Suppression of motion perception through non-linear retinal processing G Greene1, E Ehrhardt1, T Gollisch2, T Wachtler1 |
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1Department Biologie II, Ludwig-Maximilians-Universität München, Germany |
| Fixational eye movements shift the visual image across the retina during fixation. These movements can be well above thresholds for visual motion detection, yet produce little or no motion percept. This implies the existence of mechanisms for inhibition of motion signals due to eye movements. We describe a model in which such perceptual suppression can arise as a result of non-linear processing in Parasol-type retinal ganglion cells. These cells implement a non-linear spatial integration, corresponding to individual rectification of bipolar cells within their dendritic field (Hochstein & Shapley, 1976). Due to their highly transient, phase invariant spiking, these cells seem well adapted to signal motion onset and saccades. The model uses these cells as input to a motion detection mechanism which distinguishes between local and non-local motion at the retinal level. When tested with stimuli containing both local differential motion of an object against background, and global shifts of the stimulus which mimic micro-saccades, this model successfully suppresses detection of saccadic movements, while still enabling accurate tracking of object motion. Thus, the model can account for the inhibition of motion percepts arising from global shifts due to eye movements, even in the absence of any reliable information about eye position. |
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