ABSTRACT
318 319The brain is a hierarchical system which extends below the level of neurons and synapses to intra-neuronal processes. Complex symphonies of molecular activities, these processes determine neuronal architecture, synaptic function and plasticity, and are orchestrated and controlled by the cytoskeleton. Networks of protein polymers which include microtubules (“MT”), actin, intermediate filaments, and centrioles, the cytoskeleton is a dynamic scaffolding in which microtubule-associated proteins (“MAPs”) cross-link MT, other cytoskeletal structures, organelles, membranes and receptors. Linked to external events by membrane receptors, structural proteins, ion fluxes, second messengers and protein kinases, cytoskeletal activities can provide a cognitive substrate in cells ranging from single-cell organisms such as Paramecium to human cortical neurons. We propose a set of models for computing within MT and cross-bridging MAPs in which signals and information are represented and transmitted via propagated quantum dipole-coupled conformational changes of these structures' subunits which locally interact via “cellular automata-like” transitions. Cytoskeletal automata (based on quantum dipole-coupled, coherent 10−9 to 10−11 sec protein subunit conformational excitations) may recognize and adapt to neuronal membrane and synaptic events by changing conformational patterns, modifying MAP-MT connections (and thus neural architecture and synaptic function) and retrograde signaling. These cytoskeletal functions may subserve dendritic processing in neuronal ensembles, provide feedback signaling analogous to back-error propagation in artificial neural networks, link neuronal processes to quantum effects and provide a molecular substrate for cognition.
