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Asya Shpiro, Ruben Moreno-Bote, John Rinzel, Nava Rubin; Noise vs. adaptation: which is responsible for perceptual switches?. Journal of Vision 2007;7(9):369. doi: 10.1167/7.9.369.
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Perceptual bi-stability occurs when the same physical stimulus gives rise to two distinct interpretations that switch in dominance irregularly. Adaptation, or fatigue processes are commonly believed to be the mechanism responsible for perceptual switches. However, noise is also known to be capable of producing alternations. The question arises, therefore, whether noise is merely a source of randomness in the switching behavior, or perhaps it plays a central role in causing alternations?
It is difficult to disentangle the effects of noise and adaptation in experiment alone, because we have no methods to control the magnitude of noise and/or adaptation independently. Mathematical models can provide insight into this question by allowing to vary these parameters at will. We performed numerical simulations in an idealized firing rate model where neuronal competition is implemented by reciprocally inhibitory populations (Shpiro et. al., J Neurophys 2007), and examined the effects of noise and adaptation parameters on the statistics of dominance durations by varying them independently
We focus on three main measures: the mean dominance duration of a percept (typically of the order of a few seconds), the CV (the ratio between the standard deviation and the mean; typically about 0.5), and the shape of distribution of dominance durations (typically, fit by gamma or log-normal functions). We sought to find regions in the noise-adaptation parameter space where computed alternation statistics are similar to those observed experimentally. We classify the switching behavior as being noise-dominated if no alternations occur in the absence of noise, and adaptation-dominated if noise is not necessary to produce alternations. Our results indicate that in order to comply with the above constraints, noise has to be the primary mechanism behind perceptual switches, while the adaptation processes are responsible for the shape of the distributions dominance durations.
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