Post-saccadic updating of visual space in the posterior parietal
cortex in humans
C. Bellebaum, K.-P Hoffmann. & I. Daum
Behav. Brain Res. 463:194-203, 2005
- Updating of visual space takes place in the posterior parietal cortex to guarantee spatial constancy across
eye movements. However, the timing of updating with respect to saccadic eye movements remains a matter of debate.
In the present study, event-related potentials (ERPs) were recorded in 15 volunteers during a saccadic double-step
task to elucidate the time course of the updating process. In the experimental condition updating of visual space
was required, because both saccade targets had already disappeared before the first saccade was executed. A similar
task without updating requirements served as control condition. ERP analysis revealed a significantly larger slow
positive wave in the retino-spatial dissonance condition compared to the control condition, starting between 150
and 200 ms after first saccade onset. Source analysis showed an asymmetry with respect to the direction of the
first saccade. Whereas the source was restricted to the right PPC in trials with leftward first saccades, left
and right PPC were involved in rightward trials. The results of the present study suggest that updating of visual
space in a saccadic double-step task occurs not earlier than 150 ms after the onset of the first saccade. We conclude
that extraretinal information about the first saccade is integrated with motor information about the second saccade
in the inter-saccade interval.
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