Department of Neurobiology, Stanford University, Stanford, California 94305, USA.
J Neurosci. 2010 Feb 3;30(5):1727-38. doi: 10.1523/JNEUROSCI.3740-09.2010.
Stimulus selection for gaze and spatial attention involves competition among stimuli across sensory modalities and across all of space. We demonstrate that such cross-modal, global competition takes place in the intermediate and deep layers of the optic tectum, a structure known to be involved in gaze control and attention. A variety of either visual or auditory stimuli located anywhere outside of a neuron's receptive field (RF) were shown to suppress or completely eliminate responses to a visual stimulus located inside the RF in nitrous oxide sedated owls. The essential mechanism underlying this stimulus competition is global, divisive inhibition. Unlike the effect of the classical inhibitory surround, which decreases with distance from the RF center and shapes neuronal responses to individual stimuli, global inhibition acts across the entirety of space and modulates responses primarily in the context of multiple stimuli. Whereas the source of this global inhibition is as yet unknown, our data indicate that different networks mediate the classical surround and global inhibition. We hypothesize that this global, cross-modal inhibition, which acts automatically in a bottom-up manner even in sedated animals, is critical to the creation of a map of stimulus salience in the optic tectum.
眼动和空间注意的刺激选择涉及跨感觉模态和整个空间的刺激竞争。我们证明，这种跨模态、全局竞争发生在视顶盖的中间和深层，视顶盖是已知参与眼球控制和注意的结构。各种位于神经元感受野（RF）之外的视觉或听觉刺激被证明可以抑制或完全消除位于 RF 内的视觉刺激的反应在一氧化二氮镇静的猫头鹰。这种刺激竞争的基本机制是全局的、分散的抑制。与经典抑制环绕的作用不同，经典抑制环绕的作用随 RF 中心的距离而减小，并塑造神经元对单个刺激的反应，全局抑制作用跨越整个空间，并主要在多个刺激的背景下调节反应。虽然这种全局抑制的来源尚不清楚，但我们的数据表明，不同的网络介导了经典的环绕和全局抑制。我们假设，这种全局的、跨模态的抑制，即使在镇静的动物中也以自下而上的方式自动作用，对于在视顶盖中创建刺激显着性的地图至关重要。
