Spatiotemporal Response Properties of Optic-Flow Processing Neurons

SummaryA central goal in sensory neuroscience is to fully characterize a neuron's input-output relation. However, strong nonlinearities in the responses of sensory neurons have made it difficult to develop models that generalize to arbitrary stimuli. Typically, the standard linear-nonlinear models break down when neurons exhibit stimulus-dependent modulations of their gain or selectivity. We studied these issues in optic-flow processing neurons in the fly. We found that the neurons' receptive fields are fully described by a time-varying vector field that is space-time separable. Increasing the stimulus strength, however, strongly reduces the neurons' gain and selectivity. To capture these changes in response behavior, we extended the linear-nonlinear model by a biophysically motivated gain and selectivity mechanism. We fit all model parameters directly to the data and show that the model now characterizes the neurons' input-output relation well over the full range of motion stimuli.

► The receptive fields of fly optic-flow processing neurons are space-time separable
► An increase of the motion cue density alters the neural gain and selectivity
► A biophysical model explains changes in the gain and selectivity
► This model extends the classical LN model to include selectivity and gain control