Complex cells as linear mechanisms receiving sequential afferents.

Abstract

Complex cells in mammalian visual cortex appear to be non-linear mechanisms lacking a structured receptive field, and different complex cells display mutually inconsistent behaviors. Current models postulate nonlinear interactions among multiple simultaneous afferents, but none explains the diversity of complex cell behaviors. We propose that complex cell inputs are sequential and cyclic. Cells receiving such input behave as if their spatial receptive field changes shape over time. Different putative time-varying receptive fields arise when the number of afferents, their characteristics and/or the sequence of their inputs vary, and simulations show that they exhibit all reported varieties of complex cell behavior. Our results suggest a common functional description for simple and complex cells. Additional non-linearities are unnecessary to explain complex cell behavior.