How post-saccadic error information recalibrates visual space

• Applicant: Professor Dr. Eckart Zimmermann
• Subject Area: Biological Psychology and Cognitive Neuroscience
• Term: since 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 492835857

How the brain generates an accurate spatial perception of the external world is still a mystery in neuroscience. Although internal neural maps contain a topographic representation of space, a process is needed that keeps the scale of that representation in alignment with the external world. Only movement errors can quantify the accuracy of the internal representation. Due to their ballistic nature and their close link to visual perception, saccades are perfectly suited to measure the accuracy of internal maps. The aim of the current grant proposal is to investigate whether spatial perceptions remains accurate through active recalibration by post-saccadic errors. Our lab has recently reported that visual and motor localization is serially dependent on the error size of saccades that were performed in the previous trial. Five experiments are described in the grant proposal that shall test a model of active recalibration which suggests that every saccade leads to a recalibration of internal space maps. In contrast to previous models which suggested a shared resource between motor and visual space, in active recalibration motor and visual spatial processing remain separate but are both recalibrated by post-saccadic errors. The proposed neural mechanism is in agreement with recently reported post-saccadic error processing in posterior parietal cortex. The experiments of this grant proposal are designed to test whether visual localization is guided by a shared resource between visual and motor space or active recalibration. They shall test the proposed neural mechanism of active recalibration. To this end, the experiments shall reveal through which signal the post-saccadic error is sensed by the sensorimotor system. Using masking procedures, they will measure the time-course of post-saccadic error availability for recalibration. Given the existence of separate neural areas controlling saccades, there is in principle no reason why recalibration should rely only on a single neural area. Testing recalibration after reactive and voluntary saccades, experiments will find out whether exogenously and endogenously attended stimuli are processed differently. Recalibrating spatial coordinates after every post-saccadic error can lead to distortions if errors are produced by impairments like muscle fatigue. Experiments will also address whether the sensorimotor system is capable of differentiating between errors that are due to localization inaccuracies and errors that are due to impairments. In total, the experiments will investigate a possible mechanism that keeps spatial neural maps accurate and aligned.

• DFG Programme: Research Grants