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Masahiro Kokubu, Joost C. Dessing, J. Douglas Crawford; Hand-specificity in gaze-dependent memory-guided reach errors. Journal of Vision 2012;12(9):427. doi: https://doi.org/10.1167/12.9.427.
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Reaching movements toward remembered visual targets in a dark environment show overshoot effect relative to the gaze direction, but the exact origin of this overshoot is unknown. Because the reach errors depend on the visual target eccentricity, all previous studies (e.g., Henriques et al. 1998; McGuire & Sabes 2009) have assumed that it reflects biases in target‑related inputs to the visuomotor transformation. This possibility predicts the error pattern is hand-independent. So far, however, it has only been studied for the right hand. Here, we directly compared left and right arm reaching movements toward remembered visual targets in the dark. Right-handed subjects sat in front of a screen behind which five bicolor LEDs were attached at 0, ±10, and ±20 deg. of visual angle in a completely dark room. While fixating in the direction of a previously shown fixation LED, a red LED appeared to signal the reach target. After a memory delay of 1000 ms subjects started reaching to the remembered target position as accurately as possible (i.e., without any time pressure). They executed reaching movements with their left and right index finger alternately. Eye and hand movements were recorded using EyeLink II and Optotrak, respectively. Results so far showed gaze-dependent overshoots for both hands (P<.005). Interestingly, the effect of target eccentricity interacted with hand (P<.005), which appeared to reflect a relatively stronger overshoot effect for the left hand in the right visual field. This finding shows that the overshoot does not only reflect biases in target‑related, but also in hand-related inputs to the visuomotor transformation. This has implications for studies of reaching movements towards proprioceptive targets defined by the non-reaching hand.
Meeting abstract presented at VSS 2012
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