BarajasCaldwell
Introduction
Our eyes are constantly moving, even when observing a stationary object. In fact, there are two distinct types of movements: larger, sporadic scanning, called saccades; and much smaller, high frequency movements called ocular drift. Past experiments have suggested that saccades are responsible for preventing image fading on our retina— that these movements "refresh" our visual system so that we have continual neural responses to static scenes. This result has largely satisfied inquiries of the purpose of eye movements for the visual system, and many in the scientific community assume both types of eye movements serve the single purpose of preventing fading. However, Michele Rucci and Jonothan D. Victor argue that this is an oversimplification and that in particular, ocular drift serves the more profound role of amplifying higher spatial frequencies on the retina to improve visual resolution. Our work throughout this project centers on assessing this hypothesis.
Background
Literature focuses on ocular drift, which generally occurs in the period between the larger saccade movements, and is thus also referred to as "fixational" eye movement. Rucci and Victor estimate ocular drift has a mean speed of 50 minutes of arc per second, with a distribution of gaze position that disperses as time passes. An important idea of theirs is that these small motions cause fluctuations in luminance on the retina that would not be possible with a motionless eye. Since temporal fluctuations result in higher spectral power at the frequencies of the fluctuations, and since higher spectral power is associated with amplification of an image by the visual system, it follows that fixational eye movements can lead to visual amplification.
The above figure show Rucci and Victor's qualitative argument. The left plot shows higher modulations in luminance for faster eye movements, and the right plot shows their conclusion that retinal amplification increases with spatial frequency. An interesting result of theirs is that amplification stops increasing after about 30 cycles per degree. In our project we seek to support these plots with a more quantitative foundation.