Anticipation of motion stimuli by contrast gain control

It is well known that retina ganglion cells encode future information of a moving bar. In this study, the authors investigate the mechanisms that give rise to the anticipation of motion. They first showed that the population response of the ganglion cells do not anticipate flashed bars, since such a stimulus is in no way predictable. However, the group activities of the cells do precede the motions of a moving bar, which is predictable. The first explanation of this would be the extrapolation performed by the retina’s spatiotemporal receptive field, yet the authors discovered that extrapolation alone does not explain the response profiles. They turned to another well-known mechanism in the retina – adaptation. The authors discovered that adaptation changes not only the response magnitude of the population, but also the shape of the population activity. Specifically, the larger the contrast, the further the retina predicts into the future. This heavily implies contrast gain control as the main mechanism for anticipation of motion. This suggests that when a high-contrast bar begins to move into the retina’s receptive field, it desensitizes the cell after some time delay. Therefore, the cell reacts most strongly when the bar enters the edge of the receptive field, but less so afterwards. The authors then built a model that incorporates contrast gain control, which matched well with experimental data (Fig 3 in the original paper). This picture further suggests that speed would be crucial to the prediction of motion, since if the bar is moving too fast, it would leave the retina with little time to adapt. Indeed, the authors then showed that the larger the speed of the stimulus, the more the population response lagged behind.

Author: Pei-Hsien Liu

Original paper: Berry, Michael J., et al. "Anticipation of moving stimuli by the retina." Nature 398.6725 (1999): 334-338.