Introduction 1996 1985 1987 1988 1989 1992 1989 1992 1994 1994 1995 1 Fig. 1 left White gray circles  1994 1995 1996 1998 2000 1989 2000 1985 2000 2001 2002 1979 2000 2001 2002 1999 1979 1994 2005 2005 1990 1985 2005 2005 2000 Methods Participants 1971 Apparatus 2 Fig. 2 Upper panel Lower panel white circles  2 2 2 The rack with armrest and manipulandum could be positioned in different orientations with respect to the LED bow, allowing manipulation of wrist posture (see below). Each rack orientation was calibrated to the LED bow to facilitate direct comparison of target and feedback signals as well as for offline comparison of target signal and potentiometer data (both expressed in °). Point-of-gaze was expressed in °, allowing for a comparison of point-of-gaze and the target signal. Eye-tracker data were synchronized with potentiometer and LED bow data. Procedure 1998 2005 3 3 Fig. 3 rectangles  3 Data analysis −5  Pre-processing Potentiometer data (hand movement) and LED coordinates (target) of the included trials were transformed into ° and low-pass filtered using a bi-directional second-order Butterworth filter (cut-off frequency: 15 Hz). The first five cycles of each trial were excluded from analysis to eliminate possible transient effects. From the remaining 31 cycles several dependent variables were calculated. Those variables related to tracking performance, anchoring, and global kinematics, respectively. Tracking performance 1972 Anchoring 1 1994 1995 2000 2005 2007 \documentclass[12pt]{minimal}
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$$ {\text{AI}} = \frac{{{\text{SD}}_{l} }} {{{\text{SD}}_{l} + {\text{SD}}_{r} }}, $$\end{document} l r l r spatial temporal 1 Global kinematics \documentclass[12pt]{minimal}
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$$ {\text{MDI}} = \frac{{{\text{MD}}_{{{\text{flexion}}}} }} {{{\text{MD}}_{{{\text{flexion}}}} {\text{ + MD}}_{{{\text{extension}}}} }}, $$\end{document} flexion extension flexion extension flexion extension \documentclass[12pt]{minimal}
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$$ {\text{PVI}} = \frac{{{\text{PV}}_{{{\text{flexion}}}} }} {{{\text{PV}}_{{{\text{flexion}}}} + {\text{PV}}_{{{\text{extension}}}} }}. $$\end{document} flexion extension r 2 r 2 r 2 1999 1988 Statistical analysis P \documentclass[12pt]{minimal}
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\begin{document}$$ (\eta ^{2}_{p} ). $$\end{document} t t spatial temporal  Results Effects of wrist posture spatial temporal 1 Table 1 Results of the repeated measures ANOVA on dependent variables Dependent variable Wrist posture Gaze direction Posture × gaze F P \documentclass[12pt]{minimal}
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\begin{document}$$ \eta ^{2}_{p} $$\end{document} RMS 1.67 NS 0.13 0.60 NS 0.05 1.85 NS 0.14 ϕ 0.49 NS  0.04 9.46 <0.005 0.46 0.84 NS 0.07 TCV 4.38 <0.05 0.28 1.39 NS  0.11 1.20 NS 0.10 spatial 36.10 <0.001 0.77 81.60 <0.001 0.88 0.39 NS 0.03 temporal 32.55 <0.001 0.75 0.26 NS  0.02 1.39 NS 0.11 PVI 48.25 <0.001 0.81 13.11 <0.001 0.54 1.45 NS 0.12 MDI 41.73 <0.001 0.79 14.79 <0.001 0.57 1.55 NS 0.12 NL 7.09 <0.005 0.39 3.13 NS  0.22 1.73 NS 0.14 Main effects of wrist posture and gaze direction and wrist posture × gaze direction interaction effects are presented RMS ϕ TCV AI spatial AI temporal PVI MDI NL spatial temporal 4 t spatial temporal t P t P t P t P Fig. 4 left panels right panels Asterisks Error bars  5 1 t t P t P t P t P Fig. 5 left panel right panel vertical dashed line  6 1 Fig. 6 columns rows gray black dotted black line  Effects of gaze direction spatial temporal 1 spatial t spatial t P 4 spatial t P spatial spatial \documentclass[12pt]{minimal}
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\begin{document}$$ (\eta ^{2}_{p} = 0.88), $$\end{document} temporal 4 1 5 1 t 6 6 Wrist posture × gaze direction interaction effects 1 spatial 1 spatial 7 spatial Fig. 7 L C R Asterisks spatial Error bars  Discussion In the present experiment we sought to systematically delineate the effects of visual and musculoskeletal factors on anchoring phenomena, that is, local reductions in kinematic variability, which may reflect “organizing centers” for perceptual-motor control. In particular, we investigated the relative contributions of gaze direction and wrist posture on both spatial and temporal anchoring in the performance of a rhythmic, unimanual visuo-motor tracking task. In addition, we examined the velocity profiles and Hooke’s portraits of the full tracking trajectories to gain insight into the relationship between the local anchoring phenomena and the global organization of the tracking movements. In the following, we first outline the main findings of both types of analysis before discussing their broader implications for the theoretical understanding of anchoring. Effects on spatial and temporal anchoring  2005 4 2005 4 7 1 Effects on global tracking behavior  5 6 Those qualitative observations were reflected in significant differences in the duration, peak velocity and harmonicity of the flexion and extension phases of the movement as determined from the velocity profiles and Hooke’s portraits. Wrist posture strongly affected the global tracking behavior and led to marked differences between flexion and extension for wrist postures other than neutral. For the flexed (extended) wrist posture, the flexion (extension) phase lasted shorter, had higher peak velocity and was less harmonic than the extension (flexion) phase. Gaze direction also significantly affected movement duration and peak velocity of the flexion and extension half cycles, albeit to a much smaller degree. If gaze was directed to the left (right) target turning point, the duration of the flexion (extension) phase was shorter than that of the extension (flexion) phase, accompanied by higher flexion (extension) peak velocity. When gaze was fixated in between the two target turning points velocity profiles were symmetric. Tracking harmonicity was not significantly affected by gaze direction. 1988 1992 2003 2006 1999 2001 6 1988 2001 1988 2001 6 Musculoskeletal underpinnings of anchoring 1993 1990 1985 The temporal anchoring analysis revealed that movements were actively timed or anchored on maximal flexion with the wrist in a flexed posture and on maximal extension with the wrist in an extended posture. In either case, movement durations were shorter (and peak velocities larger) towards the anchored endpoint. Following a similar line of reasoning, the observed deviation from harmonicity in the Hooke’s portraits for a flexed (extended) wrist posture suggests that flexion (extension) movements are actively steered to a specific point in the perceptual-motor workspace (i.e., the movement cycle is anchored on maximal flexion (extension)), while the extension (flexion) half cycle simply serves to bring the hand out again for the next flexion (extension), perhaps in part passively through the release of potential energy stored in the elastic tissues around the wrist. The observed local and global features of tracking are surely consistent with such an interpretation. 1989 1992 1989 Visual underpinnings of anchoring 1995 1999 1979 1994 2000 2001 2002 2001 2005 2000 2001 2002 Theoretical implications with regard to anchoring 1989 1989 1992 1994 7 1989 2000 2000 2006 1989 2000 2000 2006 1989 2005 Coda 1989 2006 2007 2007 2007