Rucci Michele, Iovin Ramon, Poletti Martina, Santini Fabrizio
Department of Cognitive and Neural Systems, Boston University, Boston, Massachusetts 02215, USA.
Nature. 2007 Jun 14;447(7146):851-4. doi: 10.1038/nature05866.
Our eyes are constantly in motion. Even during visual fixation, small eye movements continually jitter the location of gaze. It is known that visual percepts tend to fade when retinal image motion is eliminated in the laboratory. However, it has long been debated whether, during natural viewing, fixational eye movements have functions in addition to preventing the visual scene from fading. In this study, we analysed the influence in humans of fixational eye movements on the discrimination of gratings masked by noise that has a power spectrum similar to that of natural images. Using a new method of retinal image stabilization, we selectively eliminated the motion of the retinal image that normally occurs during the intersaccadic intervals of visual fixation. Here we show that fixational eye movements improve discrimination of high spatial frequency stimuli, but not of low spatial frequency stimuli. This improvement originates from the temporal modulations introduced by fixational eye movements in the visual input to the retina, which emphasize the high spatial frequency harmonics of the stimulus. In a natural visual world dominated by low spatial frequencies, fixational eye movements appear to constitute an effective sampling strategy by which the visual system enhances the processing of spatial detail.
我们的眼睛一直在运动。即使在视觉注视期间，微小的眼球运动也会不断使注视位置产生抖动。众所周知，在实验室中消除视网膜图像运动时，视觉感知往往会消退。然而，长期以来一直存在争议的是，在自然观看过程中，注视性眼球运动除了防止视觉场景消退之外是否还有其他功能。在这项研究中，我们分析了注视性眼球运动对人类辨别被具有与自然图像相似功率谱的噪声掩盖的光栅的影响。使用一种新的视网膜图像稳定方法，我们选择性地消除了在视觉注视的扫视间隔期间正常发生的视网膜图像运动。在这里我们表明，注视性眼球运动提高了对高空间频率刺激的辨别能力，但对低空间频率刺激则不然。这种提高源于注视性眼球运动在视网膜视觉输入中引入的时间调制，它强调了刺激的高空间频率谐波。在一个由低空间频率主导的自然视觉世界中，注视性眼球运动似乎构成了一种有效的采样策略，通过这种策略视觉系统增强了对空间细节的处理。
