Julius B. Lucks/Bibliography/Allen-PNAS-88-1991

Notes on Allen-PNAS-88-1991

 * See also Allen-PNAS-89-1992
 * pmid: 1763012
 * design neural networks with computations achieved by single stationary state of the entire reaction
 * REFERENCES 1-14: different computational systems including digital computer, Fredkin logic gates, billiard ball collisions, cellular automata, etc.
 * "All living entities process information to varying degrees, and this can occur only by chemical means."
 * (17-18) chemical mechanisms similar to electronics
 * propose chemical reaction network that is hardware implementation of neural network
 * (15-16) coupling bistable 'flip-flop' reactions, can build universal automata
 * (19) - neural networks as a computational system
 * (11-13) - neural networks basis collective computational systems: feedforward networks, Hopfield's networks
 * propose a set of reactions that have two states, depending on the concentration of an input catalyst
 * implementation wise, to create two chemical neurons and couple them, they would need to have two independent reaction systems that obeyed the same kinetics
 * need n independent reaction systems to have n neurons
 * seems very unlikely
 * neurons communicate through activation or inhibition of another neurons catalyst that controls the state
 * system of 4 chemical reactions - write down simple ODE's for kinetics
 * conc of species A determines state of the neuron
 * conservation constraint A_i + B_i = A_o
 * conc of A and B evolve into a steady state determined by concentration of C - the chemical input parameter for the neuron
 * tune the gain of the neuron (sharpness of the jump) with rate constants k_2 and k_3
 * when couple, effect of other neurons on neuron i is encoded in C_i
 * A_i and B_i can inhibit or activate production of C_j - couple neurons this way
 * C_i can actually be the sum of many chemical entities
 * goes through constructing logic gates out of neuron i, which operates on signals from neurons j and k
 * AND - j and k activate C_i
 * OR - ja and k activate C_i, but strongly
 * A_j AND NOT A_k - j activates, k inhibits
 * A_j NOR A_k - both inhibit
 * plug in constants in the steady state concentration of C_i equation 6 to figure out if neuron i will fire
 * autonomously oscillating catalyst can act as a clock
 * all neurons updated at the same time based on current states before an impulse
 * in this architecture, 4*(N+1) distinct chemical species required for N neurons
 * each connection requires another distinct species
 * compartmentalization would reduce the number of species required
 * universal Turing machine - can do with clocked neural network of finite size and 2 infinite stacks

= References =
 * 1) Julius B. Lucks/Bibliography