视觉信号有助于注视方向的编码。
Visual signals contribute to the coding of gaze direction.
作者信息
Blouin Jean, Amade Nicolas, Vercher Jean-Louis, Teasdale Normand, Gauthier Gabriel M
机构信息
UMR Mouvement & Perception, CNRS et Université de la Méditerranée, 163 Avenue de Luminy, Marseille, 13288 France.
出版信息
Exp Brain Res. 2002 Jun;144(3):281-92. doi: 10.1007/s00221-002-1029-5. Epub 2002 Apr 13.
Accurate information about gaze direction is required to direct the hand towards visual objects in the environment. In the present experiments, we tested whether retinal inputs affect the accuracy with which healthy subjects indicate their gaze direction with the unseen index finger after voluntary saccadic eye movements. In experiment 1, subjects produced a series of back and forth saccades (about eight) of self-selected magnitudes before positioning the eyes in a self-chosen direction to the right. The saccades were produced while facing one of four possible visual scenes: (1) complete darkness, (2) a scene composed of a single light-emitting diode (LED) located at 18 degrees to the right, (3) a visually enriched scene made up of three LEDs located at 0 degrees, 18 degrees and 36 degrees to the right, or (4) a normally illuminated scene where the lights in the experimental room were turned on. Subjects were then asked to indicate their gaze direction with their unseen index finger. In the conditions where the visual scenes were composed of LEDs, subjects were instructed to foveate or not foveate one of the LEDs with their last saccade. It was therefore possible to compare subjects' accuracy when pointing in the direction of their gaze in conditions with and without foveal stimulation. The results showed that the accuracy of the pointing movements decreased when subjects produced their saccades in a dark environment or in the presence of a single LED compared to when the saccades were generated in richer visual environments. Visual stimulation of the fovea did not increase subjects' accuracy when pointing in the direction of their gaze compared to conditions where there was only stimulation of the peripheral retina. Experiment 2 tested how the retinal signals could contribute to the coding of eye position after saccadic eye movements. More specifically, we tested whether the shift in the retinal image of the environment during the saccades provided information about the reached position of the eyes. Subjects produced their series of saccades while facing a visual environment made up of three LEDs. In some trials, the whole visual scene was displaced either 4.5 degrees to the left or 3 degrees to the right during the primary saccade. These displacements created mismatches between the shift of the retinal image of the environment and the extent of gaze deviation. The displacements of the visual scene were not perceived by the subjects because they occurred near the peak velocity of the saccade (saccadic suppression phenomenon). Pointing accuracy was not affected by the unperceived shifts of the visual scene. The results of these experiments suggest that the arm motor system receives more precise information about gaze direction when there is retinal stimulation than when there is none. They also suggest that the most relevant factor in defining gaze direction is not the retinal locus of the visual stimulation (that is peripheral or foveal) but rather the amount of visual information. Finally, the results suggest an enhanced egocentric encoding of gaze direction by the retinal inputs and do not support a retinotopic model for encoding gaze direction.
为了在环境中引导手部朝向视觉物体,需要准确的注视方向信息。在本实验中,我们测试了视网膜输入是否会影响健康受试者在自主扫视眼动后用未被看见的食指指示其注视方向的准确性。在实验1中,受试者先进行一系列自我选择幅度的来回扫视(约八次),然后将眼睛定位到右侧的一个自选方向。扫视过程中,受试者面对四种可能的视觉场景之一:(1)完全黑暗;(2)由位于右侧18度的单个发光二极管(LED)组成的场景;(3)由位于右侧0度、18度和36度的三个LED组成的视觉丰富场景;(4)实验房间灯光打开的正常照明场景。然后要求受试者用未被看见的食指指示其注视方向。在视觉场景由LED组成的条件下,受试者被指示在最后一次扫视时注视或不注视其中一个LED。因此,可以比较在有和没有中央凹刺激的条件下,受试者指向其注视方向时的准确性。结果表明,与在更丰富的视觉环境中产生扫视相比,当受试者在黑暗环境中或在单个LED存在的情况下产生扫视时,指向动作的准确性降低。与仅刺激周边视网膜的条件相比,中央凹的视觉刺激在受试者指向其注视方向时并没有提高准确性。实验2测试了视网膜信号如何在扫视眼动后对眼睛位置的编码做出贡献。更具体地说,我们测试了扫视过程中环境视网膜图像的移动是否提供了有关眼睛到达位置的信息。受试者在面对由三个LED组成的视觉环境时进行他们的一系列扫视。在一些试验中,在初次扫视期间,整个视觉场景向左移动4.5度或向右移动3度。这些移动导致环境视网膜图像的移动与注视偏差程度之间出现不匹配。受试者没有察觉到视觉场景的移动,因为它们发生在扫视的峰值速度附近(扫视抑制现象)。指向准确性不受视觉场景未被察觉的移动的影响。这些实验的结果表明,与没有视网膜刺激时相比,当存在视网膜刺激时,手臂运动系统接收到关于注视方向的更精确信息。它们还表明,定义注视方向的最相关因素不是视觉刺激的视网膜位置(即周边或中央凹),而是视觉信息量。最后,结果表明视网膜输入增强了以自我为中心的注视方向编码,并且不支持用于编码注视方向的视网膜拓扑模型。