A Study of the Role of the Maintained-Discharge Parameter in the Divisive Normalization Model of V1 Neurons
چکیده
The divisive normalization model [Heeger, 1992] accounts successfully for a wide range of phenomena observed in singlecell physiological recordings from neurons in primary visual cortex (V1). Using mathematical analyses and simulation experiments, we investigated the role of the maintaineddischarge (base firing rate) parameter in this model. We developed an implementation that can take grayscale images as inputs and applied it to the types of visual stimuli used in a comprehensive suite of published physiological studies. We found that three empirical phenomena are closely associated with the maintained-discharge parameter: (A) the existence of inhibitory regions in the receptive fields of simple cells in V1, (B) the supersaturation effect in the contrast sensitivity curves, and (C) the narrowing/widening of the spatial-frequency tuning curves when the stimulus contrast decreases. The model predicts two patterns of these phenomena: One possibility is that a neuron can show A, B, and widening (C); the other possibility is to show not-A, not-B, and narrowing (C). This interdependence is a potentially falsifiable prediction of the divisive normalization model.