Are Microtubules Quantum Computers?
Interiors of neurons and glia are functionally organized by webs of protein polymersthe cytoskeleton14. Its major components are microtubules, actin and intermediate filaments. Microtubules are selfassembling hollow cylinders whose walls are crystalline lattices of subunit proteins known as tubulin. Evidence links the neuronal cytoskeleton to cognitive functions, and theoretical models suggest interactive microtubule subunits function as molecular automata capable of nanosecond-scale computation (Figure 2a)4. Figure 2. Schematic of neural synapse showing cytoskeletal structures within two neurons. Left: Pre-synaptic axon terminals releases neurotransmitter vesicles (black spheres) into synaptic cleft. Thick, black rod-like structures at top indicate microtubules; thinner filaments (e.g. synapsin) facilitate vesicle release. Right: Dendrite on post-synaptic neuron with two dendritic spines. Microtubules in main dendrite are interconnected by microtubule-associated proteins. Other cytos