The influence of gaze stabilization and fixation on stepping reactions in younger and older adults.
OBJECTIVE
To date, there has been little evidence to suggest the importance of foveal viewing versus peripheral retina viewing when trying to recover from a perturbation. The purposes of this investigation were to (1) determine whether a visual target can be stabilized on the fovea during a perturbation, (2) determine whether stepping responses following a perturbation are influenced by foveal fixation, and (3) compare gaze stability and stepping responses between young and aging adults.


METHODS
Ten young adults and 10 aging adults were asked to wear an eye-tracking device linked to a kinematic tracking system during perturbations. Perturbations were delivered under 2 conditions: control (no instructions regarding gaze location were given) and earth-fixed (EF) (subjects were asked to fixate gaze on an EF target). Stepping responses were recorded via force plates. Gaze stability, reported as percent foveal fixation (% FF), was calculated from eye-tracking data. Step latencies (SLs) were computed from force plate data. A 2 x 2 analysis of variance was used to assess statistical significance between groups. For the young and aging adults, linear correlations were made to identify relationships between % FF and SL.


RESULTS
For each condition, aging adults took longer to initiate a step (control, P = .002; EF, P = .003). Young adults were better at maintaining gaze fixation than older adults (P = .0045). Linear correlations demonstrated significant negative relationships between SL and % FF for young (r = -0.76, P = .001) and older (r = -0.87, P = .0001) adults. As % FF increased, SL decreased.


CONCLUSIONS
The ability to maintain gaze fixation of an EF target may be important in reducing SL following a perturbation. Older adult subjects demonstrated a decreased ability to fixate a target during balance tasks while also displaying longer SLs.
Diehl
M Dyer
MD
Krannert School of Physical Therapy, University of Indianapolis, Indianapolis, IN 46227, USA. diehlm@uindy.edu
Pidcoe
Peter E
PE
D000058:Accidental Falls / Q000517:prevention & control; D000328:Adult; D000368:Aged; D000704:Analysis of Variance; D053483:Eye Movement Measurements; D005260:Female; D005403:Fixation, Ocular / Q000502:physiology*; D006801:Humans; D008124:Locomotion / Q000502:physiology*; D008297:Male; D004856:Postural Balance / Q000502:physiology*; D011597:Psychomotor Performance / Q000502:physiology