Derrington A M, Felisberti F
Department of Psychology, University Park, Nottingham, UK.
Vis Neurosci. 1998 Sep-Oct;15(5):875-80. doi: 10.1017/s0952523898155128.
The sudden displacement of the retinal image during a saccade raises the visual threshold of human observers to foveal stimuli. The fall in visual sensitivity observed during this phenomenon, known as saccadic suppression, seems to occur very early in the visual processing chain. The lateral geniculate nucleus (LGN) is a likely locus for the multiple retinal and extraretinal interactions occurring during saccadic eye movements, therefore we used the responses of relay cells of adult cats to simulate a psychophysical experiment. We first measured the responses of X and Y relay cells (27 X and 13 Y) to central spots of optimal size and different contrasts. The spots were presented either alone or time locked with the rapid movement of a large, high-contrast peripheral pattern, referred to as shift. We measured the percentage of trials on which the relay cell fired more spikes when the spot (contrast: 0.03-1.0) was present than when it was absent. In experiments with human observers the task was to indicate, by a keypress, which of two otherwise identical temporal intervals contained the spot. The shift reduces the sensitivity (raises the contrast threshold) of neurones in the cat relay cells to brief, stationary targets presented to the receptive-field center. The suppression of visual sensitivity is significantly greater in Y cells than in X cells (average sensitivity ratios 5.6 +/- 5.4 in Y cells, 1.59 +/- 0.9 in X cells: P < 0.001, U test). The shift also reduces the sensitivity of human observers to the same target. This suggests that the LGN is a potential locus for the modulation of visual responses that leads to saccadic suppression.
扫视过程中视网膜图像的突然移位会提高人类观察者对中央凹刺激的视觉阈值。在这种被称为扫视抑制的现象中观察到的视觉敏感度下降，似乎在视觉处理链的早期就会发生。外侧膝状体核（LGN）可能是扫视眼动过程中发生的多种视网膜和视网膜外相互作用的位点，因此我们利用成年猫中继细胞的反应来模拟一项心理物理学实验。我们首先测量了X和Y中继细胞（27个X细胞和13个Y细胞）对最佳大小和不同对比度的中央光斑的反应。光斑单独呈现，或者与一个大的、高对比度的外周图案的快速移动（称为移位）进行时间锁定呈现。我们测量了中继细胞在光斑（对比度：0.03 - 1.0）存在时比不存在时发放更多峰电位的试验百分比。在针对人类观察者的实验中，任务是通过按键指出两个其他方面相同的时间间隔中哪一个包含光斑。移位降低了猫中继细胞中神经元对呈现于感受野中心的短暂、静止目标的敏感度（提高了对比度阈值）。Y细胞中视觉敏感度的抑制明显大于X细胞（Y细胞的平均敏感度比率为5.6 +/- 5.4，X细胞为1.59 +/- 0.9：P < 0.001，U检验）。移位也降低了人类观察者对相同目标的敏感度。这表明外侧膝状体核是导致扫视抑制的视觉反应调制的一个潜在位点。
