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Therese Gilligan, Filipe Cristino, Robert Rafal, Janet Bultitude; Still seeing straight: No role for ocular proprioception in prism adaptation? . Journal of Vision 2016;16(12):535. doi: https://doi.org/10.1167/16.12.535.
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© ARVO (1962-2015); The Authors (2016-present)
Reaching toward a visual target displaced by laterally refracting prisms results in adaptation of limb proprioception and a visual shift, which individually and additively lead to prism adaptation (PA). The visual shift is hypothesised to be due to recalibration of neural signals encoding the straight ahead eye position in the orbit; itself hypothesised to be a result of error correction during PA, and to a contribution from 'eye muscle potentiation' (EMP) – a resetting of ocular straight ahead following sustained lateral gaze. This research is the first to directly investigate the contribution of ocular proprioception to PA by measuring eye position before, during, and after PA and also before, during, and after a condition in which gaze was shifted but no visual feedback of pointing errors were available (eye muscle proprioception; EMP). We also recorded measures of limb proprioception (straight-ahead pointing with eyes closed; SAP) and measures of combined ocular and limb proprioception (open-loop pointing; OLP) using eye tracking and touchscreen systems. Consistent with previous research, healthy participants (n=17) showed larger after-effects in OLP than SAP, after PA but not after EMP, consistent with the idea that PA results in a shift in the representation of visual targets. However, contrary to our hypothesis, there was a change in straight-ahead ocular fixation following the EMP condition, but not after PA. One interpretation of these results is that the PA-induced visual shift in the location of targets is not the direct result of recalibration of eye position in the orbit but may be more exclusively the result of adapted limb proprioception and a change in proprioceptive-spatial mapping against visuo-spatial mapping.
Meeting abstract presented at VSS 2016
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