Guiding behavior requires the brain to make predictions about the future values of sensory inputs. Here, we show that efficient predictive computation starts at the earliest stages of the visual system. We compute how much information groups of retinal ganglion cells carry about the future state of their visual inputs and show that nearly every cell in the retina participates in a group of cells for which this predictive information is close to the physical limit set by the statistical structure of the inputs themselves. Groups of cells in the retina carry information about the future state of their own activity, and we show that this information can be compressed further and encoded by downstream predictor neurons that exhibit feature selectivity that would support predictive computations. Efficient representation of predictive information is a candidate principle that can be applied at each stage of neural computation.neural coding | retina | information theory A lmost all neural computations involve making predictions. Whether we are trying to catch prey, avoid predators, or simply move through a complex environment, the data we collect through our senses can guide our actions only to the extent that these data provide information about the future state of the world. Although it is natural to focus on the prediction of rewards (1), prediction is a much broader problem, ranging from the extrapolation of the trajectories of moving objects to the learning of abstract rules that describe the unfolding pattern of events around us (2-4). An essential aspect of the problem in all these forms is that not all features of the past carry predictive power. Because there are costs associated with representing and transmitting information, it is natural to suggest that sensory systems have optimized coding strategies to keep only a limited number of bits of information about the past, ensuring that these bits are maximally informative about the future. This principle can be applied at successive stages of signal processing, as the brain attempts to predict future patterns of neural activity. We explore these ideas in the context of the vertebrate retina, provide evidence for nearoptimal coding, and find that this performance cannot be explained by classical models of ganglion cell firing.
Coding for the Position of a Single Visual ObjectThe structure of the prediction problem depends on the structure of the world around us. In a world of completely random stimuli, for example, prediction is impossible. Consider a simple visual world such that, in the small patch of space represented by the neurons from which we record, there is just one object (a dark horizontal bar against a light background) moving along a trajectory x t . We want to construct trajectories that are predictable, but not completely; the moving object has some inertia, so that the velocities υ t are correlated across time, but is also "kicked" by unseen random forces. A mathematically tractable example (Eqs. 4 and 5 in Materials and Methods) is shown in Fig...