Remapping in LIP takes time

Despite constantly shifting our gaze, our perception remains stable. It has been proposed that receptive field (RF) remapping in the lateral intraparietal area (LIP) may play a role in maintaining spatial stability. To improve our understanding of the mechanisms underlying remapping, we investigated how the remapped response relates to saccade length. If remapping occurs by a one-step process, then we expect the remapped response to better align by saccade onset. Alternatively, if remapping occurs by a moving shift over time, then the remapped response will better align by saccade offset as longer saccades will require a greater shift, which will take more time. We recorded LIP activity in animals performing a saccade task. We confirmed neurons were in LIP using a memory guided saccade task. In most trials, animals fixated a point for 800-1050 ms and then made a visually guided saccade to a target 7, 14, or 21 degrees away. 300 ms after fixation onset, a task-irrelevant probe appeared in the post-saccadic RF and remained on throughout the trial. The saccade target appeared 500-700 ms after the probe appeared. 25% of trials were no-saccade trials, in which the animal maintained fixation and the probe appeared and remained in the neuron’s RF. 20% of trials were saccade-only trials, in which the animal made a visually guided saccade, but no probe was presented. We only include LIP neurons that exhibited a remapping response that was not driven by a motor response in the saccade-only task. In single neurons and in the population, we found that the remapped responses were better aligned by saccade offset, with the onset of the remapped response occurring later for longer saccades. This result supports the idea of a moving shift of RF during remapping and should help constrain models of remapping in parietal cortex.