Abstract
Purpose :
To examine the effect of healthy aging on the inhibitory control of saccades, smooth pursuit and optokinetic nystagmus (OKN) suppression. The relationships between inhibition failures of different eye movements were investigated, to examine the degree to which a common process underlies inhibitory control across tasks.
Methods :
19 younger (18-30 years) and 14 older (62-78 years) healthy individuals participated. Experiment 1 consisted of 3 baseline tasks: reflexive saccades, smooth pursuit and OKN suppression. Experiment 2 consisted of 3 tasks with increased inhibitory demands: anti-saccades, pursuit against a photographic background and OKN suppression with moving feature detection. Dependent variables were error rate, latency, peak velocity and gain for saccades, gain and time off-target for pursuit and gain for OKN suppression. Mixed ANOVAs were used to examine the effects of age and task demands. Pearson’s correlation was conducted between dependent variables whilst controlling for age: error rate, time off-target and OKN gain.
Results :
In Experiment 1, only saccadic latency differed between younger (161.08 ± 21.23ms) and older groups (186.11 ± 25.57ms) (p = 0.006); In Experiment 2, older adults showed poorer inhibition compared to younger adults, with higher anti-saccade error rates (34.57 ± 24.05% vs 19.37 ± 11.59%, p = 0.02), more time off-target during smooth pursuit (726.46 ± 441.45ms vs 376.35 ± 321.59ms, p = 0.001), and higher OKN gain (i.e., poorer suppression) during background feature detection (0.46 ± 0.17 vs 0.22 ± 0.11, p < 0.001). Moreover, there were strong, positive relationships between saccade error rate and pursuit time off-target (r = 0.71, p < 0.001); error rate and OKN gain (r = 0.61, p < 0.001); and time off-target and OKN gain (r = 0.7, p < 0.001).
Conclusions :
This study demonstrated that older adults have diminished inhibitory control across several eye movement tasks which contained competing demands on subjects’ attention, while their simpler versions were almost unaffected by age. The strong relationships between inhibitory measures suggest that there is a common mechanism mediating inhibition control of different eye movements, which declines with age. Future studies with a range of tasks and intermediate aged subjects could examine what degree of task complexity begins to impair performance, and at which age it occurs.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.