed back integrates intention and current experience.

3RD There are two parallel re-entrant thalamo cortical circuits (Jones.) Those involving thalamic core nuclei and those involving thalamic matrix nuclei.

Core nuclei are spatially distinct and include specific sensory and motor thalamic nuclei.  A period of sustained hypopolarization results in a well-defined re-entrant activation pattern with extensive corticothalamic recurrence and temporal binding properties, to create the complex combined sensory- motor landscape of individual experience.
A footnote here, I think the information is not in the thalamocortical circuits themselves, but in the large scale integration that they maintain through their recursive firing.

The matrix cells are dispersed throughout the thalamus.  They fire diffusely up to layer I.  Neurons in all cortical layers, except for layer IV, have their distal processes in layer I.  Thus, modulation of arousal levels of all cortical neurons can be controlled from input to Layer I.  The matrix reentrant circuit modulates wakefulness or alertness

4TH   I suggest that the core and matrix thalamocortical systems are parallel systems.  Thalamocortical circuits via core nuclei are driven by tasks and conditions and are responsible for content of experience.

Thalamocortical circuits via matrix nuclei are driven by circadian rhythm, brainstem activation and emotional value and may be responsible for subjectivity or qualia.

As core reentrant circuits need to persist for 100s of msec to sustain objective experience,
so matrix reentrant circuits may need to persist for 100s msec to sustain sense of self, and determine the qualia of the experience.

Contents of consciousness change with each re-direction of attention and so dynamics in core re-entry circuits may rapidly change.  In contrast, qualia or self-awareness would need to be more resistant to change to provide a stable background to integrate sensory input.

5th point is that conscious experience is the resonance between these two parallel thalamocortical circuits.

Gamma EEG is considered the mark of core reentrant circuits that provide sensory information. Alpha EEG is considered by some  researchers to be the mark of matrix reentrant circuits that give self awareness.

The combination of these two circuits is suggested by Palva and Palva’s work that reports greater cross frequency coherence between these two frequency bands with increasing difficulty of task processing—demanding the stronger connection  between inner awareness and task proesses.

 

Meditation practices may be considered scientific probes to explore these two proposed circuits

Meditation can be seen to fall on a range of cognitive control.

With meditations in the focused attention category involve high control of mental content. 
Meditations in the open monitoring category allow experiences to pass through awareness without manipulation, control or analysis.  They do however maintain the act of watching or passive observation of experience.
Meditations in Automatic Self-transcending involve systematic reduction of the procedure of meditation.  They involve transcending of control, processing and mental content.

In transcending…contents become secondary as core reentry circuits appear to be dampened and inner subjectivity becomes more primary as matrix reenty circuits become self sustaining ….many times in meditations in this category all contents are transcended and pure consciousness is experienced.

What is pure consciousness? When content is reduced, what is left to experience?  From them…..

Absence of time, space and body sense, but self-awareness is maintained.

This may be the experience of matrix reentry circuits maintaining continuous firing through the meditation procedure.  Since there is minimal external content, the content of the experience becomes wakefulness itself.

During pure consciousness experiences see high alpha coherence It is symmetric left and right and anterior/posterior.  There is little gamma coherence during these meditation because the process is automatic.

Note: This Alpha coh is also synchronous…create a standing wave on the scalp.  Russell Hebert will be discussing the significance of alpha standing waves and meditation experiences at tomorrow night’s concurrent session, Wed NCC II #12.……

7th point of this model
In discussing the dynamic core, it was suggested that the quantum states produced at the level of microtubules and synapses may spread through these gap junctions in the dynamic core leading to brain-wide quantum states.
Speculation:
The experience of pure consciousness might be the experience of quickly changing quantum states produced at the level of microtubules and synapses that spread through gap junctions to support activity within matrix reentry circuits.  Quantum dynamism might be appreciated as a state of wakefulness, alertness without content—“no  thing”—during  this experience.

Any questions?