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Constanze Schmitt, Milosz Krala, Frank Bremmer; Neural correlates of path integration during visually simulated self-motion. Journal of Vision 2019;19(10):236b. doi: https://doi.org/10.1167/19.10.236b.
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Navigation through an environment requires knowledge not only about one’s direction of self-motion (heading), but also about traveled distance (path integration). We have shown before (e.g. Churan et al., J. Neurophysiol., 2017) that visual optic flow can be used to reproduce the distance of a previously perceived self-motion. In our current study, we employed EEG in human participants to identify neural correlates of such path integration behavior. Visual stimuli were presented on a computer monitor (42° * 24°) 68 cm in front of our participants and simulated self-motion across a ground plane. Stimuli were presented in one of three conditions: passive, active and replay. First, we presented a simulated forward self-motion (passive). Then, participants were asked to use a gamepad to reproduce double the previously observed travel distance (active). Third, the resulting visual stimulus from the active condition was recorded and, after three of such passive-active pairs, played-back in random order to our participants, but without an additional behavioral task (replay). Participants fixated a central target during all stimulus presentations. When aligning event related potentials (ERPs) to visual motion on- or offset, we found attenuated responses in the active condition as compared to the replay and passive condition. These differences were expected in the framework of predictive coding. We then aligned EEG data from the active condition on a trial-by-trial basis to the point in time, when the participants had reproduced half of their travel distance (subjective single distance). In about half of the participants, a wavelet based time-frequency analysis revealed an enhancement in the alpha band around this time-point on central and parietal midline electrodes. No such peak was observed when aligning data to the real, i.e. objective single distance. We consider this activation a neural marker for subjective spatial position and path integration during visually simulated self-motion.
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