Abstract
Microsaccade (MS) is the largest and fastest component of fixational eye movements. Recently, several behavioral studies have attempted to establish links between microsaccade and various cognitive activities. In this study, we examined the relationship between cognitive load and MS rate. While studies linking MS rate with cognitive activities typically employed visual tasks, in this study, we examined MS rate in a mental arithmetic task, where, after initial visual presentation of the calculation required, visual processing was no longer required during the actual calculation. Cognitive load was manipulated by varying number of digits involved in the calculation. We used the time it took to finish the task (response time, RT) as the indicator for cognitive load. We also recorded pupil size which has been linked to cognitive load. After a display of a fixation spot, two numbers were presented sequentially on the center of the screen. Before and after the display of these two numbers, an operational sign ("+"for addition; "-"for subtraction) was also displayed on the center of the screen. Participants made a verbal response as soon as they finished the calculation. We found that MS rates immediately following calculation increased to and maintained for a period of time at a level about twice of that during calculation. During calculation, MS rates were higher for trials with longer RTs (linear regression r = 0.57, p=0.016), while after calculation MS rate were much less affected by RTs. Moreover, during calculation, pupil size increased. Following calculation, pupil size continued to increase for a short period of time then decreased. The peak pupil sizes were higher for longer RTs (linear regression r = 0.42, p=0.0001). The results of this study, for the first time, demonstrated that that both MS rate and pupil size are affected by the cognitive load during the arithmetic task.
Meeting abstract presented at VSS 2013