Peer Review #2 of "Age-related alterations in inhibitory control investigated using the minimally delayed oculomotor response task (v0.1)"

Abstract

Healthy, older adults are widely reported to experience cognitive decline, including impairments in inhibitory control. However, this general proposition has recently come under scrutiny because ageing effects are highly variable between individuals, are task dependent, and are sometimes not distinguished from general age-related slowing. We recently developed the minimally delayed oculomotor response (MDOR) task in which participants are presented with a simple visual target step, and instructed to saccade not to the target when it appears (a prosaccade response), but when it disappears (i.e. on target offset). Varying the target display duration prevents offset timing being predictable from the time of target onset, and saccades prior to the offset are counted as errors. A comparison of MDOR task performance in a group of 22 older adults (mean age 62y, range 50y to 72y) with that in a group of 39 younger adults (22y, range 19y-27y) demonstrated that MDOR latency was significantly increased in the older group by 34-68ms depending on target display duration. However, when MDOR latencies were corrected by subtracting the latency observed in a standard prosaccade task, the latency difference between groups was abolished. There was a larger latency modulation with target display duration in the older group which was observed even when their generally longer latencies were taken into account. Error rates were significantly increased in the older group. An analysis of the timing distribution of errors demonstrated that most errors were failures to inhibit responses to target onsets. When error distributions were used to isolate clear inhibition failures from other types of error, the older group still exhibited significantly higher error rates as well as a higher residual error rate. Although MDOR latency in older participants may largely reflect a general slowing in the oculomotor system with age, both the latency modulation and error rate results are consistent with an age-related inhibitory control deficit. How this relates to performance on other inhibitory control tasks remains to be investigated. PeerJ reviewing PDF | 24 25 Tel: 0151 794 9042 26 27 pcknox@liv.ac.uk 28 29PeerJ reviewing PDF | Abstract 31 Healthy, older adults are widely reported to experience cognitive decline, including 32 impairments in inhibitory control. However, this general proposition has recently come under 33 scrutiny because ageing effects are highly variable between individuals, are task dependent, 34 and are sometimes not distinguished from general age-related slowing. We recently developed 35 the minimally delayed oculomotor response (MDOR) task in which participants are presented 36 with a simple visual target step, and instructed to saccade not to the target when it appears (a 37 prosaccade response), but when it disappears (i.e. on target offset). Varying the target display 38 duration prevents offset timing being predictable from the time of target onset, and saccades 39 prior to the offset are counted as errors. A comparison of...