CORDIS - EU research results

Predictive Position Coding

Final Report Summary - POSITION (Predictive Position Coding)

Vision gives us enormous adaptive advantage because it allows us to see and react to events before they affect us. This predictive advantage is most obvious for an object in motion where the current trajectory often determines future location. It is equally important when the object’s motion is a result of the movement of our own eyes. Here our visual system uses knowledge about the upcoming motion of the eyes to predict the future location of the object. In this proposal, we have tracked the processes that make these predictions and the high-level maps of location on which they are represented. We focus on visual targets that are dramatically mislocalized, appearing where they are predicted to be next even though they are not yet there. We have tested these predictive processes with behavioral techniques in healthy and neurological patients, with brain imaging and with neurophysiological techniques in non-human primates.

There are “maps” of location throughout the visual system but our work demonstrates that our sense of position is constructed at a very high level. This is similar to the construction of the color we see on surfaces where the brain discounts the color of the illumination, or the way we understand people’s intentions by discounting the effect of the context on their actions. Similarly we have strong evidence for this high level construction of position which discounts our movements and the object’s movements to determine where it is now (correcting for the delays of neural transmission).

We have shown how changes in the brain due to injury (patients) or electromagnetic pulses (TMS) affect these predictive processes and we have tracked where they are occurring in brain imaging experiments on humans and behavioral and stimulation experiments on non-human primates. We have shown that there are two predictive pathways: one that drives our eye movements and uses only short term predictions and a separate one supporting perception that bases prediction on longer time scales. The different signatures of these two processes have allowed us to trace their pathways through the brain.