Adaptation of saccadic eye movements involves different coordinate systems
56.518, Tuesday, May 14, 2:45 - 6:45 pm, Vista Ballroom
Delphine Lévy-Bencheton1, Denis Pélisson1, Muriel Panouillères1, Christian Urquizar1, Caroline Tilikete1,2, Laure Pisella1; 1CRNL Inserm U1028 UMR5292, 2Hôpital Neurologique Pierre Wertheimer - Neuro-ophthalmology department
Saccadic adaptation allows changes of saccade over time after repeated post-saccadic error (McLaughlin, 1967). Adaptation is known to occur in oculocentric coordinates and to be unidirectional: adaptation of rightward saccades does not transfer to leftward saccades. However, Zimmermann et al. (2011) proposed that adaptation can unfold in spatiotopic coordinates: outward adaptation of rightward scanning saccades transferred to all memory-guided double-saccades (including those performed in the non-adapted direction) such that their endpoint shifted rightward (as if the visual target was re-localized). But the authors questioned whether their subjects could have used the visible frame of the computer screen as a reference, thus allowing adaptation in allocentric -rather than in spatiotopic- coordinates. In the present study, we re-assessed this question by using targets LEDs presented in complete darkness to avoid any visual reference. Nine subjects performed the paradigm of Zimmermann et al. (2011) in this no-frame condition and in a frame condition, in two separate sessions. Repeated measures ANOVA (factors: frame/no-frame and pre/post) performed on the amplitude of leftward memory-guided double-saccades revealed a significant decrease after adaptation only when a frame was provided (interaction p<0.01), in agreement with the allocentric hypothesis of adaptation. Note however that the remapping processes which encode the parameters of the second saccade in this double-saccade task may have favored allocentric adaptation. Indeed, by testing memory-guided single-saccades after adaptation of rightward scanning saccades, we found a main effect of phase (p=0.026) but no interaction with the frame versus no frame conditions. This indicated that leftward memory-guided single-saccades significantly decreased after adaptation, with or without the frame, in agreement with spatiotopic adaptation. A last experiment testing the effect of the same adaptation on immediate single-saccades revealed oculocentric adaptation. Taken together, these three experiments indicate that the same saccadic adaptation can involve allocentric, spatiotopic and oculocentric coordinates.