Gitelman Darren R, Parrish Todd B, Friston Karl J, Mesulam M-Marsel
The Northwestern Cognitive Brain Mapping Group, Cognitive Neurology and Alzheimer's Disease Center, Northwestern University Medical School, Chicago, Illinois 60611, USA.
Neuroimage. 2002 Apr;15(4):970-82. doi: 10.1006/nimg.2001.1006.
The ability to find targets embedded within complex visual environments requires the dynamic programming of visuomotor search behaviors. Functional magnetic resonance imaging was used to image subjects while they visually searched for targets embedded among foils. Visuomotor search activated the posterior parietal cortex and the frontal eye fields. Both regions showed a greater number of activated voxels on the right, consistent with the known pattern of right hemispheric dominance for spatial attention. The superior colliculus showed prominent activation in the search versus eye movement contrast, demonstrating, for the first time in humans, activation of this region specifically related to an exploratory attentional contingency. An analysis of effective connectivity demonstrated that the search-dependent variance in the activity of the superior colliculus was significantly influenced by the activity in a network of cortical regions including the right frontal eye fields and bilateral parietal and occipital cortices. These experiments also revealed the presence of a mosaic of activated sites within the frontal eye field region wherein saccadic eye movements, covert shifts of attention, and visuomotor search elicited overlapping but not identical zones of activation. In contrast to the existing literature on functional imaging, which has focused on covert shifts of spatial attention, this study helps to characterize the functional anatomy of overt spatial exploration.
在复杂视觉环境中寻找目标的能力需要对视觉运动搜索行为进行动态规划。研究人员使用功能磁共振成像对受试者在视觉上搜索夹杂在干扰物中的目标时进行成像。视觉运动搜索激活了顶叶后皮质和额叶眼区。这两个区域右侧激活的体素数量更多，这与已知的右半球在空间注意力方面占主导地位的模式一致。上丘在搜索与眼球运动的对比中显示出显著激活，首次在人类中证明了该区域的激活与探索性注意力偶发事件特别相关。有效连接性分析表明，上丘活动中依赖搜索的方差受到包括右侧额叶眼区以及双侧顶叶和枕叶皮质在内的皮质区域网络活动的显著影响。这些实验还揭示了额叶眼区区域内存在激活位点的镶嵌图，其中扫视眼球运动、注意力的隐蔽转移和视觉运动搜索引发了重叠但不完全相同的激活区域。与现有专注于空间注意力隐蔽转移的功能成像文献不同，本研究有助于描述公开空间探索的功能解剖结构。
