Age differences in kinesthetic and static-position sense of the upper limb in unconstrained 3-D tasks

Christopher Ross Coffman

doi:10.17077/etd.t586t6t0

We compared sense of movement and position in unconstrained 3-dimensional tasks in younger and older adults to investigate whether older adults have diminished kinesthetic sense. Active and passive kinesthesia were compared in a novel dynamic-position sense task and also in a static-position sense task. Older (65-85 years) and younger (18-22) adults performed tasks in which they moved the right arm to touch the right index tip to the moving and stationary left index (target) fingertip in different conditions. In the dynamic task the participant or experimenter moved the left upper limb and, after a variable delay, the subject moved the right arm to attempt to touch the right index-tip to the moving target index-tip. Participants performed the dynamic task with vision actively moving both limbs (VDA), without vision while actively moving both limbs (NVDA), and without vision with the experimenter moving the target limb (NVDP). In the static task the participant (NVSA) or experimenter (NVSP) moved the target limb to a position and held it stationary while the participant moved the right arm to attempt to touch the right index tip to the target fingertip. Both younger and older adults performed the dynamic task remarkably accurately with errors averaging less than 1.6 cm across the 3 conditions. Mean 3-dimensional distance errors averaged slightly (0.19 cm) larger in older adults in the dynamic task (F₁,₂₅=5.88, p=0.02). Variable distance errors did not differ between age groups in the dynamic task (F₁,₂₅=0.90, p=0.35). Small errors were observed in all conditions. NVDP had the largest mean distance errors (1.81 cm) of moving conditions, followed by NVDA (1.65 cm), and VDA had the smallest errors (1.27 cm) (F₂,₅₀=49.55, pcorr< .001, all post hoc tests less than p< 0.05). There was no evidence of errors depending on target index-tip peak speed or location. Interestingly, distance errors in the static tasks averaged 3.0 cm and were clearly larger than in the dynamic tasks (F₁,₂₅=57.78, p< 0.001). Within the two static conditions, average errors were 0.5 cm larger in the NVSP condition than in the NVSA condition (F₁,₂₅=7.56, p=0.01). Average distance errors trended to being larger in older adults in static conditions (F₁,₂₅=3.53, p=0.07). Variable distance errors were similar for the two age groups in the static conditions (F₁,₂₅=.25, p=0.35), averaging 1.77 cm in NVSP and 1.38 cm in NVSA (F₁,₂₅=.7.98, p< 0.01). These results suggest that regardless of age, availability of visual information, active/passive target limb movement, or reaching to static versus moving targets that adults are generally quite accurate at localizing fingertip position. The finding that accuracy in the static and dynamic tasks when vision was not allowed was only slightly better when the subjects actively moved the target arm (i.e., NVDA, NVSA) than when the target arm was moved by the experimenter (NVDP, NVSP) indicates that internal models may contribute only very slightly to proprioceptive localization of the upper limb. However, it is clear that kinesthetic sensory information from the periphery is sufficient to allow the central nervous system to accurately calculate position of the endpoint of the limb (tip of the index) while unconstrained in 3-dimensional space.

Age differences in kinesthetic and static-position sense of the upper limb in unconstrained 3-D tasks

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