Adaptation of eye and hand movements to target displacements of different size

Abstract

Previous work has documented that the direction of eye and hand movements can be adaptively modified using the double-step paradigm. Here we report that both motor systems adapt not only to small direction steps (5° gaze angle) but also to large ones (28° gaze angle). However, the magnitude of adaptation did not increase with step size, and the relative magnitude of adaptation therefore decreased from 67% with small steps to 15% with large steps. This decreasing efficiency of adaptation may reflect the participation of directionally selective neural circuits in double-step adaptation.

Interference between adaptation to double steps and adaptation to rotated feedback in spite of differences in directional selectivity

“…As during the use of a computer mouse, the hand was not concealed from view. This arrangement was similar to those of other studies, which reported robust and persisting adaptation Grigorova et al 2013;Schmitz et al 2010Schmitz et al , 2012.…”

“…Thus, the results are valid for such spacing, only. As shown for adaptation to rotated feedback and to double steps, generalization decreases with increasing target spacing and target steps (Bock and Schmitz 2011;Schmitz et al 2010). Future studies should investigate width and shaping of spatial generalization in relation to visual input and motor performance by varying the target spacing and the size of the sensorimotor discordance.…”

“…1). A target spacing of 45° had been chosen to enhance the comparability to earlier studies on directional selectivity of adaptation to rotated feedback (Bock and Schmitz 2011;Krakauer et al 2000) and to double steps (Schmitz et al 2010) as well as to a study that had investigated transfer between both adaptation methods (Schmitz et al 2012). Targets disappeared when they had been reached by a cursor of 0.5 cm radius for a cumulative time of 750 ms. During movements without cursor feedback, targets disappeared after a constant interval of 3000 ms. Motion of the screen cursor was metrically equivalent to the motion of the stylus on the tablet.…”

“…Therefore, and to enhance the comparability of the present study to former studies (Borisova et al 2014;Bock and Schmitz 2011;Grigorova et al 2013;Heuer and Hegele 2011;Schmitz et al 2010Schmitz et al , 2012, the analysis primarily focused on initial movement directions. Movement onset and movement end were defined as the points in time when the movement velocity exceeded 25 mm/s or decreased below 15 mm/s.…”

“…However, doublestep adaptation proceeds slower and is less complete than adaptation to rotated feedback (Schmitz et al 2012), and subjects can only adapt to small double-step sizes (Schmitz et al 2010), but to larger feedback rotations (e.g., Abeele and Bock 2001). As shown in Fig.…”