Toward a charge-transfer model of neuromolecular computing

Abstract

A computational model of charge transfer through an associated polyenic system is presented. This model is based on proposed transient alignment of adjacent ethylenes of phospholipid diacyls in the neural membrane. Influx of anions and cations into the cytosol at ∼108 ions/s at ligand-gated channels hypothetically establishes the conditions for charge transfer through adjacent diacyl ethylenes. It is suggested that this process produces interactions between phospholipid potential energy hypersurfaces. These interactions operating in many-dimensional (Hilbert) space represent a form of massively parallel computation. Basic theoretical principles of quantum computing relevant to the present model are briefly discussed. A preliminary computational model of charge transfer through stacked ethylenes is then presented. In this model molecules were aligned with planes parallel and perpendicular. Singly charged counterions were positioned at the ends of the stacks and ab initio Hartree–Fock calculations at the 6-31+G(d, p) level were carried out. Degree of charge transfer between counterions was monitored by Mulliken population analysis from which atomic charges and dipole moments were calculated. The results of these calculations are interpreted in a larger neurobiological context. Models are proposed which relate the charge-transfer process to ion channel dynamics (open/closed), changes in membrane potential, and macroscopic memory systems. A hypothetical feedback circuitry which could regulate membrane potential and prevent recurrent excitation or hyperpolarization is described. Potential tests of the model utilizing photoinduced charge transfer through a polyenic molecular wire are proposed. It is concluded that this research could lead to a better understanding of computational processes in neurophysiology and cognition. © 1998 John Wiley & Sons, Inc. Int J Quant Chem 69: 3–10, 1998