Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada.
J Neurophysiol. 2012 Nov;108(10):2653-67. doi: 10.1152/jn.00389.2012. Epub 2012 Aug 29.
Saccades are useful for directing the high-acuity fovea to visual targets that are of behavioral relevance. The selection of visual targets for eye movements involves the superior colliculus (SC), where many neurons respond to visual stimuli. Many of these neurons are also activated before and during saccades of specific directions and amplitudes. Although the role of the SC in controlling eye movements has been thoroughly examined, far less is known about the nature of the visual responses in this area. We have, therefore, recorded from neurons in the intermediate layers of the macaque SC, while using a sparse-noise mapping procedure to obtain a detailed characterization of the spatiotemporal structure of visual receptive fields. We find that SC responses to flashed visual stimuli start roughly 50 ms after the onset of the stimulus and last for on average ~70 ms. About 50% of these neurons are strongly suppressed by visual stimuli flashed at certain locations flanking the excitatory center, and the spatiotemporal pattern of suppression exerts a predictable influence on the timing of saccades. This suppression may, therefore, contribute to the filtering of distractor stimuli during target selection. We also find that saccades affect the processing of visual stimuli by SC neurons in a manner that is quite similar to the saccadic suppression and postsaccadic enhancement that has been observed in the cortex and in perception. However, in contrast to what has been observed in the cortex, decreased visual sensitivity was generally associated with increased firing rates, while increased sensitivity was associated with decreased firing rates. Overall, these results suggest that the processing of visual stimuli by SC receptive fields can influence oculomotor behavior and that oculomotor signals originating in the SC can shape perisaccadic visual perception.
扫视对于将高敏度的中央凹引导至与行为相关的视觉目标非常有用。眼球运动的视觉目标选择涉及上丘（SC），其中许多神经元对视觉刺激做出反应。许多这些神经元在前向和进行特定方向和幅度的扫视期间也被激活。虽然 SC 在控制眼球运动中的作用已经被彻底研究，但关于该区域的视觉反应的性质却知之甚少。因此，我们记录了猕猴 SC 中间层的神经元，同时使用稀疏噪声映射程序获得视觉感受野的时空结构的详细特征。我们发现，对闪烁视觉刺激的 SC 反应在刺激开始后大约 50 毫秒开始，并持续约 70 毫秒。大约 50%的这些神经元在兴奋中心周围的某些位置闪烁的视觉刺激下受到强烈抑制，抑制的时空模式对扫视的时间产生可预测的影响。因此，这种抑制可能有助于在目标选择期间过滤分心刺激。我们还发现，扫视以与在皮层和知觉中观察到的扫视抑制和后扫视增强非常相似的方式影响 SC 神经元对视觉刺激的处理。然而，与皮层观察到的情况相反，视觉敏感性的降低通常与放电率的增加相关，而敏感性的增加与放电率的降低相关。总的来说，这些结果表明，SC 感受野对视觉刺激的处理可以影响眼球运动行为，并且起源于 SC 的眼球运动信号可以塑造扫视前的视觉感知。
