Relationship between the Frequency of Microsaccade and Attentional State

It has been shown that the attentional state affects the properties of microsaccade. In this study, we investigated the relationship between the time courses of attentional state and of microsaccade frequency. In one experimental trial, one-digit random number (0–9) was sequentially presented within a preindicated area of the display and one of the numbers (test stimulus) was appeared in a different color. Participants were required to respond the numbers of the test stimulus. We manipulated the size and location of the area within which the stimuli were presented. In the trial, the attentional states before and after the test presentation should be relatively high and low, respectively. Microsaccades, defined as the saccades less than 1 degree of amplitude, were identified using an eye tracker with sampling frequency of 2000 Hz and the change of the frequency was analyzed offline. The result showed that the frequency of microsaccade decreased immediately after the test presentation and then increased relative to that before the test presentation. The size and location of attentional state did not affect the frequency of microsaccade systematically in the present experiments. These results suggest that the frequency of microsaccade could be an indicator of the strength of attention.