MT Automata Holography Hameroff Watt Smith

The self-focusing of electromagnetic energy described by the Milan group is thought to occur by an electret induced increase in the refractive index of cytoplasm. A similar concept was proposed (Hameroff, 1974) in which microtubules were thought to act like "dielectric waveguides" for electromagnetic photons. Living tissue does transmit light more readily than nonliving material. Van Brunt, Shepherd, Wall, Ganong and Clegg (1964) measured penetration of sunlight into mammalian brain by routes other than the visual system. Stereotactically placed photoreceptors recorded intensities of 10-3 lumens in sheep hypothalamus when surface intensity was 0.4 lumens, with a logarithmic diminution. The most light permeable areas were in the temporal regions of the skull, lateral to the orbits; the brain's temporal poles and hippocampus received maximum light intensity. When the animals were sacrificed, light penetration to the hypothalamus remained constant for about 30 minutes following which the brain opacity rose sharply. This suggests that some property of living brain tissue is relatively translucent to optical photons; polymerized MT acting as waveguides may be such a property.

Hameroff (1974) also proposed that the periodic array of MT subunits "leaked," or diffracted energy with 8 nanometer periodicity, resulting in a source of "coherent" energy (or calcium ions) from each MT. Cytoplasmic interference of the coherent sources from among multiple MT would lead to holographic imaging in cytoplasm. Coupling of calcium concentrations to cytoplasmic sol-gel states could "hardwire" holographic patterns into the microtrabecular lattice. In parallel arrays of MT within nerve fibers, graded potentials or traveling action potentials were thought to collectively activate "planes" of cytoplasm perpendicular to the long axis of the MT and nerve fibers. These traveling planes may be likened to image screens as in TV sets. In a TV picture tube, the screen is motionless and electron beams move to create a picture by their intersection with the screen. Perhaps imaging within neurons occurs on traveling screens generated by action potentials moving through parallel MT arrays. The content of such images would depend on programming mechanisms in the conformation of tubulin subunits which comprise the MT walls and which update with each successive action potential. Hameroff and Watt (1982) described a method of MT tubulin programming in which charge carriers (calcium ions, electrosolitons) or conformational waves such as phonons or solitons were steered through MT lattices by genetically or cytoplasmically programmed tubulins and specific MAP binding sites. MAP bridges to other MT, cytoskeleton, or other organelles were thought to act as "sinks" or "sources" which conveyed pulse trains of charge/conformation among MT throughout the cytoskeleton as a regulatory and communicative medium. Hameroff and Watt (1982, 1983) likened MT to microprocessors in which switching in a "Boolean matrix" was determined by programming factors intrinsic to the tubulin subunits (Figure 8.9).

Figure 8.8: Interference patterns in cytoplasm caused by coherent waves (e.g. Ca++, sol-gel state, MTL) generated by dynamic activities in microtubules may be a basis for holographic information imagery.

Figure 8.8: Interference patterns in cytoplasm caused by coherent waves (e.g. Ca++, sol-gel state, MTL) generated by dynamic activities in microtubules may be a basis for holographic information imagery.

Figure 8.9: Boolean switching matrix in microtubule lattice from Hameroff and Watt (1982). Alpha and beta tubulin subunits in the MT lattice wall were considered to be transiently occupied by quanta of charge/energy/conformation. MAPs behaved as "left switches" or "sink" or "source" proteins. Sequences and patterns of conformational states traveled through the MT lattice and via "sink" and "source" inter-MT bridges throughout the cytoskeleton somewhat like a pinball machine. The model demonstrated a capability for tubulin-MAP "programming" of dynamic activities related to biological intelligence.

Figure 8.9: Boolean switching matrix in microtubule lattice from Hameroff and Watt (1982). Alpha and beta tubulin subunits in the MT lattice wall were considered to be transiently occupied by quanta of charge/energy/conformation. MAPs behaved as "left switches" or "sink" or "source" proteins. Sequences and patterns of conformational states traveled through the MT lattice and via "sink" and "source" inter-MT bridges throughout the cytoskeleton somewhat like a pinball machine. The model demonstrated a capability for tubulin-MAP "programming" of dynamic activities related to biological intelligence.

