Movement structure in young and elderly adults during goal-directed movements of the left and right arm

Abstract

Elderly adults often exhibit performance deficits during goal-directed movements of the dominant arm compared with young adults. Recent studies involving hemispheric lateralization have provided evidence that the dominant and non-dominant hemisphere-arm systems are specialized for controlling different movement parameters and that hemispheric specialization may be reduced during normal aging. The purpose was to examine age-related differences in the movement structure for the dominant (right) and non-dominant (left) during goal-directed movements. Young and elderly adults performed 72 aiming movements as fast and as accurately as possible to visual targets with both arms. The findings suggest that previous research utilizing the dominant arm can be generalized to the non-dominant arm because performance was similar for the two arms. However, as expected, the elderly adults showed shorter relative primary submovement lengths and longer relative primary submovement durations, reaction times, movement durations, and normalized jerk scores compared to the young adults.

Fig. 1

Experimental arrangement. Subjects were seated and facing a monitor with a digitizer tablet positioned on a table between the subject and the monitor. Vision of the entire arm was occluded by an opaque shield (dashed square) placed over the arm and digitizer. Subjects were required to make point-to-point drawing movements with an inkless pen between the start position and various targets displayed on the monitor. Visual feedback of the target, pen position, and movement trajectory were provided via the computer monitor during each trial.

Fig. 2

Experimental presentation. A. The start of the experiment. B. Execution of a trial. C. Possible left and right target locations were at angles of 5, 45, and 85 degrees of the subject’midline. Thus, a total of six target positions were employed (left 5, 45, 85 degrees, and right 5, 45, and 85 degrees). All targets were located 13.4 cm from the start position (same index of difficulty for all targets). The target had a diameter of 0.6 cm diameter and remained constant throughout all experimental conditions.

Fig. 3

Reaction time for young and elderly adults, the left and right hands, and the left and right locations. Values are means ± SE. Reaction time was longer for the elderly compared with the young adults, similar for the left and right arms, and longer for the left compared with the right location. *indicates significant (p < 0.05) between groups or locations.

Fig. 4

Movement time and movement velocity for young and elderly adults, the left and right hands, and the left and right locations. A. Movement time was greater for the elderly compared with the young adults, similar for the left and right arms, and greater for the right compared with the left location. B. Movement velocity was greater for the elderly compared with the young adults, similar for the left and right arms, and greater for the left compared with the right location. C. There was a significant arm × location interaction, which indicated that the movement time was greater when each arm moved to the corresponding contralateral location. D. There was a significant arm × location interaction, which indicated that the movement velocity was lower when each arm moved to the corresponding contralateral location. *indicates significant (p < 0.05) between groups or locations

Fig. 5

Relative primary submovement length and duration for young and elderly adults, the left and right hands, and the left and right locations. Values are means ± SE. A. Relative primary submovement length was greater for the young compared with the elderly adults, similar for the left and right arms, and greater for the left compared with the right location. B. Relative primary submovement duration was greater for the young compared with the elderly adults, similar for the left and right arms, and greater for the left compared with the right location. C. There was a significant arm × location interaction, which indicated that the relative primary submovement duration was greater when each arm moved to the corresponding contralateral location. *indicates significant (p < 0.05) between groups or locations.

Fig. 6

Normalized jerk for young and elderly adults, the left and right hands, and the left and right locations. Values are means ± SE. The normalized jerk was greater for the elderly compared with the young adults, similar for the left and right arms, and similar for the left and right locations. *indicates significant (p < 0.05) between groups.