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L.A. Abel, M. Dirani; Effects of Age and Target Characteristics on Saccades to Remembered Targets . Invest. Ophthalmol. Vis. Sci. 2003;44(13):2130.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: To investigate and quantify the effects of age and fixation target disruption and enhancement on saccades to remembered targets. Fixation stimulus characteristics were altered to explore the effects on both the initiation of remembered saccades and on suppression of unwanted saccades. Methods: Two age groups (18-25 years and >59 years) participated. Eye movements were recorded using the Microguide infrared limbus tracker and digitised for later analysis. Tasks were 1) baseline memory-guided saccades, 2) similar, but with a 200 msec gap in the fixation target preceding the peripheral 50 msec target flash and 3) those where the 0.1 deg fixation target was enhanced with a 1.25 deg diameter surround of flickering and red/green alternating LEDs. 180 targets were presented at ±5 and 10° with delays preceding the cue to look at the remembered target location randomised over 1-2 seconds for all tasks. 2-way mixed design ANOVAs were used to examine the effects of age group and fixation target on both memory-guided saccade latency and on the number of errors produced. Latencies for incorrect saccades made on all tasks were also displayed on histograms for each age group. Results: Latencies on the baseline, gap and enhanced fixation trials were 289, 284 and 329 ms for young and 374, 342 and 390 ms for older subjects. ANOVA was significant for task but not group or interaction. Error counts were 27, 82 and 32 for young and 81, 160 and 65 for older subjects, on the 3 tasks, respectively. ANOVA was significant for both group and task, but there was no interaction. Analysis of error timing showed error latencies from express up to 1.9 sec; unexpectedly, the gap task produced large numbers of long-latency errors. The dynamic surround reduced the number of short (express and normal reflexive) latency errors compared to the baseline task. Conclusions: Ageing modestly increased latency of memory-guided saccades but roughly doubled the error rate. The gap reduced correct response latency only slightly but doubled error rates; it also appeared to disrupt fixation long after the central target reappeared. The surround appeared to modestly reduce peripheral target salience some of the time, but when errors did occur, they were still often of short latency, suggesting that it at times was a distractor. The multiple error latency peaks suggest independent failures of inhibition of express, normal reflexive and volitional saccades.
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