Fig. 6.

Consistency of vigor across head and arm movements. A: average velocity profile for head and arm movements for two representative subjects. The displacements are between 13–15 deg (head) and 15–18 cm (arm) in the plotted trials. Error bars are within-subject SD across trials. B: peak velocity vs. amplitude relationship of arm movements and head movements for 2 representative subjects. Data for subjects 32GT and 35PV are shown in gray and black, with lines of best fit shown in black and gray. For each subject, we fit a line constrained to pass through the origin. The fit across all participants is shown as a dashed line (population). Each point represents a single movement. C: the term “vigor” refers to the relationship between each individual’s amplitude-velocity function with respect to the population. Plots show the distribution of head (left) and arm (right) vigor. D: relationship between vigor of head movements and arm movements. Each point represents a single subject. Certain subjects (n = 9) did not move their head during the gaze shift, and therefore we could not estimate vigor of head movements for those subjects. Across subjects that we could estimate head vigor (n = 28), we found a strong correspondence between vigor of head and arm movements (R = 0.83, P < 0.001).