Patrick Cavanagh – 15 novembre 2018

Constructing the present in the frontal lobes

How do we know where things are? Recent results indicate that an object’s visual location is constructed at a high level where, critically, an object’s motion is discounted to recover its current location. As a result, we sometimes see a target far from its actual location. One particular target, the double-drift stimulus, develops very large illusory shifts based on an integrating time of well over a second, a duration that would encompass several eye movements during natural viewing and suggests the involvement of processes with the time course of short term memory. Indeed, these large position shifts are unaffected by saccades or smooth pursuit. I will describe how this result resurrects the long-discredited proposal that our perception of a scene is built up across saccades, including elements that are unattended. fMRI results show that the illusion does not emerge in the visual cortex but is seen in the frontal lobes, where visual-spatial short-term memory areas would have the temporal integration required to support the effect. In summary, these findings suggest that perception is a function of the frontal lobes, although where or how remains to be understood.