Saccadic latency differences in preclinical Alzheimer’s disease

Abstract Background Previous studies indicate that individuals with mild cognitive impairment (MCI) or Alzheimer’s disease (AD) have higher latencies on anti‐saccade tasks than healthy controls. We investigated whether this difference in latency appears even earlier, in cognitively healthy (CH) individuals at high risk of cognitive decline to MCI or AD and whether subliminal priming or task switching further impacted this latency difference. Method We studied CH participants whose cerebrospinal fluid (CSF) amyloid / tau ratio was normal (≥2.7132, low risk) or pathological (<2.7132, high risk) (PMID: 24260210). The testing paradigm included three blocks: (1) all saccades, (2) all anti‐saccades, and (3) patterned task switching with two saccades followed by two anti‐saccades. Trials began with a green (saccade) or red (anti‐saccade) cue appearing at a central fixation point. Then, a masked subliminal cue appeared on the right or left, followed by a target congruent or incongruent with the subliminal prime location. Trials ended 1000 ms after the participant first looked directly at the target for saccade trials or away from the target for anti‐saccade trials. Result Preliminary results (n = 19, 3 high risk) using a 3‐way mixed ANOVA (d.f. = 3484) indicate that high risk participants perform slower across all conditions (F = 26.36, p <<< 0.001). This effect is especially pronounced when task switching (F = 3.41, p < 0.05), with high risk participants performing 70.9 ms slower in the task switching block (Bonferroni‐corrected p = 6.62×10 −6 , 95% CI = [29.8, 112]). During the block with all anti‐saccades, however, the difference in performance is not significant (Bonferroni‐corrected p = 0.78), unlike the effects previously observed in individuals with MCI or AD. Additionally, subliminal cues do not show a significant overall effect on behavioral data (F = 2.32, p = 0.13). Conclusion Pilot results indicate that latency differences when task switching between saccade and anti‐saccade tasks exist in CH people at high risk of cognitive decline. Because eye tracking tasks are much less invasive and expensive than spinal taps, they could provide a potential screening tool for those at risk of cognitive decline.