Fixational eye movement correction of blink-induced gaze position errors.

Michael B Mccamy,Jorge Otero-Millan,Susana Martinez-Conde,Kevin Paterson,Francisco M Costela,Xoana G Troncoso,Stephen L Macknik,Sharon M Crook,Ali Najafian Jazi

doi:10.1371/journal.pone.0110889

Abstract

Our eyes move continuously. Even when we attempt to fix our gaze, we produce “fixational” eye movements including microsaccades, drift and tremor. The potential role of microsaccades versus drifts in the control of eye position has been debated for decades and remains in question today. Here we set out to determine the corrective functions of microsaccades and drifts on gaze-position errors due to blinks in non-human primates (Macaca mulatta) and humans. Our results show that blinks contribute to the instability of gaze during fixation, and that microsaccades, but not drifts, correct fixation errors introduced by blinks. These findings provide new insights about eye position control during fixation, and indicate a more general role of microsaccades in fixation correction than thought previously.

Highlights

The role of microsaccades in the control and correction of fixation position has been controversial for over 50 years [1,2,3,4]
Current findings support a combined role of neural noise and fixation error in triggering microsaccades during attempted fixation, with the contribution of each signal depending on the magnitude of the gaze position error [7]
Spontaneous blinks resulted in fixation errors of moderate size (0.88+/20.45 deg on average), where the eye position at the end of a blink did not match the position of the fixation target (Figure 2; Table 1)

Summary

Introduction

The role of microsaccades in the control and correction of fixation position has been controversial for over 50 years [1,2,3,4]. By the end of the 1970 s, most of the field agreed that microsaccades were not necessary for the control of fixation position, whereas drift ( called slow control) served that purpose (see [4] for a historical review). This conclusion remained uncontested until the early 2000 s, when new analyses indicated that microsaccades introduce fixation errors on a short timescale, and correct fixation errors on a longer timescale [6]. If a subject’s gaze deviates from the target by ,0.5u or more, corrective microsaccades might rectify the error [5,8], whereas if the fixation error is small or insignificant, neural noise might trigger subsequent microsaccades instead [7]

Methods

Results

Conclusion