In subsequent papers, Hameroff, Smith and Watt (1984, 1986) utilized principles of cellular automata to explain information processing in MT. As described in Chapter 1, cellular automata are dynamical systems which can generate and process patterns and information, and are capable of computing. Cellular automata require a lattice structure of "like" neighbors with discrete states and neighbor rules, and a universal "clock" to which all neighbors are timed. Adopting Fröhlich's model of coherent nanosecond dipole oscillations coupled to conformational states as a clocking mechanism, the authors calculated MT lattice neighbor Van der Waals dipole interactions as rules for an MT-automaton computer simulation. Each tubulin dimer was considered to be in one of two possible states at each nanosecond "generation." The two states were related to Fröhlich's concept of dipole oscillation so that the dipole can be oriented either toward the alpha tubulin end ("a," Figure 8.2.13) or toward the beta tubulin end (represented by a dot in the Figure). The polarity and electret behavior of MT indicate that in the resting state, tubulin dimer dipoles should be oriented toward the beta monomer.

Dimer states at each "clock tick," or generation were determined by neighbor states at the previous generation.

n n state = a, if £ f (y) > 0, state = p, if £ f (y) < 0, i=1 i=1

where n = 7 as the number of neighbors, and f(y) the force from the "ith" neighbor in the y direction.

The dipole state of any particular dimer at each clock tick thus depends on the summation of the dimer's neighbor dipole states (including its own) at the previous clock tick. The neighbor influences are unequal because of the screw symmetry of the MT lattice. Distant dimers (more than one neighbor away) would be expected to have little influence because of the dropoff in force intensity (y/r3) with distance. However, collective influences from many "like" oriented dimers could lead to long range cooperativity. Using only near neighbor influences, computer simulation of an MT automaton yielded interesting patterns and behavior of dipole/conformational states. These included both stable and traveling interactive patterns capable of computing and regulation of cytoskeletal activities. For example, Figure 8.13 shows a "kink-like" pattern traveling through an MT lattice, leaving an altered "wake," or memory. Assuming nanosecond generations, these traveling patterns would travel at 8 nanometers per nanosecond (80 meters per second), a velocity consistent with propagating action potentials, or solitons. Variability in individual tubulin dimer isozymes, ligand bind-ing, or MAP attachments could "program" and "read out" information in routine cellular functions. As one example, propagation of MT conformational patterns could coordinate the activities of contractile MAP sidearms in axoplasmic transport. In a general sense, MT automata may be the information substrate for biological activities ranging from ciliary bending to human consciousness. Specific automata patterns distributed throughout wide volumes of cytoskeletal arrays within the brain could lead to cooperative resonance and collective effects resulting in a thought or idea similar to the manner in which coherence induced phase transitions in metals yield emergent collective properties such as superconductivity.

Figure 8.10: Top: MT-tubulin dimer subunits comprised of a and b monomers. Relative electron occupancy of either monomer may correlate with coherent dipole oscillations in the nanosecond time domain. Bottom: screw symmetry hexagonal packing leads to unequal neighbor rules based on lattice distances and Van der Waals dipole interactions. For dimers shown at right, x = 5 nm, y = 4 nm, r = 6.4 nm. The relative strength of each neighbor dimer dipole state is y/r3.

Figure 8.10: Top: MT-tubulin dimer subunits comprised of a and b monomers. Relative electron occupancy of either monomer may correlate with coherent dipole oscillations in the nanosecond time domain. Bottom: screw symmetry hexagonal packing leads to unequal neighbor rules based on lattice distances and Van der Waals dipole interactions. For dimers shown at right, x = 5 nm, y = 4 nm, r = 6.4 nm. The relative strength of each neighbor dimer dipole state is y/r3.

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