Express saccades in distinct populations: east, west, and in‑between

P. C Knox, Felicity Wolohan, M S Helmy

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Express saccades are low latency (80–130 ms), visually guided saccades. While their occurrence is encour-aged by the use of gap tasks (the fixation target is extin-guished 200 ms prior to the saccade target appearing) and suppressed by the use of overlap tasks (the fixation target remains present when the saccade target appears), there are some healthy, adult participants, “express saccade makers” (ESMs), who persist in generating high proportions (> 30%) of express saccades in overlap conditions. These participants are encountered much more frequently in Chinese partici-pant groups than amongst the Caucasian participants tested to date. What is not known is whether this high number of ESMs is only a feature of Chinese participant groups. More broadly, there are few comparative studies of saccade behaviour across large participant groups drawn from dif-ferent populations. We, therefore, tested an independent group of 70 healthy adult Egyptian participants, using the same equipment and procedures as employed in the previous studies. Each participant was exposed to two blocks of 200 gap, and two blocks of 200 overlap trials, with block order counterbalanced. Results from the Schwartz Value Survey were used to confirm that this group of participants was culturally distinct from the Chinese and Caucasian (white British) groups tested previously. Fourteen percent (10/70) of this new group were ESMs, and the pattern of latency distribution in these ESMs was identical to that identified in the other participant groups, with a prominent peak in the express latency range in overlap conditions. Overall, we identified three modes in the distribution of saccade latency in overlap conditions, the timing of which (express peak at 110 ms, subsequent peaks at 160 and 210 ms) were strik-ingly consistent with our previous observations. That these behavioural patterns of saccade latency are observed con-sistently in large participant groups, drawn from geographi-cally, ethnically, and culturally distinct populations, suggests that they relate to the underlying architecture of the saccade system.
Original languageEnglish
JournalExperimental Brain Research
Early online date27 Sept 2017
Publication statusE-pub ahead of print - 27 Sept 2017


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