Iris Group, LPPA CNRS-Collège de France, Paris, France.
Brain Res. 2010 Mar 19;1321:105-16. doi: 10.1016/j.brainres.2010.01.002. Epub 2010 Jan 14.
Previous studies have shown that upward saccade latencies are faster than downward saccade latencies in certain tasks. This asymmetry does not appear to represent a general main effect of the visual, or the vertical oculomotor system. In this study we examined the cortical activity underlying this latency asymmetry. We used MEG to assess cortical activity related to horizontal and vertical saccade preparation, and eye movement recordings to assess saccade latencies in a modified delay task. The reconstructed cortical activity was examined with respect to the onset of the target stimulus and the onset of the saccade. Upward saccades were faster than downward saccades, in agreement with previous studies. Although to a large extent, horizontal and vertical targets activated similar areas, there were also some differences. The earlier difference was found 100-150 ms after target onset over the right supramarginal gyrus when subjects attended to location-cues. Down cues activated this area faster than up cues. Moreover, cue-related activity was stronger over the left frontal cortex for up than down cues. In contrast, saccade-related activity over the same area was stronger when preceding downward than upward saccades. The results suggest that stimuli in the upper and lower visual field may have different impacts on accessing networks related to visual attention and motor preparation resulting in different behavioral asymmetries.
先前的研究表明，在某些任务中，上眼跳潜伏期快于下眼跳潜伏期。这种不对称似乎并不代表视觉或垂直眼球运动系统的一般主要效应。在这项研究中，我们研究了这种潜伏期不对称的皮层活动基础。我们使用 MEG 来评估与水平和垂直眼跳准备相关的皮层活动，并使用眼动记录来评估在修改后的延迟任务中眼跳潜伏期。重建的皮层活动与目标刺激的开始和眼跳的开始有关。与先前的研究一致，上眼跳比下眼跳快。尽管在很大程度上，水平和垂直目标激活了相似的区域，但也存在一些差异。当受试者注意位置提示时，在目标出现后 100-150 毫秒，右侧缘上回出现更早的差异，下提示比上提示更快地激活该区域。此外，对于上提示，提示相关活动在左额叶皮层更强。相比之下，当先前的眼跳是向下的而不是向上的时，相同区域的眼跳相关活动更强。研究结果表明，上视野和下视野中的刺激可能对与视觉注意力和运动准备相关的网络有不同的影响，从而导致不同的行为不对称。
