Journal of Biological Physics - Open Access
Follow-up paper - mathematical treatment and simulation
Marc Ebner and Stuart Hameroff
Keynote :Lecture EvoStar 2009
Several Powerpoint lectures and an abstract are below the images.
'The Conscious Pilot - Dendritic synchrony moves through the brain to mediate consciousness
Abstract for Tucson conference:
The ‘conscious pilot’: Synchronized dendritic webs move through brain neurocomputational networks to mediate consciousness
Chalmers’ ‘easy problems’ include the brain’s non-conscious abilities to discriminate and react to stimuli, integrate information, focus attention and control behavior, also expressed as ‘zombie’, or ‘auto-pilot’ modes. Chalmers’ ‘hard problem’ is the question of how the brain produces subjective conscious experience which, unlike non-conscious auto-pilot modes, is not amenable to conventional neurocomputational explanations. ‘Easy problem’ auto-pilot modes and ‘hard problem’ conscious experience are not mutually exclusive. At times, auto-pilot modes become driven by, or accompanied by, conscious experience. For example we often perform complex behaviors while daydreaming, on auto-pilot with consciousness somewhere else. But when a horn sounds or a light flashes, we consciously perceive the scene and assume conscious control. Rather than distinguishing between auto-pilot modes and consciousness, the essential distinction may be between auto-pilot modes which are, or are not, accompanied by some added fleeting feature which conveys conscious experience and choices – the ‘conscious pilot’. Consider an airplane cruising on auto-pilot. The conscious pilot is present, but not directly in control—perhaps he/she is reading a magazine, sleeping and dreaming, or chatting in the main cabin. Suddenly turbulence occurs, or an alarm sounds. The conscious pilot ‘tunes in and takes over’, directing his/her attention to the cockpit view and instrument readings, assuming control of the plane. When the situation is resolved the auto-pilot resumes monitoring and control, and the conscious pilot visits with the flight attendant. In the metaphor, the auto-pilot is the plane’s on-board flight computer and instruments. In the brain, the non-conscious auto-pilot is readily explained by neurocomputation: neuronal dendrites receive and integrate spike-mediated synaptic inputs, and when threshold is met, axonal spikes are fired as outputs. Discrete information states (‘bits’) are conveyed by axonal spikes/firings. What about conscious modes? The best measurable correlate of consciousness is gamma synchrony EEG (coherent 30 to 90 Hz field potential oscillations), occurring in various brain regions which change over time and move through the brain, or globally, e.g. cortical or thalamo-cortical gamma synchrony. The mobile synchrony correlating with consciousness is produced not by axonal spikes/firings, but via networks of neighboring neuronal dendrites connected ‘sideways’ by gap junctions (‘dendritic webs’). In computer terms, dendritic webs are laterally-connected input/integration layers embedded in feed-forward and feed-back networks. Gap junction openings and closings evolve dynamical dendritic web topologies moving throughout axonal-dendritic networks accompanied by gamma synchrony and consciousness. (Within cytoplasmic interiors of dendritic webs, the Penrose-Hameroff Orch OR model proposes quantum computations in microtubules underlie consciousness.) Gamma synchronized dendritic webs are perfectly suited to function as the brain’s ‘conscious pilot’, moving throughout neurocomputational axonal-dendritic networks, able to tune in and take over from non-conscious auto-pilot modes.