Department of Neuroscience, Baylor College of Medicine, Houston, Texas, USA.
J Neurophysiol. 2010 Aug;104(2):960-71. doi: 10.1152/jn.01019.2009. Epub 2010 Jun 10.
It remains unclear how attention affects the tuning of individual neurons in visual cerebral cortex. Some observations suggest that attention preferentially enhances responses to low contrast stimuli, whereas others suggest that attention proportionally affects responses to all stimuli. Resolving how attention affects responses to different stimuli is essential for understanding the mechanism by which it acts. To explore the effects of attention on stimuli of different contrasts, we recorded from individual neurons in the middle temporal visual area (MT) of rhesus monkeys while shifting their attention between preferred and nonpreferred stimuli within their receptive fields. This configuration results in robust attentional modulation that makes it possible to readily distinguish whether attention acts preferentially on low contrast stimuli. We found no evidence for greater enhancement of low contrast stimuli. Instead, the strong attentional modulations were well explained by a model in which attention proportionally enhances responses to stimuli of all contrasts. These data, together with observations on the effects of attention on responses to other stimulus dimensions, suggest that the primary effect of attention in visual cortex may be to simply increase the strength of responses to all stimuli by the same proportion.
目前尚不清楚注意力如何影响视觉大脑皮层中单个神经元的调谐。一些观察结果表明，注意力优先增强对低对比度刺激的反应，而另一些则表明，注意力成比例地影响对所有刺激的反应。解决注意力如何影响对不同刺激的反应对于理解其作用机制至关重要。为了探索注意力对不同对比度刺激的影响，我们在恒河猴的中颞视觉区 (MT) 中记录单个神经元的反应，同时在其感受野内将注意力从首选刺激转移到非首选刺激。这种配置产生了强大的注意力调节作用，使得很容易区分注意力是否优先作用于低对比度刺激。我们没有发现低对比度刺激增强更大的证据。相反，一个模型很好地解释了强烈的注意力调节作用，该模型表明注意力成比例地增强了所有对比度刺激的反应。这些数据，以及对注意力对其他刺激维度反应的观察结果，表明注意力在视觉皮层中的主要作用可能是通过相同的比例简单地增加对所有刺激的反应强度。
