Nearly extensive sequential memory lifetime achieved by coupled nonlinear neurons

Many cognitive processes rely on the ability of the brain to hold sequences of events in short-term memory. Recent studies have revealed that such memory can be read out from the transient dynamics of a network of neurons. However, the memory performance of such a network in buffering past information has only been rigorously estimated in networks of linear neurons. When signal gain is kept low, so that neurons operate primarily in the linear part of their response nonlinearity, the memory lifetime is bounded by the square root of the network size. In this work, I demonstrate that it is possible to achieve a memory lifetime almost proportional to the network size, "an extensive memory lifetime", when the nonlinearity of neurons is appropriately utilized. The analysis of neural activity revealed that nonlinear dynamics prevented the accumulation of noise by partially removing noise in each time step. With this error-correcting mechanism, I demonstrate that a memory lifetime of order $N/\log N$ can be achieved.Comment: 21 pages, 5 figures, the manuscript has been accepted for publication in Neural Computatio

Evaluating mean sojourn time estimates for the M/M/1 queue

AbstractMean sojourn time is one of the most important performance measures for queueing systems. It is difficult to obtain the real sojourn time of a customer directly, so it is also difficult to estimate the mean sojourn time. In this paper, we propose a new and relatively simple estimate of the mean sojourn time in a single server queue, using the number of arrivals and the number of departures. This method can be used for evaluating the quality and the performance of call processing in communication switching systems, for example. We evaluate the accuracy of this estimate for an M/M/1 queue, using some results obtained by Jenkins. This estimate is compared with two other standard estimates of the mean sojourn time obtained from the sequence of actual arrival and departure times