McAlonan Kerry, Cavanaugh James, Wurtz Robert H
Laboratory of Sensorimotor Research, National Eye Institute, National Institutes of Health, Bethesda, Maryland 20892, USA.
Nature. 2008 Nov 20;456(7220):391-4. doi: 10.1038/nature07382. Epub 2008 Oct 5.
The massive visual input from the eye to the brain requires selective processing of some visual information at the expense of other information, a process referred to as visual attention. Increases in the responses of visual neurons with attention have been extensively studied along the visual processing streams in monkey cerebral cortex, from primary visual areas to parietal and frontal cortex. Here we show, by recording neurons in attending macaque monkeys (Macaca mulatta), that attention modulates visual signals before they even reach cortex by increasing responses of both magnocellular and parvocellular neurons in the first relay between retina and cortex, the lateral geniculate nucleus (LGN). At the same time, attention decreases neuronal responses in the adjacent thalamic reticular nucleus (TRN). Crick argued for such modulation of the LGN by observing that it is inhibited by the TRN, and suggested that "if the thalamus is the gateway to the cortex, the reticular complex might be described as the guardian of the gateway", a reciprocal relationship we now show to be more than just hypothesis. The reciprocal modulation in LGN and TRN appears only during the initial visual response, but the modulation of LGN reappears later in the response, suggesting separate early and late sources of attentional modulation in LGN.
从眼睛到大脑的海量视觉输入需要对某些视觉信息进行选择性处理，而忽略其他信息，这一过程被称为视觉注意力。沿着猴子大脑皮层的视觉处理流，从初级视觉区域到顶叶和额叶皮层，视觉神经元因注意力而产生的反应增强已得到广泛研究。在这里，我们通过记录处于注意力状态下的猕猴（恒河猴）的神经元发现，注意力在视觉信号甚至还未到达皮层之前就对其进行调制，方法是增强视网膜与皮层之间的首个中继站——外侧膝状体核（LGN）中大细胞和小细胞神经元的反应。与此同时，注意力会降低相邻丘脑网状核（TRN）中的神经元反应。克里克通过观察到LGN受TRN抑制，进而提出了对LGN的这种调制作用，并认为“如果丘脑是通向皮层的门户，那么网状复合体或许可被描述为门户的守护者”，我们现在证明这种相互关系不仅仅是一种假设。LGN和TRN中的相互调制仅在最初的视觉反应期间出现，但LGN的调制在反应后期会再次出现，这表明LGN中存在早期和晚期注意力调制的不同来源。
