Control of eye position.

A, B. Eye position during the period of S2 presentation for the example cell of Fig 3. Each point is the mean eye position during the period of 20ms of S2 presentation in the conditions of S2-alone (A) and S1-S2 sequence with the SOA of 100ms (B). C. Horizontal (real) and vertical (dotted) eye positions during an example trial. Two vertical real lines indicate the times of S1 (earlier) and S2 (later) onset with the SOA of 30ms. Two vertical dashed lines indicate the analysis window of 300ms for counting microsaccades starting from -100ms to 200ms of S1 onset. D. Velocity of radial eye position with a threshold of 15 deg/s (horizontal dashed line). Four real and dashed vertical lines are same as in A. Three inverted triangles point the peak radial velocity of three movements that were taken as microsaccades. Two consecutive peaks with an inter-peak interval shorter than 100ms, such as shown near 800ms sometimes occurred, the first of which was considered as one microsaccade. E. Acceleration signal of radial eye position for determining onset and offset of microsaccades. F. Rate of microsaccade occurrence during the analysis window of 300ms across SOA conditions. (EPS)