Cavanaugh James, Alvarez Bryan D, Wurtz Robert H
Laboratory of Sensorimotor Research, National Eye Institute, National Institutes of Health, Bethesda, Maryland 20982-4435, USA.
J Neurosci. 2006 Nov 1;26(44):11347-58. doi: 10.1523/JNEUROSCI.2376-06.2006.
The premotor theory of visual spatial attention proposes that the same brain activity that prepares for saccades to one part of the visual field also facilitates visual processing at that same region of the visual field. Strong support comes from improvements in performance by electrical stimulation of presaccadic areas, including the frontal eye field and superior colliculus (SC). Interpretations of these stimulation experiments are hampered by the possibility that stimulation might be producing an internal visual flash or phosphene that attracts attention as a real flash would. We tested this phosphene hypothesis in the SC by comparing the effect of interchanging real visual stimuli and electrical stimulation. We first presented a veridical visual cue at the time SC stimulation improved performance; if a phosphene improved performance at this time, a real cue should do so in the same manner, but it did not. We then changed the time of SC visual-motor stimulation to when we ordinarily presented the veridical visual cue, and failed to improve performance. Last, we shifted the site of SC stimulation from the visual-motor neurons of the SC intermediate layers to the visual neurons of the superficial layers to determine whether stimulating visual neurons produced a larger improvement in performance, but it did not. Our experiments provide evidence that a phosphene is not responsible for the shift of attention that follows SC stimulation. This added evidence of a direct shift of attention is consistent with a key role of the SC in the premotor theory of attention.
视觉空间注意的运动前理论提出，为向视野的某一部分进行扫视做准备的相同大脑活动，也会促进在视野的同一区域进行视觉处理。来自对扫视前区域（包括额叶眼区和上丘（SC））进行电刺激后性能改善的有力支持。这些刺激实验的解释受到一种可能性的阻碍，即刺激可能会产生一种内部视觉闪光或光幻视，像真实闪光一样吸引注意力。我们通过比较互换真实视觉刺激和电刺激的效果，在SC中测试了这种光幻视假说。我们首先在SC刺激改善性能的时候呈现一个真实的视觉线索；如果此时光幻视能改善性能，那么真实线索应该也能以相同方式做到，但事实并非如此。然后我们将SC视觉运动刺激的时间改为我们通常呈现真实视觉线索的时间，性能并未改善。最后，我们将SC刺激的部位从SC中间层的视觉运动神经元转移到表层的视觉神经元，以确定刺激视觉神经元是否能在性能上产生更大的改善，但结果也没有。我们的实验提供了证据，表明光幻视并非SC刺激后注意力转移的原因。这种注意力直接转移的额外证据与SC在运动前注意理论中的关键作用是一致的。
