title: Response times from ensembles of accumulators.
abstract: Decision-making is explained by psychologists through stochastic accumulator models and by neurophysiologists through the activity of neurons believed to instantiate these models. We investigated an overlooked scaling problem: How does a response time (RT) that can be explained by a single model accumulator arise from numerous, redundant accumulator neurons, each of which individually appears to explain the variability of RT? We explored this scaling problem by developing a unique ensemble model of RT, called e pluribus unum, which embodies the well-known dictum "out of many, one." We used the e pluribus unum model to analyze the RTs produced by ensembles of redundant, idiosyncratic stochastic accumulators under various termination mechanisms and accumulation rate correlations in computer simulations of ensembles of varying size. We found that predicted RT distributions are largely invariant to ensemble size if the accumulators share at least modestly correlated accumulation rates and RT is not governed by the most extreme accumulators. Under these regimes the termination times of individual accumulators was predictive of ensemble RT. We also found that the threshold measured on individual accumulators, corresponding to the firing rate of neurons measured at RT, can be invariant with RT but is equivalent to the specified model threshold only when the rate correlation is very high.
authors.affiliation: Center for Integrative and Cognitive Neuroscience, Vanderbilt Vision Research Center, Department of Psychology, Vanderbilt University, Nashville, TN 37240.
authors.forename: Bram
authors.initials: B
authors.lastname: Zandbelt
authors.forename: Braden A
authors.initials: BA
authors.lastname: Purcell
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Palmeri
authors.forename: Gordon D
authors.initials: GD
authors.lastname: Logan
authors.forename: Jeffrey D
authors.initials: JD
authors.lastname: Schall
mesh_terms: D019295:Computational Biology; D003198:Computer Simulation; D006801:Humans; D008959:Models, Neurological; D008960:Models, Psychological; D009010:Monte Carlo Method; D009474:Neurons / Q000502:physiology*; D009482:Neurophysiology; D011930:Reaction Time / Q000502:physiology*; D013269:Stochastic Processes
keywords: computational model; diffusion model; mathematical psychology; neurophysiology; reaction time