Spontaneous blinking is dependent on cognitive processes and is regulated by a central pacemaker that is highly sensitive to the attention demands and cognitive workload of the visual task in hand. There is evidence of a variability in the frequency of spontaneous blinking with differing amounts of cognitive workload, for example reading, computer work, during a conversation and in silent primary gaze. In addition, saccade eye movements are accompanied by a suppression of visual input. There is evidence to suggest that saccadic suppression is stronger for small gaze shifts (such as reading) but weaker with increasing saccade amplitude. Saccades have been found to be accompanied by a blink and occur in relation to large ocular movements. This study aimed to explore the joint influence of cognitive demands and large amplitude saccades on spontaneous blink rate. Twenty volunteers were recruited and instructed to follow a 60-minute real life driving circuit while a video camera recorded ocular movements and blinking. Each volunteer was taken through five different complexity levels to increase the amount of cognitive workload. They monitored spontaneous blink rate and horizontal saccades. Saccades were classified according to their amplitude and blink-saccade pairs were also recorded. The results showed consistent responses of spontaneous blink rates and saccades within the same complexity levels, although there was high inter-subject variability. At different complexity levels there was no statistically significant difference in spontaneous blink rate. However, the number of large amplitude gaze shifts increased with complexity levels. An average of 87.5% of large amplitude saccades were accompanied by a blink, so the study concludes that the number of blink-saccade pairs increased with higher complexity levels as well. This study shows that in complex dynamic visual settings, spontaneous blinking accompanied by large amplitude saccades plays a role in counteracting the reduction in blink rate associated with high cognitive demands.

Blinking and driving: the influence of saccades and cognitive workload.
Cardona G, Quevedo N.
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Khadijah Basheer

Moorfields Eye Hospital, London, UK.

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