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Sensorimotor adaptation of size perception.

26.3002, Saturday, 16-May, 2:45 pm - 6:45 pm, Banyan Breezeway
Session: Eye Movements: Perception and neural mechanisms

Cécile Eymond1, Céline Paeye1, Marianne Duyck1, Patrick Cavanagh1, Thérèse Collins1; 1Laboratoire Psychologie de la Perception, Université Paris Descartes, CNRS UMR 8242

Sensorimotor adaptation is the process by which new associations between movements and their perceptual effects are learned. Previous work reported that the visual system learns associations between peripheral (coarse) and foveal (highly defined) images of objects to achieve feature constancy across eye movements (e.g., Cox et al., 2005). Here we investigated the ability to learn perceptual associations between peripheral and foveal object size across saccades. In a pre-adaptation phase, participants made saccades to a peripheral disk. During these saccades this disk was replaced with a bigger or smaller disk. Participants had to decide whether the post-saccadic (foveal) disk was bigger or smaller compared to the pre-saccadic (peripheral) disk. For each participant, we defined the critical size change that led to 75% correct performance. In the following 30-min adaptation phase, subjects made saccades to the peripheral disk. During the saccade, the disk was modified by the critical size change measured individually. The post-adaptation phase was identical to the pre-adaptation phase except that adaptation trials were interleaved to maintain the level of adaptation. Preliminary results on 5 participants showed a significant shift of the PSE after adaptation in the direction of the adapted size change. For example, after adapting to a small-to-large trans-saccadic size change, the post-saccadic target had to be slightly larger than the pre-saccadic target to appear as matched in size, while objects that did not change size during the saccade were seen as slightly shrinking. This suggests that a new trans-saccadic correspondence of object size was learned and that perhaps, like the trans-saccadic correspondence of object position (saccadic adaptation), the trans-saccadic correspondence of object size and other features might be adaptable.

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